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1
Marshall, Susan, Robert J. Oglesby, and Anne W. Nolin. "Effect of western U.S. snow cover on climate." Annals of Glaciology 32 (2001): 82–86. http://dx.doi.org/10.3189/172756401781819229.
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AbstractThe purpose of this study is to identify characterize and quantify local, regional and remote effects of snow cover on western U. S. climate and water resources. An ensemble of predictability and sensitivity studies was made with the U.S. National Center for Atmospheric Research (NCAR) Community Climate Model, version 3 (CCM3) to investigate the relative roles of snow-cover anomalies and initial atmospheric states in the subsequent accumulation and ablation seasons. The suite of model experiments focuses on the direct effect of snow on regional climate anomalies and ultimately will be used to examine the lagged effect of anomalous snow cover on the climate. The set of ensemble simulations presented here looks at the climate-system response to anomalously high and low snow cover at the start of the ablation season over the western U.S.A. These current results suggest that the initial state of snow cover is more important than the initial state of the atmosphere or of sea-surface temperatures because of direct thermal effects on the surface and subsequent indirect, dynamical effects on the atmospheric circulation.
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Simecek-Beatty, Debra, William J. Lehr, and Jeffery Lankford. "Leaking Tank Experiments for Heavy Oils." International Oil Spill Conference Proceedings 2001, no. 1 (March 1, 2001): 127–31. http://dx.doi.org/10.7901/2169-3358-2001-1-127.
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ABSTRACT During oil spill incidents involving damaged tankers, the amount of product released may be uncertain. Many accidents occur under adverse conditions, so determining the volume lost by sounding the tanks may not be practical. In the first few hours, initial volume estimates often are based on visual observations of the resulting slick, a notoriously unreliable approach. Oils that have special characteristics, such as group V oils and Orimulsion®, that may or may not result in a surface slick, further complicate this problem. The Hazardous Materials Response Division of the National Oceanic and Atmospheric Administration (NOAA/HAZMAT) has developed a leaking tank module for its oil weathering software, ADIOS2. Because the present version of the model is not designed for heavy oils, NOAA/HAZMAT is undertaking a series of model-scale tests using releases of canola oil and Orimulsion®. These tests are an extension of leaking tank experiments done earlier for NOAA and for the U. S. Coast Guard, and are part of a joint research program by NOAA/HAZMAT and the U.S. Coast Guard Research and Development Center on the behavior of heavy oil products. This paper describes these tests and their possible application to new spill release models.
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Hubbert, John C., James W. Wilson, Tammy M. Weckwerth, Scott M. Ellis, Mike Dixon, and Eric Loew. "S-Pol’s Polarimetric Data Reveal Detailed Storm Features (and Insect Behavior)." Bulletin of the American Meteorological Society 99, no. 10 (October 2018): 2045–60. http://dx.doi.org/10.1175/bams-d-17-0317.1.
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AbstractThe National Center for Atmospheric Research (NCAR) operates a state-of-the-art S-band dual-polarization Doppler radar (S-Pol) for the National Science Foundation (NSF). This radar has some similar and some distinguishing characteristics to the National Weather Service (NWS) operational Weather Surveillance Radar-1988 Doppler Polarimetric (WSR-88DP). One key difference is that the WSR-88DP is used for operational purposes where rapid 360° volumetric scanning is required to monitor rapid changes in storm characteristics for nowcasting and issuing severe storm warnings. Since S-Pol is used to support the NSF research community, it usually scans at much slower rates than operational radars. This results in higher resolution and higher data quality suitable for many research studies. An important difference between S-Pol and the WSR-88DP is S-Pol’s ability to use customized scan strategies including scanning on vertical surfaces ([range–height indicators (RHIs)], which are presently not done by WSR-88DPs. RHIs provide high-resolution microphysical structures of convective storms, which are central to many research studies. Another important difference is that the WSR-88DP simultaneously transmits horizontal (H) and vertical (V) polarized pulses. In contrast, S-Pol typically transmits alternating H and V pulses, which results in not only higher data quality for research but also allows for the cross-polar signal to be measured. The cross-polar signal provides estimates of the linear depolarization ratio (LDR) and the co- to cross-correlation coefficient that give additional microphysical information. This paper presents plots and interpretations of high-quality, high-resolution polarimetric data that demonstrate the value of S-Pol’s polarimetric measurements for atmospheric research.
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Gao, Yuan, Changlong Guan, Jian Sun, and Lian Xie. "A New Hurricane Wind Direction Retrieval Method for SAR Images without Hurricane Eye." Journal of Atmospheric and Oceanic Technology 35, no. 11 (November 2018): 2229–39. http://dx.doi.org/10.1175/jtech-d-18-0053.1.
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AbstractThis study presents a new approach for hurricane wind direction retrieval utilizing rainband streaks contained in synthetic aperture radar (SAR) images without hurricane eye information, based on the hurricane inflow angle. To calculate the wind direction field, a method for estimating the location of the hurricane center is given. In this paper, four Sentinel-1A (S-1A) images with a hurricane eye are used to clarify the center estimation method. Three S-1A SAR images without a hurricane eye are studied to evaluate the accuracy of the new method. The estimated locations of hurricane centers show good agreement with hurricane track data provided by the National Oceanic and Atmospheric Administration (NOAA)’s Atlantic Oceanographic and Meteorological Laboratory (AOML) Hurricane Research Division (HRD), HurricaneCity, and the National Institute of Informatics (NII). To validate the estimated wind directions, the NOAA HRD dropwindsonde observations for Tropical Storm Karl are collected and compared. The wind directions retrieved by our approach are more consistent with visual inspection than the fast Fourier transform (FFT) method in subimages. Moreover, the retrieved wind speeds utilizing C-band model 5.N (CMOD5.N) are compared with wind speed estimations observed by Stepped Frequency Microwave Radiometer (SFMR). The results suggest that the proposed method has good potential to retrieve hurricane wind direction from SAR images without a hurricane eye and external data.
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Chandrasekar, V., S. Lim, and E. Gorgucci. "Simulation of X-Band Rainfall Observations from S-Band Radar Data." Journal of Atmospheric and Oceanic Technology 23, no. 9 (September 1, 2006): 1195–205. http://dx.doi.org/10.1175/jtech1909.1.
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Abstract To design X-band radar systems as well as evaluate algorithm development, it is useful to have simultaneous X-band observation with and without the impact of path attenuation. One way to develop that dataset is through theoretical models. This paper presents a methodology to generate realistic range profiles of radar variables at attenuating frequencies, such as X band, for rain medium. Fundamental microphysical properties of precipitation, namely, size and shape distribution information, are used to generate realistic profiles of X band starting with S-band observation. Conditioning the simulation from S band maintains the natural distribution of rainfall microphysical parameters. Data from the Colorado State University’s University of Chicago–Illinois State Water Survey (CHILL) radar and the National Center for Atmospheric Research S-band dual-polarization Doppler radar (S-POL) are used to simulate X-band radar variables. Three procedures to simulate the radar variables and sample applications are presented.
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Dymond, John H. "Preface." Pure and Applied Chemistry 79, no. 8 (January 1, 2007): iv. http://dx.doi.org/10.1351/pac20077908iv.
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The 19th International Conference on Chemical Thermodynamics (ICCT-19) took place as part of THERMO International 2006, together with the 16th Symposium on Thermophysical Properties and the 61st Calorimetry Conference, from 30 July to 4 August 2006 at the University of Colorado, Boulder, CO, USA. Dr. W. M. Haynes was President of the Executive Board of THERMO International 2006, and Drs. M. Frenkel, R. D. Chirico, and J. W. Magee were the organizers of ICCT. Overall, 768 speakers submitted the abstracts of their presentations, including about 30 students and 11 exhibitors, from 62 countries (235 from North America, 341 from Europe, 76 from Japan, and 33 from China). About 65 % of the participants were from academia and 15 % from industry, with 20 % from governmental and international organizations.These individual conferences have an overlap of areas of interest, but this was the first time that they have been held jointly at the same site. This provided a unique opportunity for researchers and practitioners worldwide to meet and discuss a broad range of scientific problems in the fields of thermodynamics and thermophysical properties for a wide variety of systems, with applications in chemistry and other scientific and engineering disciplines.After the official opening ceremony, there was an invited keynote presentation by Prof. W. A. Wakeham from the University of Southampton, Southampton, UK, entitled "Thermophysical property measurements: The journey from accuracy to fitness for purpose". The Rossini Award lecture was given by Prof. A. Navrotsky on "Calorimetry of nanoparticles, surfaces, interfaces, thin films, and multilayers".The ICCT program consisted of nine symposia, some of which were held jointly with the other conferences. The plenary lecturers and invited speakers in these symposia, and the titles of the plenary lectures, were as follows:Electrolyte and Non-Electrolyte Solution Thermodynamics: J. M. Prausnitz (plenary), "Some promising frontiers in the thermodynamics of protein solutions"; C. G. Panayiotou, P. R. Tremaine, and T. Kimura (invited)Ionic Liquids: K. Seddon (plenary); "The mark of an educated mind"; L. P. N. Rebelo and C. J. Peters (invited)Molecular Modelling, Including Simulation: D. Evans (plenary), "The fluctuation and non-equilibrium free energy theorems: Theory and experiment"; H. Tanaka, J. Errington, and A. Klamt (invited)Thermochemistry and Molecular Energetics: J. A. de Sousa Martinho Simões (plenary), "Energetics of free radicals: Bridges between gas-phase and solution data"; W. E. Acree, Jr. and J. S. Chickos (invited)Thermodynamics and Properties in the Biological, Medical, Pharmaceutical, Agricultural, and Food Sectors: P. L. Privalov (plenary), "Thermodynamic problems in structural molecular biology"; J. M. Sanchez-Ruiz and H. H. Klump (invited)Databases, Data Systems, Software Applications, and Correlations: M. Satyro (plenary), "Life, data and everything"; R. L. Rowley and R. Sass (invited)Phase Equilibrium, Supercritical Fluids, and Separation Technologies: S. Sandler (plenary), "Computational quantum mechanics: An under-utilized tool for applied thermodynamics"; L. F. Vega and R. P. Danner (invited)Colloid and Interface Science: L. Piculell (plenary), "Controlling structure in associating polymer-surfactant mixtures"; H. K. Yan and K. Lohner (invited)New Materials: V. K. Pecharsky (plenary), "Structure, mechanism, and thermodynamics of novel rare-earth-based inter-metallic materials"; C. Staudt-Bickel and J. Pons (invited)The plenary lectures, with the exception of the lecture by Prof. K. Seddon, are published in this issue.There were workshops on New Experimental Techniques, with Profs. C. Schick and J. P. M. Trusler as invited speakers, on Properties and Processes for a Hydrogen-Based Economy, where Prof. C. J. Peters was the invited speaker, and on Thermodynamic Frontiers and Education, with Profs. R. N. Lichtenthaler and R. Battino as invited speakers.In addition, there was a workshop on the Thermodynamic Properties of Hydration (with Prof. V. Majer as invited speaker), software demonstrations, and two afternoon poster sessions, with over 400 posters. The sessions were held in the well-appointed Stadium Club, against the beautiful backdrop of the Flatirons to the west and the plains stretching across to the east. IUPAC had donated three poster prizes, a framed certificate signed by IUPAC President Brian Henry, a copy of the IUPAC "Gold Book" and a two-year subscription to Chemistry International. These were awarded to Martinez-Herrera Melchor (Mexico), Lisa Ott (USA), and Isabel Marrucho (Spain).Doctorate awards were presented by the International Association of Chemical Thermodynamics (IACT), with sponsorship from Elsevier. The four recipients were M. Fulem (Prague, Czech Republic), Y. U. Paulechka (Minsk, Belarus), E. Asabina (Nizhni Novgorod, Russian Federation), and J. Xu (Trondheim, Norway). They each received a certificate, plus a cash prize of $500, and presented their papers at the conference.All the lectures demonstrated how chemical thermodynamics is making, and will continue to make, very significant contributions to the rapidly developing interdisciplinary fields such as the life sciences, new materials, medicine and pharmacy, new energy resources, the environment, separation technologies, agriculture, green chemistry, and so on. These are all extremely important issues for scientists worldwide, and particularly for those who are in developing or economically disadvantaged countries. The opportunity for face-to-face discussion and communication with scientists from developed countries was a great benefit, which will lead to further research and improved education.The weather was most pleasant for the conference. This, together with the attractive setting of the campus, the welcoming reception, the conference banquet at the National Center for Atmospheric Research, and the high standard of the presentations, made this a memorable conference. In addition, there was a full program of tours for accompanying persons, which included a visit to the mile-high city (Denver). Our thanks are extended to the Conference Chair and Co-chairs, and to all members of the local Organizing Committee, the members of the International Advisory Committee, and the members of the International Scientific Committee. We are most grateful to IUPAC, the International Association of Chemical Thermodynamics, the National Institute of Standards and Technology, the American Society of Mechanical Engineers, and the American Institute of Chemical Engineers, Elsevier, Honeywell, and Mettler Toledo for sponsoring THERMO International 2006.Thermodynamics will continue to be an important area of research for many years to come, with a wide range of applications from chemical engineering to the biosciences. We look forward to the presentation and discussion of the results of further advances in chemical thermodynamics at the next ICCT, which will take place in Warsaw, Poland in August 2008.John H. DymondConference Editor
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Foken, Thomas, and Steven Oncley. "Workshop on Instrumental and Methodical Problems of Land Surface Flux Measurements." Bulletin of the American Meteorological Society 76, no. 7 (July 1, 1995): 1191–224. http://dx.doi.org/10.1175/1520-0477-76.7.1191.
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This report summarizes presentations and discussions that occurred at a workshop held in conjunction with the XIXth General Assembly of the European Geophysical Society (EGS) from 22 to 24 April 1994. The purpose of this workshop was to define the state of the art of micrometeorological flux measurements, to identify problem areas, and to define any additional data that must be taken to solve these problems. This workshop was organized in response to a proposal made at the 1993 EGS conference by T. Foken, T. Delany (National Center for Atmospheric Research), S. Oncley, and L. Tsvang (Institute of Atmospheric Physics, Russia) for a new experiment to investigate the problem of the “unclosed” energy balance. Sixty-one scientists from 14 countries participated in the workshop.
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Smith, William L., Christy Hansen, Anthony Bucholtz, Bruce E. Anderson, Matthew Beckley, Joseph G. Corbett, Richard I. Cullather, et al. "Arctic Radiation-IceBridge Sea and Ice Experiment: The Arctic Radiant Energy System during the Critical Seasonal Ice Transition." Bulletin of the American Meteorological Society 98, no. 7 (July 1, 2017): 1399–426. http://dx.doi.org/10.1175/bams-d-14-00277.1.
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Abstract The National Aeronautics and Space Administration (NASA)’s Arctic Radiation-IceBridge Sea and Ice Experiment (ARISE) acquired unique aircraft data on atmospheric radiation and sea ice properties during the critical late summer to autumn sea ice minimum and commencement of refreezing. The C-130 aircraft flew 15 missions over the Beaufort Sea between 4 and 24 September 2014. ARISE deployed a shortwave and longwave broadband radiometer (BBR) system from the Naval Research Laboratory; a Solar Spectral Flux Radiometer (SSFR) from the University of Colorado Boulder; the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) from the NASA Ames Research Center; cloud microprobes from the NASA Langley Research Center; and the Land, Vegetation and Ice Sensor (LVIS) laser altimeter system from the NASA Goddard Space Flight Center. These instruments sampled the radiant energy exchange between clouds and a variety of sea ice scenarios, including prior to and after refreezing began. The most critical and unique aspect of ARISE mission planning was to coordinate the flight tracks with NASA Cloud and the Earth’s Radiant Energy System (CERES) satellite sensor observations in such a way that satellite sensor angular dependence models and derived top-of-atmosphere fluxes could be validated against the aircraft data over large gridbox domains of order 100–200 km. This was accomplished over open ocean, over the marginal ice zone (MIZ), and over a region of heavy sea ice concentration, in cloudy and clear skies. ARISE data will be valuable to the community for providing better interpretation of satellite energy budget measurements in the Arctic and for process studies involving ice–cloud–atmosphere energy exchange during the sea ice transition period.
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Tobisu, Mamoru, Naoto Chatani, and Victor Snieckus. "Cluster Preface: C–O And Related Bond Activation." Synlett 28, no. 19 (November 20, 2017): 2559–60. http://dx.doi.org/10.1055/s-0036-1592031.
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Mamoru Tobisu received his PhD from Osaka University under the direction of Prof. Shinji Murai (2001). During his PhD studies, he was a visiting scientist (1999) with Prof. Gregory C. Fu at MIT. Following a period as a scientist at the Takeda Pharmaceutical Company (2001–2005), he started his academic career at Osaka University in 2005 as an assistant professor with Prof. Naoto Chatani. He was then appointed as an associate professor at the Center for Atomic and Molecular Technologies at Osaka University (2011) and was promoted to full professor at the Department of Applied Chemistry of Osaka University (2017). He received the Thieme Chemistry Journals Award (2008), the Chemical Society of Japan Award for Young Chemists (2009), the Young Scientists’ Award, a Commendation for Science and Technology from the Minister of Education, Culture, Sports, Science and Technology (2012), the Merck-Banyu Lectureship Award (2012), Thomson Reuters Research Front Award (2016), and the Mukaiyama Award (2018). Naoto Chatani received his PhD in 1984 under Professors Noboru Sonoda and Shinji Murai. In 1984, he joined the Institute of Scientific and Industrial Research at Osaka University as an Assistant Professor in the laboratory of Professor Terukiyo Hanafusa. After postdoctoral studies (1988–1989 under Professor Scott E. Denmark at the University of Illinois, Urbana-Champaign), he moved back to Osaka University and was promoted to the rank of Associate Professor (1992) and to Full Professor (2003). He is a recipient of The Chemical Society of Japan Award for Young Chemists (1990), The Green & Sustainable Chemistry Award from the Minister of Education, Culture, Sports, Science and Technology (2005), the Nagoya Silver Medal (2013), The Chemical Society of Japan Award (2017), a Humboldt Research Award (2017), a Clarivate Analytics Highly Cited Researcher (2017) and will be a recipient of an Arthur C. Cope Scholar Award (2018). Victor Snieckus was born in Kaunas, Lithuania and spent his childhood in Germany during World War II. He received training at U. Alberta, Canada, (B.Sc.), U. California, Berkeley (M.Sc. D.S. Noyce), and U. Oregon (Ph.D. Virgil Boekelheide). He returned to his adopted country for postdoctoral studies (National Research Council, Ottawa, Ted Edwards). Appointments: U. of Waterloo, Assistant (1966) to Professor (1979); Monsanto/NRC Industrial Research Chair, 1992–1998; Queen’s University, Inaugural Bader Chair in Organic Chemistry (1998–2009); Bader Chair Emeritus and Director, Snieckus Innovations, 2009-. Selective awards: A.C. Cope Scholar (2001, one of 5 Canadians), Order of the Grand Duke Gediminas (2002, from the President of Lithuania), Arvedson-Schlenk (2003, Gesellschaft Deutscher Chemiker), Bernard Belleau (2005, Canadian Society for Chemistry), Givaudan-Karrer Medal (2008, U. Zurich), Honoris causa (2009, Technical U. Tallinn, Estonia), Global Lithuanian Award (2012), Yoshida Lectureship (2017). He hopes that he has only temporarily discontinued playing hockey and wishes also to return to the clarinet.
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Hamill, Thomas M., Jeffrey S. Whitaker, Michael Fiorino, and Stanley G. Benjamin. "Global Ensemble Predictions of 2009’s Tropical Cyclones Initialized with an Ensemble Kalman Filter." Monthly Weather Review 139, no. 2 (February 1, 2011): 668–88. http://dx.doi.org/10.1175/2010mwr3456.1.
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Abstract Verification was performed on ensemble forecasts of 2009 Northern Hemisphere summer tropical cyclones (TCs) from two experimental global numerical weather prediction ensemble prediction systems (EPSs). The first model was a high-resolution version (T382L64) of the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS). The second model was a 30-km version of the experimental NOAA/Earth System Research Laboratory’s Flow-following finite-volume Icosahedral Model (FIM). Both models were initialized with the first 20 members of a 60-member ensemble Kalman filter (EnKF) using the T382L64 GFS. The GFS–EnKF assimilated the full observational data stream that was normally assimilated into the NCEP operational Global Statistical Interpolation (GSI) data assimilation, plus human-synthesized “observations” of tropical cyclone central pressure and position produced at the National Hurricane Center and the Joint Typhoon Warning Center. The forecasts from the two experimental ensembles were compared against four operational EPSs from the European Centre for Medium-Range Weather Forecasts (ECMWF), NCEP, the Canadian Meteorological Centre (CMC), and the Met Office (UKMO). The errors of GFS–EnKF ensemble track forecasts were competitive with those from the ECMWF ensemble system, and the overall spread of the ensemble tracks was consistent in magnitude with the track error. Both experimental EPSs had much lower errors than the operational NCEP, UKMO, and CMC EPSs, but the FIM–EnKF tracks were somewhat less accurate than the GFS–EnKF. The ensemble forecasts were often stretched in particular directions, and not necessarily along or across track. The better-performing EPSs provided useful information on potential track error anisotropy. While the GFS–EnKF initialized relatively deep vortices by assimilating the TC central pressure estimate, the model storms filled during the subsequent 24 h. Other forecast models also systematically underestimated TC intensity (e.g., maximum forecast surface wind speed). The higher-resolution models generally had less bias. Analyses were conducted to try to understand whether the additional central pressure observation, the EnKF, or the extra resolution was most responsible for the decrease in track error of the experimental Global Ensemble Forecast System (GEFS)–EnKF over the operational NCEP. The assimilation of the additional TC observations produced only a small change in deterministic track forecasts initialized with the GSI. The T382L64 GFS–EnKF ensemble was used to initialize a T126L28 ensemble forecast to facilitate a comparison with the operational NCEP system. The T126L28 GFS–EnKF EPS track forecasts were dramatically better than the NCEP operational, suggesting the positive impact of the EnKF, perhaps through improved steering flow.
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Hubbert, J. C., S. M. Ellis, W. Y. Chang, and Y. C. Liou. "X-Band Polarimetric Observations of Cross Coupling in the Ice Phase of Convective Storms in Taiwan." Journal of Applied Meteorology and Climatology 53, no. 6 (June 2014): 1678–95. http://dx.doi.org/10.1175/jamc-d-13-0360.1.
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AbstractIn this paper, experimental X-band polarimetric radar data from simultaneous transmission of horizontal (H) and vertical (V) polarizations (SHV) are shown, modeled, and microphysically interpreted. Both range–height indicator data and vertical-pointing X-band data from the Taiwan Experimental Atmospheric Mobile-Radar (TEAM-R) are presented. Some of the given X-band data are biased, which is very likely caused by cross coupling of the H and V transmitted waves as a result of aligned, canted ice crystals. Modeled SHV data are used to explain the observed polarimetric signatures. Coincident data from the National Center for Atmospheric Research S-band polarimetric radar (S-Pol) are presented to augment and support the X-band polarimetric observations and interpretations. The polarimetric S-Pol data are obtained via fast-alternating transmission of horizontal and vertical polarizations (FHV), and thus the S-band data are not contaminated by the cross coupling (except the linear depolarization ratio LDR) observed in the X-band data. The radar data reveal that there are regions in the ice phase where electric fields are apparently aligning ice crystals near vertically and thus causing negative specific differential phase Kdp. The vertical-pointing data also indicate the presence of preferentially aligned ice crystals that cause differential reflectivity Zdr and differential phase ϕdp to be strong functions of azimuth angle.
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Rosenow, Andrew A., David M. Plummer, Robert M. Rauber, Greg M. McFarquhar, Brian F. Jewett, and David Leon. "Vertical Velocity and Physical Structure of Generating Cells and Convection in the Comma Head Region of Continental Winter Cyclones." Journal of the Atmospheric Sciences 71, no. 5 (April 28, 2014): 1538–58. http://dx.doi.org/10.1175/jas-d-13-0249.1.
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Abstract The vertical motion and physical structure of elevated convection and generating cells within the comma heads of three continental winter cyclones are investigated using the Wyoming W-band cloud radar mounted on the National Science Foundation/National Center for Atmospheric Research (NSF/NCAR) C-130, supplemented by analyses from the Rapid Update Cycle model and Weather Surveillance Radar-1988 Doppler (WSR-88D) data. The cyclones followed three distinct archetypical tracks and were typical of those producing winter weather in the midwestern United States. In two of the cyclones, dry air in the middle and upper troposphere behind the Pacific cold front intruded over moist Gulf of Mexico air at lower altitudes within the comma head, separating the comma head into two zones. Elevated convection in the southern zone extended from the cold-frontal surface to the tropopause. The stronger convective updrafts ranged from 2 to 7 m s−1 and downdrafts ranged from −2 to −6 m s−1. The horizontal scale of the convective cells was approximately 5 km. The poleward zone of the comma head was characterized by deep stratiform clouds topped by cloud-top generating cells that reached the tropopause. Updrafts and downdrafts within the generating cells ranged from 1 to 2 m s−1, with the horizontal scale of the cells from about 1 to 2 km. Precipitation on the poleward side of the comma head conformed to a seeder–feeder process—the generating cells seeding the stratiform cloud—which was forced by synoptic-scale ascent. In one case, shallow clouds behind the cyclone’s cold front were also topped by cloud-top generating cells, with vertical motions ranging from 1 to 2 m s−1.
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Dobson, Jerome E. “Jerry.” "Geography's Second Twilight." International Journal of Applied Geospatial Research 8, no. 1 (January 2017): 1–18. http://dx.doi.org/10.4018/ijagr.2017010101.
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Jerome E. Dobson, professor emeritus, University of Kansas; president of the American Geographical Society; and recipient of the 2014 James R. Anderson Medal of Honor in Applied Geography, discusses his career in the context of America's academic purge of geography. Highlights include his time as a Jefferson Science Fellow with the National Academies and U. S. Department of State. Dobson has been recognized with two lifetime achievement awards for his pioneering work in geographic information systems (GIS) and as Alumnus of 2013 at Reinhardt University. His contributions include the paradigm of automated geography, his instrumental role in originating the National Center for Geographic Information and Analysis, and his leadership of the LandScan Global Population Database, the de facto world standard for estimating populations at risk. His recent research includes testing a new system for mapping minefields; designing and promulgating the current world standard for cartographic representation of landmines, minefields, and mine actions; and leading six AGS Bowman Expeditions.
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Montoya, R. D., and A. F. Osorio. "Methodology to Correct Wind Speed during Average Wind Conditions: Application to the Caribbean Sea." Journal of Atmospheric and Oceanic Technology 31, no. 9 (September 1, 2014): 1922–45. http://dx.doi.org/10.1175/jtech-d-13-00124.1.
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Abstract The spatial and temporal variability of ocean wind waves plays an important role in many engineering and environmental problems. Although research in this area has been improved in recent decades thanks to the emergence of satellite data, in many cases this information does not have the appropriate resolution for more detailed and local research. In view of this, reanalysis data developed by several meteorological agencies have appeared as a good alternative to force the most popular ocean wind-wave models. Thus, to achieve more accuracy in the data, the 60-yr Global Atmospheric Reanalysis 1 carried out by the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) has been corrected, employing the vector correlation and triple collocation theories combined with information from different accurate sources. The comparison of wind speed with satellite and in situ buoy data before correction reveals an important underestimation for areas near the Colombian coast. The wind speed root-mean-square error (RMSE) between corrected data and satellite measurements at locations near the Colombian Caribbean coast without calibration is 3.8 m s−1, while for corrected data it is 2.0 m s−1, showing a decrease in the RMSE of almost 47%. For significant wave height for buoy 41194 (Barranquilla, Colombia), the RMSE between the modeled data and measurements without correction is 0.99 m, while for the corrected data it is 0.40 m, showing a decrease in the RMSE of almost 55%. The results obtained clearly show an increase in the accuracy of the calibrated wind speed.
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Rauber, Robert M., Scott M. Ellis, J. Vivekanandan, Jeffrey Stith, Wen-Chau Lee, Greg M. McFarquhar, Brian F. Jewett, and Andrew Janiszeski. "Finescale Structure of a Snowstorm over the Northeastern United States: A First Look at High-Resolution HIAPER Cloud Radar Observations." Bulletin of the American Meteorological Society 98, no. 2 (February 1, 2017): 253–69. http://dx.doi.org/10.1175/bams-d-15-00180.1.
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Abstract The newly developed High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) is an airborne, W-band, dual-polarization, Doppler research radar that fits within an underwing pod on the National Center for Atmospheric Research Gulfstream-V HIAPER aircraft. On 2 February 2015, the HCR was flown on its maiden research voyage over a cyclone along the Northeast coast of the United States. Six straight flight legs were flown over 6 h between the northern tip of Delaware Bay and Bangor, Maine, crossing the rain–snow line, and passing directly over Boston, Massachusetts, which received over 16 in. of snow during the event. The HCR, which recorded reflectivity, radial velocity, spectral width, and linear depolarization ratio with a 0.7° beam, was pointed at nadir from a flight altitude of 12,800 m (42,000 ft). The along-track resolution ranged between 20 and 200 m, depending on range, at aircraft speeds varying between 200 and 275 m s−1. The range resolution was 19.2 m. Remarkably detailed finescale structures were found throughout the storm system, including cloud-top generating cells, upright elevated convection, layers of turbulence, vertical velocity perturbations across the melting level, gravity waves, boundary layer circulations, and other complex features. Vertical velocities in these features ranged from 1 to 5 m s−1, and many features were on scales of 5 km or less. The purpose of this paper is to introduce the HCR and highlight the remarkable finescale structures revealed within this Northeast U.S. cyclone by the HCR.
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Splitt, Michael E., Jaclyn A. Shafer, Steven M. Lazarus, and William P. Roeder. "Evaluation of the National Hurricane Center’s Tropical Cyclone Wind Speed Probability Forecast Product." Weather and Forecasting 25, no. 2 (April 1, 2010): 511–25. http://dx.doi.org/10.1175/2009waf2222279.1.
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Abstract A tropical cyclone (TC) wind speed probability forecast product developed at the Cooperative Institute for Research in the Atmosphere (CIRA) and adopted by the National Hurricane Center (NHC) is evaluated for U.S. land-threatening and landfalling events over four hurricane seasons from 2004 to 2007. A key element of this work is the discernment of risk associated with the interval forecast probabilities for the three wind speed categories (i.e., 34, 50, and 64 kt, where 1 kt = 0.52 m s−1). A quantitative assessment of the interval probabilities (0–12, 12–24, 24–36, 36–48, 48–72, 72–96, and 96–120 h) is conducted by converting them into binary (yes–no) forecasts using decision thresholds that are selected using the true skill statistic (TSS) and the Heidke skill score (HSS). The NHC product performs well as both the HSS and TSS demonstrate skill out to the 48–72- and 72–120-h intervals, respectively. Overall, reliability diagrams and bias scores indicate that the NHC product has a tendency to overforecast event likelihood for cases where the forecast probabilities exceed 60%. Specifically, the NHC product tends to overforecast for the 34-kt category but underforecasts for the 64-kt category, especially at later forecast intervals. Results for the 50-kt category are mixed but also exhibit a tendency to underforecast during the latter intervals. Decision thresholds range from 1% to 55% depending on the selection method, wind speed category, and time interval. Given that the average forecast probabilities decrease with forecast hour, small forecast probabilities may be meaningful. The HSS is recommended over the TSS for decision threshold selection because the use of the TSS introduces significant bias and the HSS is less sensitive to filtering of correct negatives.
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Yang, Jungang, and Jie Zhang. "Comparison of Oceansat-2 Scatterometer Wind Data with Global Moored Buoys and ASCAT Observation." Advances in Meteorology 2019 (March 19, 2019): 1–9. http://dx.doi.org/10.1155/2019/1651267.
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The Oceansat-2 satellite was launched on 23 September 2009 by the Indian Space Research Organization (ISRO). In this study, the historic archived OSCAT wind vectors are compared with the global moored buoys’ wind observations, including the U.S. National Data Buoy Center (NDBC), the Tropical Atmosphere Ocean (TAO), the Pilot Research Moored Array in the Tropical Atlantic (PIRATA), the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA), and Advanced Scatterometer (ASCAT) wind data in the same period of OSCAT by calculating the statistical parameters, namely, the root mean square error (RMSE), bias (mean of residuals), and correlation coefficient (R) between the collocated data. The comparisons with the global moored buoys show that the OSCAT wind vectors are consistent with buoys’ wind measurements. The average errors of the OSCAT wind vectors are 1.20 m/s and 17.7°. The analysis of the OSCAT wind vector errors at different buoy wind speeds in bins of 1 m/s indicates that the accuracy of the OSCAT wind speed first increases and then decreases with the increasing wind speed. The comparisons of OSCAT wind vectors and ASCAT wind vectors show that the average RMSEs of their differences are 1.27 m/s and 20.17°. In general, the accuracies of the OSCAT wind vectors satisfy the general scatterometer’s mission requirement and are consistent with ASCAT wind data. OSCAT wind vectors can be used in the global change study by the combination with other scatterometer data.
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Nakatani, Y., T. Komatsu, U. Shimizu-kaya, T. Itioka, T. Itino, R. Hashim, S. Ueda, W. Asfiya, H. Herwina, and S. Hartini. "Additional species and records of the “horn-backed” Pilophorus plant bugs in Southeast Asia (Heteroptera: Miridae: Phylinae)." Tijdschrift voor Entomologie 159, no. 1 (April 21, 2016): 1–8. http://dx.doi.org/10.1163/22119434-15812050.
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Three new species of the “horn-backed” phyline plant bug genus Pilophorus Hahn, namely, P. erinaceulus, P. maruyamai and P. parvolus, are described from Borneo, Malaysia and Sumatra, Indonesia. The following species are newly recorded within Southeast Asia: P. lambirensis from the Malay Peninsula; P. laticollaris from Sumatra; P. longirostris and P. multivillus from Borneo. A supplementary key to the key by Nakatani et al. (2013) is provided. Y. Nakatani*, Natural Resources Inventory Center, National Institute for Agro-Environmental Sciences, Kannondai, 3-1-3, Tsukuba, Ibaraki, 305-8604, Japan. nakatany@affrc.go.jp T. Komatsu, Institute of Tropical Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan. corocoro1232000@yahoo.co.jp U. Shimizu-kaya, Center for Ecological Research, Kyoto University, Hirano, Otsu, Shiga 520-2113, Japan. shimizu.kaya.55c@st.kyoto-u.ac.jp T. Itioka, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan. ichioka.takao.5m@kyoto-u.ac.jp T. Itino, S. Ueda, Department of Biology, Faculty of Science, Shinshu University 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan. ueda32@shinshu-u.ac.jp R. Hashim, Institute of Biological Science, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. rh4758@gmail.com W. Asfiya, S. Hartini, Division of Zoology, Research Center for Biology, Indonesian Institute of Sciences, Jl. Raya Jakarta-Bogor Km. 46, Cibinong, Bogor, 16911, Indonesia. wara.asfiya@lipi.go.id H. Herwina, Laboratorium Riset Taksonomi Hewan, Jurusan Biologi, Fakultas Matematika dan Ilmu Pengetahuan Alam, Universitas Andalas, Kampus UNAND Limau Manis, Padang, 25163, Indonesia. hennyf91@gmail.com
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Hubbert, J. C. "Differential Reflectivity Calibration and Antenna Temperature." Journal of Atmospheric and Oceanic Technology 34, no. 9 (September 2017): 1885–906. http://dx.doi.org/10.1175/jtech-d-16-0218.1.
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AbstractTemporal differential reflectivity bias variations are investigated using the National Center for Atmospheric Research (NCAR) S-band dual-polarization Doppler radar (S-Pol). Using data from the Multi-Angle Snowflake Camera-Ready (MASCRAD) Experiment, S-Pol measurements over extended periods reveal a significant correlation between the ambient temperature at the radar site and the bias. Using radar scans of the sun and the ratio of cross-polar powers, the components of the radar that cause the variation of the bias are identified. It is postulated that the thermal expansion of the antenna is likely the primary cause of the observed bias variation. The cross-polar power (CP) calibration technique, which is based on the solar and cross-polar power measurements, is applied to data from the Plains Elevated Convection at Night (PECAN) field project. The bias from the CP technique is compared to vertical-pointing bias measurements, and the uncertainty of the bias estimates is given. An algorithm is derived to correct the radar data for the time- and temperature-varying bias. Bragg scatter measurements are used to corroborate the CP technique bias measurements.
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Hubbert, J. C., S. M. Ellis, M. Dixon, and G. Meymaris. "Modeling, Error Analysis, and Evaluation of Dual-Polarization Variables Obtained from Simultaneous Horizontal and Vertical Polarization Transmit Radar. Part I: Modeling and Antenna Errors." Journal of Atmospheric and Oceanic Technology 27, no. 10 (October 1, 2010): 1583–98. http://dx.doi.org/10.1175/2010jtecha1336.1.
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Abstract In this two-part paper the biases of polarimetric variables from simultaneous horizontally and vertically transmitted (SHV) data are investigated. Here, in Part I, a radar-scattering model is developed and antenna polarization errors are investigated and estimated. In Part II, experimental data from the National Center for Atmospheric Research S-band dual-polarization Doppler radar (S-Pol) and the National Severe Storms Laboratory polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) radar, KOUN, are used to illustrate biases in differential reflectivity (Zdr). The biases in the SHV polarimetric variables are caused by cross coupling of the horizontally (H) and vertically (V) polarized signals. The cross coupling is caused by the following two primary sources: 1) the nonzero mean canting angle of the propagation medium and 2) antenna polarization errors. The biases are strong functions of the differential propagation phase (ϕdp) and the phase difference between the H and V transmitted field components. The radar-scattering model developed here allows for the evaluation of biases caused by cross coupling as a function of ϕdp, with the transmission phase difference as a parameter. Also, antenna polarization errors are estimated using solar scan measurements in combination with estimates of the radar system’s linear depolarization ratio (LDR) measurement limit. Plots are given that show expected biases in SHV Zdr for various values of the LDR system’s limit.
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Chaney, Nathaniel W., Justin Sheffield, Gabriele Villarini, and Eric F. Wood. "Development of a High-Resolution Gridded Daily Meteorological Dataset over Sub-Saharan Africa: Spatial Analysis of Trends in Climate Extremes." Journal of Climate 27, no. 15 (July 29, 2014): 5815–35. http://dx.doi.org/10.1175/jcli-d-13-00423.1.
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Abstract Assessing changes in the frequency and intensity of extreme meteorological events and their impact on water resources, agriculture, and infrastructure is necessary to adequately prepare and adapt to future change. This is a challenge in data-sparse regions such as sub-Saharan Africa, where a lack of high-density and temporally consistent long-term in situ measurements complicates the analysis. To address this, a temporally homogenous and high-temporal- and high-spatial-resolution meteorological dataset is developed over sub-Saharan Africa (5°S–25°N), covering the time period between 1979 and 2005. It is developed by spatially downscaling the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis to a 0.1° spatial resolution, detecting and correcting for temporal inhomogeneities, and by removing random errors and biases by assimilating quality-controlled and gap-filled Global Summary of the Day (GSOD) in situ measurements. The dataset is then used to determine the statistical significance and magnitude of changes in climate extremes between 1979 and 2005. The results suggest a shift in the distribution of daily maximum and minimum temperatures toward a warmer mean with a faster increase in warm than cold events. Changes in the mean annual precipitation and heavy rainfall events are significant only in regions affected by the Sahel droughts of the 1970s and 1980s.
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Prado, Luciana Figueiredo, and Ilana Wainer. "PLANETARY-SCALE CLIMATIC INDICES AND RELATIONSHIP BETWEEN DECADAL VARIABILITY OF RAINFALL IN NORTHEASTERN AND SOUTHERN BRAZIL." Revista Brasileira de Geofísica 31, no. 1 (March 1, 2013): 31. http://dx.doi.org/10.22564/rbgf.v31i1.244.
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This work analyzes the relationship between climatic index and rainfall in the Northeastern (NE) and Southern (S) Brazil, in decadal timescale. The climatic indices were obtained from the reanalysis data from NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) between 1948 and 2008. Subsequently, (indices and rainfall correlation coefficients derived from the GPCP (Global Precipitation Climatology Project) dataset were calculated using filtered and non-filtered time series, within the decadal frequency). The results show that ElNi ˜no Southern Oscillation (ENSO) is the main phenomenon influencing NE rainfall due to related changes in tropical circulation while the Intertropical Convergence Zone (ITCZ) annual cycle also affects rainfall in the NE to a lesser extent. Meanwhile, in the Southern region, the most important phenomenon is the Southern Annular Mode (SAM) which controls cyclones activity in mid-latitudes. The Tropical Atlantic dipole index (ADI) also influences the rainfall in the Southern, and this might be related to moisture being transported from the ocean to the continent, which is then carried to the South by the Low Level Jet. It is also suggested that the decadal variability of the Tropical Atlantic Ocean and its influence on the precipitation in NE andS regions of Brazil are episodic because no significant correlations were obtained at decadal frequency. Finally, the spectral analysis revealed that the interannual timescale is the main frequency of variability in both studied regions, affecting differently each one of them. RESUMO: Este trabalho analisa as relações entre índices climáticos e a precipitação no Nordeste (NE) e Sul (S) do Brasil, em escala decadal. Os índices climáticos foram obtidos a partir de dados da reanálise do NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research), para o período de 1948 a 2008. Posteriormente, foram obtidos os coeficientes de correlação entre os índices e as anomalias de precipitação advindas do banco de dados do GPCP (Global Precipitation Climatology Project) nestas regiões, utilizando séries não filtradas e séries filtradas na frequência decadal. Os resultados sugerem que o principal fenômeno que modula a precipitação no NE é o El Ni˜no-Oscilação Sul (ENOS), devido às alterações na circulação tropical, e também o ciclo anual da Zona de Convergência Intertropical (ZCIT), que modula a estação chuvosa do NE. Na região S, o fenômeno que mais influencia a precipitação em escala decadal é o Modo Anular Sul (SAM),por modular a atividade ciclogenética em latitudes médias, além do índice do dipolo do Atlântico Tropical (DA), que pode estar ligado ao aporte de umidade oceânica para o continente, e levada ao S pelo jato de baixos níveis. Também se sugere que a variabilidade decadal do Atlântico tropical e sua influência na precipitação no NE sejam episódicas, e não periódica, já que não foram obtidas correlações importantes para este índice, na frequência estudada. Finalmente, a análise espectral revelouque a escala interanual é a principal frequência de variabilidade temporal em ambas as regiões, com efeitos diversos em cada uma delas.Palavras-chave: precipitação, ENOS, Atlântico, SAM.
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Friedrich, Katja, and Martin Hagen. "Evaluation of Wind Vectors Measured by a Bistatic Doppler Radar Network." Journal of Atmospheric and Oceanic Technology 21, no. 12 (December 1, 2004): 1840–54. http://dx.doi.org/10.1175/jtech-1679.1.
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Abstract By installing and linking additional receivers to a monostatic Doppler radar, several wind components can be measured and combined into a wind vector field. Such a bistatic Doppler radar network was developed in 1993 by the National Center for Atmospheric Research and has been in operation at different research departments. Since then, the accuracy of wind vectors has been investigated mainly based on theoretical examinations. Observational analysis of the accuracy has been limited to comparisons of dual-Doppler-derived wind vectors always including the monostatic Doppler radar. Intercomparisons to independent wind measurements have not yet been accomplished. In order to become an alternative to monostatic multiple–Doppler applications, the reliability of wind vector fields has to be also proven by observational analysis. In this paper wind vectors measured by a bistatic Doppler radar network are evaluated by 1) internally comparing results of bistatic receivers; 2) comparing with independent wind measurements observed by a second Doppler radar; and 3) comparing with in situ flight measurements achieved with a research aircraft during stratiform precipitation events. Investigations show how reliable bistatically measured wind fields are and how they can contribute highly to research studies, weather surveillance, and forecasting. As a result of the intercomparison, the instrumentation error of the bistatic receivers can be assumed to be within 1 m s−1. Differences between bistatic Doppler radar and independent measurements range mainly between 2 and 3 m s−1.
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CONNOR, P. D. T. O'. "U. S. Military Handbook 338: Electronic Reliability Design Handbook. Available from the U.S. National Technical Information Center, Springfield, Virginia. (In the U.K. from London Information, Index House, Ascot, Berkshire)." Quality and Reliability Engineering International 2, no. 2 (April 1986): 139. http://dx.doi.org/10.1002/qre.4680020217.
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Zhou, Lihang, Murty Divakarla, Xingpin Liu, Arron Layns, and Mitch Goldberg. "An Overview of the Science Performances and Calibration/Validation of Joint Polar Satellite System Operational Products." Remote Sensing 11, no. 6 (March 22, 2019): 698. http://dx.doi.org/10.3390/rs11060698.
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The Suomi National Polar-orbiting Partnership (S-NPP) satellite, launched in October 2011, initiated a series of the next-generation weather satellites for the National Oceanic and Atmospheric Administration (NOAA) Joint Polar Satellite System (JPSS) program. The JPSS program at the Center for Satellite Applications and Research (JSTAR) leads the development of the algorithms, the calibration and validation of the products to meet the specified requirements, and long-term science performance monitoring and maintenance. All of the S-NPP products have been validated and are in successful operation. The recently launched JPSS-1 (renamed as NOAA-20) satellite is producing high-quality data products that have been available from S-NPP, along with additional products, as a direct result of the instrument upgrades and science improvements. This paper presents an overview of the JPSS product suite, the performance metrics achieved for the S-NPP, and the utilization of the products by NOAA stakeholders and user agencies worldwide. The status of NOAA-20 science data products and ongoing calibration/validation (Cal/Val) efforts are discussed for user awareness. In addition, operational implementation statuses of JPSS enterprise (multisensor and multiplatform) science algorithms for product generation and science product reprocessing efforts for the S-NPP mission are discussed.
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Geresdi, István, and Roy Rasmussen. "Freezing Drizzle Formation in Stably Stratified Layer Clouds. Part II: The Role of Giant Nuclei and Aerosol Particle Size Distribution and Solubility." Journal of the Atmospheric Sciences 62, no. 7 (July 1, 2005): 2037–57. http://dx.doi.org/10.1175/jas3452.1.
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Abstract This paper investigates how the characteristics of aerosol particles (size distribution and solubility) as well as the presence of giant nuclei affect drizzle formation in stably stratified layer clouds. A new technique was developed to simulate the evolution of water drops from wet aerosol particles and implemented into a detailed microphysical model. The detailed microphysical model was incorporated into a one-dimensional parcel model and a two-dimensional version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5). Sensitivity experiments were performed with the parcel model using a constant updraft speed and with the two-dimensional model by simulating flow over a bell-shaped mountain. The results showed that 1) stably stratified clouds with weak updrafts (<10 cm s−1) can form drizzle relatively rapidly for maritime size distributions with any aerosol particle solubility, and for continental size distributions with highly insoluble particles due to the low number of activated cloud condensation nuclei (CCN) (<100 cm−3), 2) drizzle is suppressed in stably stratified clouds with weak updrafts (<10 cm s−1) for highly soluble urban and extreme urban size distributions, and 3) the presence of giant nuclei only has an effect on drizzle formation for the highly soluble continental aerosol size distributions.
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Minor, Hilary A., Robert M. Rauber, Sabine Göke, and Larry Di Girolamo. "Trade Wind Cloud Evolution Observed by Polarization Radar: Relationship to Giant Condensation Nuclei Concentrations and Cloud Organization." Journal of the Atmospheric Sciences 68, no. 5 (May 1, 2011): 1075–96. http://dx.doi.org/10.1175/2010jas3675.1.
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Abstract Shallow marine trade wind cumuli are one of the most prevalent cloud types in the tropical atmosphere. Understanding how precipitation forms within these clouds is necessary to advance our knowledge concerning their role in climate. This paper presents a statistical analysis of the characteristic heights and times at which precipitation in trade wind clouds passes through distinct stages in its evolution as defined by the equivalent radar reflectivity factor at horizontal polarization ZH, the differential reflectivity ZDR, and the spatial correlation between and averages of these variables. The data were obtained during the Rain in Cumulus over the Ocean (RICO) field campaign by the National Center for Atmospheric Research (NCAR) S-band dual-polarization (S-Pol) Doppler radar, the National Science Foundation (NSF)–NCAR C130 aircraft, and soundings launched near the radar. The data consisted of 76 trade cumuli that were tracked from early echo development through rainout on six days during RICO. Trade wind clouds used in the statistical analyses were segregated based on giant condensation nuclei (GCN) measurements made during low-level aircraft flight legs on the six days. This study found that the rate of precipitation formation in shallow marine cumulus was unrelated to the GCN concentration in the ambient environment. Instead, the rate at which precipitation developed in the clouds appeared to be related to the mesoscale forcing as suggested by the cloud organization. Although GCN had no influence on the rate of precipitation development, the data suggest that they do contribute to a modification of the rain drop size distribution within the clouds. With very few exceptions, high threshold values of ZDR were found well above cloud base on days with high GCN concentrations. On the days that were exceptions, these threshold values were almost always achieved near cloud base.
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Hubbert, J. C., S. M. Ellis, W. Y. Chang, S. Rutledge, and M. Dixon. "Modeling and Interpretation of S-Band Ice Crystal Depolarization Signatures from Data Obtained by Simultaneously Transmitting Horizontally and Vertically Polarized Fields." Journal of Applied Meteorology and Climatology 53, no. 6 (June 2014): 1659–77. http://dx.doi.org/10.1175/jamc-d-13-0158.1.
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AbstractData collected by the National Center for Atmospheric Research S-band polarimetric radar (S-Pol) during the Terrain-Influenced Monsoon Rainfall Experiment (TiMREX) in Taiwan are analyzed and used to infer storm microphysics in the ice phase of convective storms. Both simultaneous horizontal (H) and vertical (V) (SHV) transmit polarization data and fast-alternating H and V (FHV) transmit polarization data are used in the analysis. The SHV Zdr (differential reflectivity) data show radial stripes of biased data in the ice phase that are likely caused by aligned and canted ice crystals. Similar radial streaks in the linear depolarization ratio (LDR) are presented that are also biased by the same mechanism. Dual-Doppler synthesis and sounding data characterize the storm environment and support the inferences concerning the ice particle types. Small convective cells were observed to have both large positive and large negative Kdp (specific differential phase) values. Negative Kdp regions suggest that ice crystals are vertically aligned by electric fields. Since high |Kdp| values of 0.8° km−1 in both negative and positive Kdp regions in the ice phase are accompanied by Zdr values close to 0 dB, it is inferred that there are two types of ice crystals present: 1) smaller aligned ice crystals that cause the Kdp signatures and 2) larger aggregates or graupel that cause the Zdr signatures. The inferences are supported with simulated ice particle scattering calculations. A radar scattering model is used to explain the anomalous radial streaks in SHV and LDR.
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Wang, Hongli, Xiang-Yu Huang, Juanzhen Sun, Dongmei Xu, Man Zhang, Shuiyong Fan, and Jiqin Zhong. "Inhomogeneous Background Error Modeling for WRF-Var Using the NMC Method." Journal of Applied Meteorology and Climatology 53, no. 10 (October 2014): 2287–309. http://dx.doi.org/10.1175/jamc-d-13-0281.1.
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AbstractBackground error modeling plays a key role in a variational data assimilation system. The National Meteorological Center (NMC) method has been widely used in variational data assimilation systems to generate a forecast error ensemble from which the climatological background error covariance can be modeled. In this paper, the characteristics of the background error modeling via the NMC method are investigated for the variational data assimilation system of the Weather Research and Forecasting (WRF-Var) Model. The background error statistics are extracted from short-term 3-km-resolution forecasts in June, July, and August 2012 over a limited-area domain. It is found 1) that background error variances vary from month to month and also have a feature of diurnal variations in the low-level atmosphere and 2) that u- and υ-wind variances are underestimated and their autocorrelation length scales are overestimated when the default control variable option in WRF-Var is used. A new approach of control variable transform (CVT) is proposed to model the background error statistics based on the NMC method. The new approach is capable of extracting inhomogeneous and anisotropic climatological information from the forecast error ensemble obtained via the NMC method. Single observation assimilation experiments show that the proposed method not only has the merit of incorporating geographically dependent covariance information, but also is able to produce a multivariate analysis. The results from the data assimilaton and forecast study of a real convective case show that the use of the new CVT improves synoptic weather system and precipitation forecasts for up to 12 h.
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Yan, Yuping, Paul A. Mayewski, Shichang Kang, and Eric Meyerson. "An ice-core proxy for Antarctic circumpolar zonal wind intensity." Annals of Glaciology 41 (2005): 121–30. http://dx.doi.org/10.3189/172756405781813294.
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AbstractUsing US National Centers for Environmental Prediction/US National Center for Atmospheric Research re-analysis data, we investigate the relationships between crustal ion (nssCa2+) concentrations from three West Antarctic ice cores, namely, Siple Dome (SD), ITASE00-1 (IT001) and ITASE01-5 (IT015), and primary components of the climate system, namely, air pressure/geopotential height, zonal (u) and meridional (v) wind strength. Linear correlation analyses between nssCa2+ concentrations and both air-pressure and wind fields for the period of overlap between records indicate that the SD nssCa2+ variation is positively correlated with spring circumpolar zonal wind, while IT001 nssCa2+ has a positive correlation with circumpolar zonal wind throughout the year (r > 0.3, p < 0.01). Intensified Southern Westerlies circulation is conducive to transport of more crustal aerosols to both sites. Further correlation analyses between nssCa2+ concentrations from SD and IT001 and atmospheric circulation suggest that the high inland plateau (represented by core IT001) is largely influenced by transport from the upper troposphere. IT015 nssCa2+ is negatively correlated with westerly wind in October and November, suggesting that stronger westerly circulation may weaken the transport of crustal species to IT015. Correlations of nssCa2+ from the three ice cores with the Antarctic Oscillation index are consistent with results developed from the wind-field investigation. In addition, calibration between nssCa2+ concentration and the multivariate El Niño–Southern Oscillation (ENSO) index shows that crustal species transport to IT001 is enhanced during strong ENSO events.
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Bromwich, David H., Biao Chen, Keith M. Hines, and Richard I. Cullather. "Global atmospheric responses to Antarctic forcing." Annals of Glaciology 27 (1998): 521–27. http://dx.doi.org/10.3189/1998aog27-1-521-527.
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To evaluate the greatest impact that sea-ice anomalies around Antarctica could have on the global atmosphere, 15 year seasonal cycle simulations are conducted with the U.S. National Center for Atmospheric Research Community Climate Model version 2.1. Sensitivity simulations are performed with the following conditions: (1) all sea ice in the Southern Hemisphere is replaced by year-round open water, but the permanent ice shelves are retained (NSIS); and (2) all sea ice in the Southern Hemisphere and the major ice shelves are removed and replaced by open water (NISH). The results are compared to a standard run (CNT) with boundary conditions set for the present climate. The comparison shows that trains of positive and negative anomalies in zonal-mean fields extend into the tropical latitudes of the Northern Hemisphere. Anomalies are largest during April-October. The additional removal of the ice shelves in NISH enhances the response, as zonally averaged anomalies are similar in pattern to those in NSIS but are roughly twice as large poleward of 50° S, and only slightly larger farther north. Anomalies in the eddy fields are found in both hemispheres. in NISH, and to a lesser degree in NSIS. these anomalies appear to be related to a delayed northern advance over China during June of the rain front associated with the summer monsoon. Consequently, precipitation is enhanced in middle and southern China and decreased in northern China. Observational analyses have also found links between Antarctic sea-ice variations and modulations of the East Asian monsoon.
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Payne, Clark D., Terry J. Schuur, Donald R. MacGorman, Michael I. Biggerstaff, Kristin M. Kuhlman, and W. David Rust. "Polarimetric and Electrical Characteristics of a Lightning Ring in a Supercell Storm." Monthly Weather Review 138, no. 6 (June 1, 2010): 2405–25. http://dx.doi.org/10.1175/2009mwr3210.1.
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Abstract On 30 May 2004, a supercell storm was sampled by a suite of instrumentation that had been deployed as part of the Thunderstorm Electrification and Lightning Experiment (TELEX). The instrumentation included the Oklahoma Lightning Mapping Array (OK-LMA), the National Severe Storms Laboratory S-band Weather Surveillance Radar-1988 Doppler (WSR-88D) polarimetric radar at Norman, Oklahoma, and two mobile C-band, Shared Mobile Atmospheric Research and Teaching Radars (SMART-R). Combined, datasets collected by these instruments provided a unique opportunity to investigate the possible relationships among the supercell’s kinematic, microphysical, and electrical characteristics. This study focuses on the evolution of a ring of lightning activity that formed near the main updraft at approximately 0012 UTC, matured near 0039 UTC, and collapsed near 0050 UTC. During this time period, an F2-intensity tornado occurred near the lightning-ring region. Lightning density contours computed over 1-km layers are overlaid on polarimetric and dual-Doppler data to assess the low- and midlevel kinematic and microphysical characteristics within the lightning-ring region. Results indicate that the lightning ring begins in the middle and upper levels of the precipitation-cascade region, which is characterized by inferred graupel. The second time period shows that the lightning source densities take on a horizontal u-shaped pattern that is collocated with midlevel differential reflectivity and correlation coefficient rings and with the strong cyclonic vertical vorticity noted in the dual-Doppler data. The final time period shows dissipation of the u-shaped pattern and the polarimetric signatures as well as an increase in the lightning activity at the lower levels associated with the development of the rear-flank downdraft (RFD) and the envelopment of the vertical vorticity maximum by the RFD.
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Lauritzen, Peter Hjort, Mark A. Taylor, James Overfelt, Paul A. Ullrich, Ramachandran D. Nair, Steve Goldhaber, and Rory Kelly. "CAM-SE–CSLAM: Consistent Coupling of a Conservative Semi-Lagrangian Finite-Volume Method with Spectral Element Dynamics." Monthly Weather Review 145, no. 3 (March 2017): 833–55. http://dx.doi.org/10.1175/mwr-d-16-0258.1.
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An algorithm to consistently couple a conservative semi-Lagrangian finite-volume transport scheme with a spectral element (SE) dynamical core is presented. The semi-Lagrangian finite-volume scheme is the Conservative Semi-Lagrangian Multitracer (CSLAM), and the SE dynamical core is the National Center for Atmospheric Research (NCAR)’s Community Atmosphere Model–Spectral Elements (CAM-SE). The primary motivation for coupling CSLAM with CAM-SE is to accelerate tracer transport for multitracer applications. The coupling algorithm result is an inherently mass-conservative, shape-preserving, and consistent (for a constant mixing ratio, the CSLAM solution reduces to the SE solution for air mass) transport that is efficient and accurate. This is achieved by first deriving formulas for diagnosing SE airmass flux through the CSLAM control volume faces. Thereafter, the upstream Lagrangian CSLAM areas are iteratively perturbed to match the diagnosed SE airmass flux, resulting in an equivalent upstream Lagrangian grid that spans the sphere without gaps or overlaps (without using an expensive search algorithm). This new CSLAM algorithm is not specific to airmass fluxes provided by CAM-SE but applies to any airmass fluxes that satisfy the Lipshitz criterion and for which the Courant number is less than one.
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Hoffmann, Lars, Albert Hertzog, Thomas Rößler, Olaf Stein, and Xue Wu. "Intercomparison of meteorological analyses and trajectories in the Antarctic lower stratosphere with Concordiasi superpressure balloon observations." Atmospheric Chemistry and Physics 17, no. 13 (July 4, 2017): 8045–61. http://dx.doi.org/10.5194/acp-17-8045-2017.
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Abstract. In this study we compared temperatures and horizontal winds of meteorological analyses in the Antarctic lower stratosphere, a region of the atmosphere that is of major interest regarding chemistry and dynamics of the polar vortex. The study covers the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis, the ERA-Interim reanalysis, the Modern-Era Retrospective analysis for Research and Applications version 1 and 2 (MERRA and MERRA-2), and the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The comparison was performed with respect to long-duration observations from 19 superpressure balloon flights during the Concordiasi field campaign in September 2010 to January 2011. Most of the balloon measurements were conducted at altitudes of 17–18.5 km and latitudes of 60–85° S. We found that large-scale state temperatures of the analyses have a mean precision of 0.5–1.4 K and a warm bias of 0.4–2.1 K with respect to the balloon data. Zonal and meridional winds have a mean precision of 0.9–2.3 m s−1 and a bias below ±0.5 m s−1. Standard deviations related to small-scale fluctuations due to gravity waves are reproduced at levels of 15–60 % for temperature and 30–60 % for the horizontal winds. Considering the fact that the balloon observations have been assimilated into all analyses, except for NCEP/NCAR, notable differences found here indicate that other observations, the forecast models, and the data assimilation procedures have a significant impact on the analyses as well. We also used the balloon observations to evaluate trajectory calculations with our new Lagrangian transport model Massive-Parallel Trajectory Calculations (MPTRAC), where vertical motions of simulated trajectories were nudged to pressure measurements of the balloons. We found relative horizontal transport deviations of 4–12 % and error growth rates of 60–170 km day−1 for 15-day trajectories. Dispersion simulations revealed some difficulties with the representation of subgrid-scale wind fluctuations in MPTRAC, as the spread of air parcels simulated with different analyses was not consistent. However, although case studies suggest that the accuracy of trajectory calculations is influenced by meteorological complexity, diffusion generally does not contribute significantly to transport deviations in our analysis. Overall, evaluation results are satisfactory and compare well to earlier studies using superpressure balloon observations.
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Cunde, Xiao, Ian Allison, Ren Jiawen, Qin Dahe, Zhang Mingjun, and Li Zhongqin. "Meteorological and glaciological evidence for different climatic variations on the east and west sides of the Lambert Glacier basin, Antarctica." Annals of Glaciology 39 (2004): 188–94. http://dx.doi.org/10.3189/172756404781814492.
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AbstractSurface mass-balance studies and climatic records from firn cores show remarkable differences between the east and west sides of the Lambert Glacier basin (LGB). The spatial distribution of the surface accumulation is influenced by the atmospheric moisture flux, and by the surface wind field, which is largely determined by topography. Atmospheric water-vapor budget data for the ice-sheet sector covering the basin (45–90˚ E) show that on the east side of the LGB the moisture flux is poleward, averaging 18 kgm–1 s–1 in 1988, while for the west side it is Equatorward, averaging 5 kgm–1 s–1. A similar pattern, but with much lower transport of vapor flux, is seen across 70˚ S. Two firn cores from the east side of the basin and two from the west side were analyzed to determine accumulation-rate and temperature-proxy variations for the past 50 years. The trends were opposite on the different sides of the basin. Similar opposing trends are seen in meteorological records from Davis and Mawson coastal stations, situated on the east and west sides of the LGB respectively. There is a good correlation between the accumulation/18O record in ice cores from the eastern LGB and the sea-level pressure (obtained from the US National Centers for Environmental Prediction/US National Center for Atmospheric Research (NCEP/NCAR) re-analyses) of a Southern Indian Ocean low (SIOL), but not between the SIOL and the records from the western LGB. This study reveals that variations in local circulation could alter at least the annual to decadal time-scale climate records, and may result in completely different climate histories between adjacent areas.
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Azorin-Molina, Cesar, Sergio M. Vicente-Serrano, Tim R. McVicar, Sonia Jerez, Arturo Sanchez-Lorenzo, Juan-I. López-Moreno, Jesus Revuelto, Ricardo M. Trigo, Joan A. Lopez-Bustins, and Fátima Espírito-Santo. "Homogenization and Assessment of Observed Near-Surface Wind Speed Trends over Spain and Portugal, 1961–2011*." Journal of Climate 27, no. 10 (May 9, 2014): 3692–712. http://dx.doi.org/10.1175/jcli-d-13-00652.1.
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Abstract Near-surface wind speed trends recorded at 67 land-based stations across Spain and Portugal for 1961–2011, also focusing on the 1979–2008 subperiod, were analyzed. Wind speed series were subjected to quality control, reconstruction, and homogenization using a novel procedure that incorporated the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)-simulated series as reference. The resultant series show a slight downward trend for both 1961–2011 (−0.016 m s−1 decade−1) and 1979–2008 (−0.010 m s−1 decade−1). However, differences between seasons with declining values in winter and spring, and increasing trends in summer and autumn, were observed. Even though wind stilling affected 77.8% of the stations in winter and 66.7% in spring, only roughly 40% of the declining trends were statistically significant at the p < 0.10 level. On the contrary, increasing trends appeared in 51.9% of the stations in summer and 57.4% in autumn, with also around 40% of the positive trends statistically significant at the p < 0.10 level. In this article, the authors also investigated (i) the possible impact of three atmospheric indices on the observed trends and (ii) the role played by the urbanization growth in the observed decline. An accurate homogenization and assessment of the long-term trends of wind speed is crucial for many fields such as wind energy (e.g., power generation) and agriculture–hydrology (e.g., evaporative demand).
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Boon, John D. "Reducing Wave-Induced Microwave Water-Level Measurement Error with a Least Squares–Designed Digital Filter*." Journal of Atmospheric and Oceanic Technology 31, no. 2 (February 1, 2014): 491–502. http://dx.doi.org/10.1175/jtech-d-13-00160.1.
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Abstract A microwave water-level sensor, the Design Analysis model H-3611i, will soon enter service at tide stations operated by the National Oceanic and Atmospheric Administration’s Center for Operational Oceanographic Products and Services (CO-OPS) as part of the National Water Level Observation Network. CO-OPS tests include a multisensor deployment at the U.S. Army Corps of Engineers Field Research Facility at Duck, North Carolina, to evaluate microwave water-level measurement error over a wide range of Atlantic Ocean sea states. In situ precision and accuracy of processed (6-min average) water level is found to depend on sea state in addition to data processing methods and sensor operating mode. Estimates over selected 6-h measurement periods show that a degree-two polynomial successfully models the increase in sensor standard error with increasing zero-moment (Hm0) wave height but with differences in rate of error increase dependent on the application of a prefilter and choice of sensor operating mode. Prefiltering of 1-Hz “fast mode” sensor output to remove variance at selected wind-wave frequencies can reduce standard error during extreme conditions (Hm0 ≈ 3 m) from approximately ±3 cm without prefiltering to about ±1 cm using a least squares–designed (LSD) digital filter with a 60-s cutoff period. When wave heights are elevated, skewed non-Gaussian distributions develop within the 1-Hz (360 s) sample domain wherein a 3σ outlier elimination process applied without prefiltering can introduce a negative bias of up to 5 cm in individual 6-min water-level averages.
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Davison, Jennifer L., Robert M. Rauber, and Larry Di Girolamo. "A Revised Conceptual Model of the Tropical Marine Boundary Layer. Part II: Detecting Relative Humidity Layers Using Bragg Scattering from S-Band Radar." Journal of the Atmospheric Sciences 70, no. 10 (October 1, 2013): 3025–46. http://dx.doi.org/10.1175/jas-d-12-0322.1.
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Abstract Persistent layers of enhanced equivalent radar reflectivity factor and reduced spectral width were commonly observed within cloud-free regions of the tropical marine boundary layer (TMBL) with the National Center for Atmospheric Research S-Pol radar during the Rain in Cumulus over the Ocean (RICO) field campaign. Bragg scattering is shown to be the primary source of these layers. Two mechanisms are proposed to explain the Bragg scattering layers (BSLs), the first involving turbulent mixing and the second involving detrainment and evaporation of cloudy air. These mechanisms imply that BSLs should exist in layers with tops (bases) defined by local relative humidity (RH) minima (maxima). The relationship between BSLs and RH is explored. An equation for the vertical gradient of radio refractivity N is derived, and a scale analysis is used to demonstrate the close relationship between vertical RH and N gradients. This is tested using the derived radar BSL boundary altitudes, 131 surface-based soundings, and 34 sets of about six near-coincident, aircraft-released dropsondes. First, dropsonde data are used to quantify the finescale variability of the RH field. Then, within limits imposed by this variability, altitudes of tops (bases) of radar BSLs are shown to agree with altitudes of RH minima (maxima). These findings imply that S-band radars can be used to track the vertical profile of RH variations as a function of time and height, that the vertical RH profile of the TMBL is highly variable over horizontal scales as small as 60 km, and that BSLs are a persistent, coherent feature that delineate aspects of TMBL mesoscale structure.
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Elguindi, N., B. Hanson, and D. Leathers. "The Effects of Snow Cover on Midlatitude Cyclones in the Great Plains." Journal of Hydrometeorology 6, no. 3 (June 1, 2005): 263–79. http://dx.doi.org/10.1175/jhm415.1.
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Abstract The impacts of snow cover on the structure and intensity of midlatitude cyclones are examined. The fifth-generation Pennsylvania State University–National Center for Atmospheric Research (Penn State–NCAR) Mesoscale Model (MM5) was used to simulate eight synoptic events in which a well-developed cyclone moved across the central and northern Great Plains region of the United States. Two simulations were performed for each event: a control run with the actual snow cover and a perturbed run with an extensive snow cover. In all of the cases, increasing the snow cover, and thereby reducing the available potential energy, weakened the cyclones. Among the eight cases, the averaged minimum central low pressure of the cyclones in the perturbed runs was approximately 4 mb greater than the control cyclones. The reduction in temperature and moisture in the lower atmosphere was most pronounced in the warm sector, which significantly reduced the thermal and moisture gradients near the surface. This resulted in a weakening of the fronts, less convergence near the surface, and decreased precipitation. Averaged among the cases, the upward vertical velocity near the center of the low was about 3.5 cm s−1 less in the perturbed simulations. Accumulated vertically integrated rainwater was reduced by 0.64 × 109 m3 when averaged for all of the cases in the perturbed simulations. In addition, the weaker gradients across the surface fronts in the increased snow-covered simulations decreased thermal and moisture advection near the surface and may have contributed to limiting the cyclones’ intensification in some of the cases by dampening positive feedback processes between the surface and midtroposphere.
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Grossman-Clarke, Susanne, Yubao Liu, Joseph A. Zehnder, and Jerome D. Fast. "Simulations of the Urban Planetary Boundary Layer in an Arid Metropolitan Area." Journal of Applied Meteorology and Climatology 47, no. 3 (March 1, 2008): 752–68. http://dx.doi.org/10.1175/2007jamc1647.1.
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Abstract A modified version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was applied to the arid Phoenix, Arizona, metropolitan region. The ability of the model to simulate characteristics of the summertime urban planetary boundary layer (PBL) was tested by comparing model results with observations from two field campaigns conducted in May/June 1998 and June 2001. The modified MM5 included a refined land use/cover classification and updated land use data for Phoenix and bulk approaches of characteristics of the urban surface energy balance. PBL processes were simulated by a version of MM5’s Medium-Range Forecast Model (MRF) scheme that was enhanced by new surface flux and nonlocal mixing approaches. Simulated potential temperature profiles were tested against radiosonde data, indicating that the modified MRF scheme was able to simulate vertical mixing and the evolution and height of the PBL with good accuracy and better than the original MRF scheme except in the late afternoon. During both simulation periods, it is demonstrated that the modified MM5 simulated near-surface air temperatures and wind speeds in the urban area consistently and considerably better than the standard MM5 and that wind direction simulations were improved slightly.
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Douglas, Michael W., John Mejia, Norma Ordinola, and Joshua Boustead. "Synoptic Variability of Rainfall and Cloudiness along the Coasts of Northern Peru and Ecuador during the 1997/98 El Niño Event." Monthly Weather Review 137, no. 1 (January 1, 2009): 116–36. http://dx.doi.org/10.1175/2008mwr2191.1.
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Abstract This paper describes the meteorological conditions associated with large fluctuations in rainfall over the coastal regions of northern Peru and Ecuador during the 1997/98 El Niño event. Using data from a network of routine rain gauges and special gauges established just prior to the onset of heavy rains, it is shown that large variations in the daily rainfall on quasi-weekly time scales occurred during the period January–April 1998. These rainfall fluctuations were approximately in phase along the coast from near the equator to ∼7°S. The daily rainfall data was averaged to develop a subset of wet and dry days, and then these dates were used as the basis for compositing. Special pilot balloon observations were composited with respect to the wet and dry days, showing that westerly and northerly wind anomalies are associated with wet spells. Composites of the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and outgoing longwave radiation (OLR) data support a modest association of anomalous westerly wind events with enhanced rainfall. The relationship observed between westerly zonal wind anomalies and rainfall west of the Andes during 1998 suggested using the NCEP reanalysis to develop composites based on westerly wind events observed during other years. Zonal wind anomalies at 700 hPa were used as the primary criterion for stratifying “wet” and “dry” days, despite reservations about the association between rainfall and zonal wind. Compositing Geostationary Operational Environmental Satellite (GOES) and OLR data for 220 west wind anomaly events from the months of January–April for the years 1990–2005 showed that they are associated with enhanced cloudiness that propagates eastward at ∼10 m s−1. The composites using NCEP reanalyses show the evolution of the wind field associated with the wet days and suggest a link between extratropical wave passages across North America and anomalous westerly wind events off the coast of Ecuador and northern Peru.
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Kimura, Gen, Hideaki Takahashi, Kumiko Umemoto, Kazuo Watanabe, Mitsuhito Sasaki, Yusuke Hashimoto, Hiroshi Imaoka, Izumi Ohno, Shuichi Mitsunaga, and Masafumi Ikeda. "Efficacy of S-1 compared to modified FOLFIRINOX as second-line chemotherapy regimens after gemcitabine plus nab-paclitaxel for patients with metastatic pancreatic cancer." Journal of Clinical Oncology 35, no. 4_suppl (February 1, 2017): 449. http://dx.doi.org/10.1200/jco.2017.35.4_suppl.449.
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449 Background: Recently, gemcitabine (GEM) plus nab-paclitaxel (nab-PTX) has been frequently used as a first-line chemotherapy regimen for the treatment of metastatic pancreatic cancer (mPC) in Japan. Nanoliposomal irinotecan combined with 5-fluorouracil and leucovorin (MM-398 plus 5FU/LV) has not yet been approved in Japan. Under these circumstances, a modified FOLFIRINOX (mFFX) regimen or S-1 is commonly used as a second-line chemotherapy regimen for patients with mPC after GEM plus nab-PTX has failed. Methods: Between December 2014 and March 2016, 45 patients with mPC received second-line chemotherapy after the failure of GEM plus nab-PTX (standard dose regimen) at the National Cancer Center Hospital East. Twenty-two patients received mFFX (irinotecan, 150 mg/m2; bolus of 5FU was eliminated), 19 received S-1 (80 mg/m2/d; d1-28, q6w or d1-14, q3w), and 4 received other chemotherapy regimens. The clinical records of the patients were reviewed retrospectively. Results: At baseline, S-1 group had a more severe disease status than the mFFX group (performance status of 0: 21% vs. 68%, P = 0.003; median CA19-9 level: 1832 vs. 577 U/mL, P = 0.30). No significant difference in the response rate (S-1, 5.3% vs. mFFX, 9.1%, P = 0.56) or the disease control rate (S-1, 42% vs. mFFX, 36%, P = 0.71) was seen between the two groups. The progression free survival (PFS) (median: S-1 vs. mFFX: 2.7 vs. 2.4 months (m), P = 0.77), the overall survival (OS) from the second-line treatment (median: 6.1 vs. 6.4m, P = 0.87) and the OS from the first-line treatment (median: 10.9 vs. 12.4m, P = 0.77) were not significantly different between the two groups. These results were similar to those observed for MM-398 plus 5FU/LV (PFS, 3.1m; OS, 6.1m) in a pivotal Phase III study (NAPOLI-1). The incidences of peripheral neuropathy (5.3% vs. 32%, P = 0.04), fatigue (11% vs. 50%, P = 0.007), and neutropenia (11% vs. 64%, P = 0.001) were significantly lower in the S-1 group. Conclusions: S-1 was less toxic than mFFX and exerted a similar anti-tumor effect in the present study. S-1 could be a treatment option for patients with mPC refractory to GEM plus nab-PTX.
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Hughes, Christopher P., and Dana E. Veron. "Characterization of Low-Level Winds of Southern and Coastal Delaware." Journal of Applied Meteorology and Climatology 54, no. 1 (January 2015): 77–93. http://dx.doi.org/10.1175/jamc-d-14-0011.1.
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AbstractWinds across the Delaware Peninsula transport pollutants, modify the temperature, and play a critical role within the state’s agricultural and tourism industries. The low-level winds inland and near Delaware’s coastline are characterized using observations from eight meteorological stations operated by the Delaware Environmental Observing System and the National Data Buoy Center from 2005 through 2012. The low-level winds have pronounced dominant directions during the summer (southwest/southeast) and winter (northwest) seasons, with the greatest spatial and temporal variability occurring in the summer. This inhomogeneity was further investigated with a set of simulations of the low-level winds over the Delaware Bay and surrounding landmass using the Weather Research and Forecasting Model for a subset of days from 2006 through 2012. The model was run with three nests, with the inner nest having a 2-km horizontal resolution. The randomly selected days were organized by synoptic type and season. Mesoscale wind events such as the sea-breeze circulation introduce significant variability in the local wind field of coastal Delaware—an effect that is seen in both observed and modeled data. Southerly winds off Delaware’s coast frequently shift counterclockwise up the Delaware Bay in alignment with the bay coastline. Long-term data from station B44009 (1984–2012) indicate a May decrease (0.03 m s−1 yr−1; significance p = 0.026) and an October increase (0.04 m s−1 yr−1; p = 0.006) of the mean wind speed. Results suggest that the local wind regime is multifaceted and contains significant seasonal, diurnal, and spatial variations.
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Kitagawa, H., Hitoshi Mukai, Yukihiro Nojiri, Yasuyuki Shibata, Toshiyuki Kobayashi, and Tomoko Nojiri. "Seasonal and Secular Variations of Atmospheric 14Co2 Over the Western Pacific Since 1994." Radiocarbon 46, no. 2 (2004): 901–10. http://dx.doi.org/10.1017/s0033822200035943.
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Air sample collections over the western Pacific have continued since 1992 as a part of Center for Global Environmental Research, National Institute for Environmental Studies (CGER-NIES) global environmental monitoring program. The air samples collected on the Japan-Australia transect made it possible to trace the seasonal and secular 14CO2 variations, as well as an increasing trend of greenhouse gases over the western Pacific. A subset of CO2 samples from latitudes of 10–15°N and 23–28°S were chosen for accelerator mass spectrometry (AMS) 14C analysis using a NIES-TERRA AMS with a 0.3–0.4% precision. These 14CO2 records in maritime air show seasonal variations superimposed on normal exponential decreasing trends with a time constant of about 16 yr. The Δ14C values in the Northern Hemisphere are lower those in the Southern Hemisphere by 3–4 during 1994–2002. The Northern Hemisphere record shows relatively high seasonality (2.3 ± 1.5) as compared with the Southern Hemisphere (1.3 ± 1.2). The maximum values of seasonal cycles appear in late autumn and early winter in the Northern and Southern Hemispheres, respectively. Oscillations of 1–10 yr over the western Pacific are found to correlate possibly with the El Niño/Southern Oscillation (ENSO) events.
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Brotzge, J., K. Hondl, B. Philips, L. Lemon, E. J. Bass, D. Rude, and D. L. Andra. "Evaluation of Distributed Collaborative Adaptive Sensing for Detection of Low-Level Circulations and Implications for Severe Weather Warning Operations." Weather and Forecasting 25, no. 1 (February 1, 2010): 173–89. http://dx.doi.org/10.1175/2009waf2222233.1.
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Abstract The Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) is a multiyear engineering research center established by the National Science Foundation for the development of small, inexpensive, low-power radars designed to improve the scanning of the lowest levels (<3 km AGL) of the atmosphere. Instead of sensing autonomously, CASA radars are designed to operate as a network, collectively adapting to the changing needs of end users and the environment; this network approach to scanning is known as distributed collaborative adaptive sensing (DCAS). DCAS optimizes the low-level volume coverage scanning and maximizes the utility of each scanning cycle. A test bed of four prototype CASA radars was deployed in southwestern Oklahoma in 2006 and operated continuously while in DCAS mode from March through June of 2007. This paper analyzes three convective events observed during April–May 2007, during CASA’s intense operation period (IOP), with a special focus on evaluating the benefits and weaknesses of CASA radar system deployment and DCAS scanning strategy of detecting and tracking low-level circulations. Data collected from nearby Weather Surveillance Radar-1988 Doppler (WSR-88D) and CASA radars are compared for mesoscyclones, misocyclones, and low-level vortices. Initial results indicate that the dense, overlapping coverage at low levels provided by the CASA radars and the high temporal (60 s) resolution provided by DCAS give forecasters more detailed feature continuity and tracking. Moreover, the CASA system is able to resolve a whole class of circulations—misocyclones—far better than the WSR-88Ds. In fact, many of these are probably missed completely by the WSR-88D. The impacts of this increased detail on severe weather warnings are under investigation. Ongoing efforts include enhancing the DCAS data quality and scanning strategy, improving the DCAS data visualization, and developing a robust infrastructure to better support forecast and warning operations.
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Uma, Kizhathur Narasimhan, Siddarth Shankar Das, Madineni Venkat Ratnam, and Kuniyil Viswanathan Suneeth. "Assessment of vertical air motion among reanalyses and qualitative comparison with very-high-frequency radar measurements over two tropical stations." Atmospheric Chemistry and Physics 21, no. 3 (February 11, 2021): 2083–103. http://dx.doi.org/10.5194/acp-21-2083-2021.
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Abstract. Vertical wind (w) is one of the most important meteorological parameters for understanding a range of different atmospheric phenomena. Very few direct measurements of w are available so that most of the time one must depend on reanalysis products. In the present study, assessment of w among selected reanalyses (ERA-Interim, ERAi; ERA fifth generation, ERA5; Modern-Era Retrospective analysis for Research and Applications, version 2, MERRA-2; National Center for Atmospheric Research and Depart- ment of Energy reanalysis, NCEP–DOE (R-2); and Japanese 55-year reanalysis, JRA-55) and qualitative comparison of those datasets with VHF radar measurements over the convectively active regions Gadanki, India (13.5∘ N, 79.2∘ E), and Kototabang, Indonesia (0∘ S, 100.2∘ E), are presented for the first time in the troposphere and lower stratosphere. The magnitude of w derived from reanalyses is 10 %–50 % less than that from the radar observations. Radar measurements of w show downdrafts below 8 and 10 km and updrafts above 8–10 km over both locations. Intercomparison between the ensemble of reanalyses with respect to individual reanalysis shows that ERAi, MERRA-2 and JRA-55 compare well with the ensemble compared to ERA5 and NCEP–DOE (R-2). There is no significant improvement in w due to the effect of different spatial sampling for reanalysis data around the Gadanki station. Directional tendency shows that the percentage of updrafts captured is reasonably good, but downdrafts are not well captured by all reanalyses. Thus, caution is advised when using w from reanalyses.
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Koch, Steven E., Cyrille Flamant, James W. Wilson, Bruce M. Gentry, and Brian D. Jamison. "An Atmospheric Soliton Observed with Doppler Radar, Differential Absorption Lidar, and a Molecular Doppler Lidar." Journal of Atmospheric and Oceanic Technology 25, no. 8 (August 1, 2008): 1267–87. http://dx.doi.org/10.1175/2007jtecha951.1.
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Abstract Airborne Leandre II differential absorption lidar (DIAL), S-band dual-polarization Doppler radar (S-Pol), and Goddard Lidar Observatory for Winds (GLOW) Doppler lidar data are used, in conjunction with surface mesonet and special sounding data, to derive the structure and dynamics of a bore and associated solitary wave train (soliton) that were generated in southwestern Kansas during the International H20 Project (IHOP_2002). Vertical cross sections of S-Pol reflectivity, S-Pol radial velocity, and DIAL water vapor mixing ratio show a stunning amplitude-ordered train of trapped solitary waves. DIAL data reveal that the leading wave in the soliton increasingly flattened with time as the soliton dissipated. A method is developed for using the GLOW Doppler winds to obtain the complex two-dimensional vertical circulation accompanying the dissipating soliton. The results show multiple circulations identical in number to the oscillations seen in the S-Pol and DIAL data. The leading updraft occurred precisely at the time that the bore passed over the GLOW facility, as well as when the photon count values suddenly ramped up (suggesting lifting of the low-level inversion by the bore). Additional evidence in support of the validity of the results is provided by the fact that layer displacements computed using the derived vertical motions agree well with those implied by the changes in height of the DIAL mixing ratio surfaces. The depth and speed of propagation of the bore seen in the DIAL and surface mesoanalyses were shown to be consistent with the predictions from bore hydraulic theory. Analysis of National Center for Atmospheric Research (NCAR) Integrated Sounding System (ISS) data shows that a highly pronounced curvature in the profile of bore-relative winds, related to the existence of a very strong low-level jet, effectively trapped the upward leakage of solitary wave energy below 3 km. This finding explains the trapped lee wave–type structures seen in the DIAL, GLOW, and S-Pol data.
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Plummer, David M., Sabine Göke, Robert M. Rauber, and Larry Di Girolamo. "Discrimination of Mixed- versus Ice-Phase Clouds Using Dual-Polarization Radar with Application to Detection of Aircraft Icing Regions*." Journal of Applied Meteorology and Climatology 49, no. 5 (May 1, 2010): 920–36. http://dx.doi.org/10.1175/2009jamc2267.1.
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Abstract Dual-polarization radar measurements and in situ measurements of supercooled liquid water and ice particles within orographic cloud systems are used to develop probabilistic criteria for identifying mixed-phase versus ice-phase regions of sub-0°C clouds. The motivation for this study is the development of quantitative criteria for identification of potential aircraft icing conditions in clouds using polarization radar. The measurements were obtained during the Mesoscale Alpine Programme (MAP) with the National Center for Atmospheric Research S-band dual-polarization Doppler radar (S-Pol) and Electra aircraft. The comparison of the radar and aircraft measurements required the development of an automated algorithm to match radar and aircraft observations in time and space. This algorithm is described, and evaluations are presented to verify its accuracy. Three polarization radar parameters, the radar reflectivity factor at horizontal polarization (ZH), the differential reflectivity (ZDR), and the specific differential phase (KDP), are first separately shown to be statistically distinguishable between conditions in mixed- and ice-phase clouds, even when an estimate of measurement uncertainty is included. Probability distributions for discrimination of mixed-phase versus ice-phase clouds are then developed using the matched radar and aircraft measurements. The probability distributions correspond well to a basic physical understanding of ice particle growth by riming and vapor deposition, both of which may occur in mixed-phase conditions. To the extent that the probability distributions derived for the MAP orographic clouds can be applied to other cloud systems, they provide a simple tool for warning aircraft of the likelihood that supercooled water may be encountered in regions of clouds.
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Demoz, Belay, Cyrille Flamant, Tammy Weckwerth, David Whiteman, Keith Evans, Frédéric Fabry, Paolo Di Girolamo, et al. "The Dryline on 22 May 2002 during IHOP_2002: Convective-Scale Measurements at the Profiling Site." Monthly Weather Review 134, no. 1 (January 1, 2006): 294–310. http://dx.doi.org/10.1175/mwr3054.1.
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Abstract A detailed analysis of the structure of a double dryline observed over the Oklahoma panhandle during the first International H2O Project (IHOP_2002) convective initiation (CI) mission on 22 May 2002 is presented. A unique and unprecedented set of high temporal and spatial resolution measurements of water vapor mixing ratio, wind, and boundary layer structure parameters were acquired using the National Aeronautics and Space Administration (NASA) scanning Raman lidar (SRL), the Goddard Lidar Observatory for Winds (GLOW), and the Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE), respectively. These measurements are combined with the vertical velocity measurements derived from the National Center for Atmospheric Research (NCAR) Multiple Antenna Profiler Radar (MAPR) and radar structure function from the high-resolution University of Massachusetts frequency-modulated continuous-wave (FMCW) radar to reveal the evolution and structure of the late afternoon double-dryline boundary layer. The eastern dryline advanced and then retreated over the Homestead profiling site in the Oklahoma panhandle, providing conditions ripe for a detailed observation of the small-scale variability within the boundary layer and the dryline. In situ aircraft data, dropsonde and radiosonde data, along with NCAR S-band dual-polarization Doppler radar (S-Pol) measurements, are also used to provide the larger-scale picture of the double-dryline environment. Moisture and temperature jumps of about 3 g kg−1 and 1–2 K, respectively, were observed across the eastern radar fine line (dryline), more than the moisture jumps (1–2 g kg−1) observed across the western radar fine line (secondary dryline). Most updraft plumes observed were located on the moist side of the eastern dryline with vertical velocities exceeding 3 m s−1 and variable horizontal widths of 2–5 km, although some were as wide as 7–8 km. These updrafts were up to 1.5 g kg−1 moister than the surrounding environment. Although models suggested deep convection over the Oklahoma panhandle and several cloud lines were observed near the dryline, the dryline itself did not initiate any storms over the intensive observation region (IOR). Possible reasons for this lack of convection are discussed. Strong capping inversion and moisture detrainment between the lifting condensation level and the level of free convection related to an overriding drier air, together with the relatively small near-surface moisture values (less than 10 g kg−1), were detrimental to CI in this case.
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Lima, Maria Andrea, and James W. Wilson. "Convective Storm Initiation in a Moist Tropical Environment." Monthly Weather Review 136, no. 6 (June 1, 2008): 1847–64. http://dx.doi.org/10.1175/2007mwr2279.1.
Full textAbstract:
Abstract Radar and satellite data from the Tropical Rainfall Measuring Mission–Large-Scale Biosphere–Atmosphere (TRMM–LBA) project have been examined to determine causes for convective storm initiation in the southwest Amazon region. The locations and times of storm initiation were based on the National Center for Atmospheric Research (NCAR) S-band dual-polarization Doppler radar (S-Pol). Both the radar and the Geostationary Operational Environmental Satellite-8 (GOES-8) visible data were used to identify cold pools produced by convective precipitation. These data along with high-resolution topographic data were used to determine possible convective storm triggering mechanisms. The terrain elevation varied from 100 to 600 m. Tropical forests cover the area with numerous clear-cut areas used for cattle grazing and farming. This paper presents the results from 5 February 1999. A total of 315 storms were initiated within 130 km of the S-Pol radar. This day was classified as a weak monsoon regime where convection developed in response to the diurnal cycle of solar heating. Scattered shallow cumulus during the morning developed into deep convection by early afternoon. Storm initiation began about 1100 LST and peaked around 1500–1600 LST. The causes of storm initiation were classified into four categories. The most common initiation mechanism was caused by forced lifting by a gust front (GF; 36%). Forcing by terrain (>300 m) without any other triggering mechanism accounted for 21% of the initiations and colliding GFs accounted for 16%. For the remaining 27% a triggering mechanism was not identified. Examination of all days during TRMM–LBA showed that this one detailed study day was representative of many days. A conceptual model of storm initiation and evolution is presented. The results of this study should have implications for other locations when synoptic-scale forcing mechanisms are at a minimum. These results should also have implications for very short-period forecasting techniques in any location where terrain, GFs, and colliding boundaries influence storm evolution.