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1
Fedynets, Vasyl, Ihor Vasylkivskyi, and Yaroslav Yusyk. "Optimization of Gas Dynamical Subsystem of Transducers for Measurement of Gas Flow Temperature." Energy Engineering and Control Systems 2, no. 2 (2016): 43–48. http://dx.doi.org/10.23939/jeecs2016.02.043.
2
SAWATO, Hiroshi, Shinichi TASHIRO, Kazuhiro NAKATA, Manabu TANAKA, Eri YAMAMOTO, Kei YAMAZAKI, and Keiichi SUZUKI. "Measurement of dynamical variation in two-dimensional temperature distribution of TIG pulsed-arcs." QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY 29, no. 3 (2011): 23s—26s. http://dx.doi.org/10.2207/qjjws.29.23s.
3
Heckl, Mareike, Andreas Fix, Matthias Jirousek, Franz Schreier, Jian Xu, and Markus Rapp. "Measurement characteristics of an airborne microwave temperature profiler (MTP)." Atmospheric Measurement Techniques 14, no. 2 (March 1, 2021): 1689–713. http://dx.doi.org/10.5194/amt-14-1689-2021.
Анотація:
Abstract. The microwave temperature profiler (MTP), an airborne passive microwave radiometer, measures radiances, recorded as counts and calibrated to brightness temperatures, in order to estimate temperature profiles around flight altitude. From these data, quantities such as potential temperature gradients and static stability, indicating the state of the atmosphere, can be derived and used to assess important dynamical processes (e.g., gravity waves or stability assessments). DLR has acquired a copy of the MTP from NASA–JPL, which was designed as a wing-canister instrument and is deployed on the German High Altitude LOng range research aircraft (HALO). For this instrument a thorough analysis of instrument characteristics has been made in order to correctly determine the accuracy and precision of MTP measurements. Using a laboratory setup, the frequency response function and antenna diagram of the instrument were carefully characterized. A cold chamber was used to simulate the changing in-flight conditions and to derive noise characteristics as well as reliable calibration parameters for brightness temperature calculations, which are compared to those calculated from campaign data. The MTP shows quite large changes in the instrument state, imposing considerable changes in calibration parameters over the course of a single measurement flight; using a built-in heated target for calibration may yield large errors in brightness temperatures due to a misinterpretation of the measured absolute temperature. Applying the corrections presented herein to the calibration parameter calculations, the measurement noise becomes the dominant source of uncertainty and it is possible to measure the brightness temperatures around flight level (closely related to the absolute temperature close to the instrument) with a precision of 0.38 K. Furthermore, radiative transfer simulations, using the Py4CAtS package in a pencil-beam approach, indicate that the altitude range of the sensitivity of the MTP instrument can be increased by applying a modified measurement strategy. This is the first time such an extensive characterization of an MTP instrument, including a thorough calibration strategy assessment, has been published. The presented results, relevant for the wing-canister design of the MTP instrument, are important when processing MTP data: knowledge of the relevant uncertainties and instrument characteristics is essential for retrieval setup and is mandatory to correctly identify and interpret significant atmospheric temperature fluctuations.
4
Jeon, Min-Gyu, Deog-Hee Doh, Yoshihiro Deguchi, Takahiro Kamimoto, and Minchao Cui. "Evaluation of 3D measurement using CT-TDLAS." Modern Physics Letters B 33, no. 14n15 (May 28, 2019): 1940018. http://dx.doi.org/10.1142/s0217984919400189.
Анотація:
In order to satisfy the requirements of high quality and optimal material manufacturing process, it is important to control the environment of the manufacturing process. Depending on these processes, it is possible to improve the quality of the product by adjusting various gases. With the advent of the tunable laser absorption spectroscopy (TDLAS) technique, the temperature and concentration of the gases can be measured simultaneously. Among them, computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS) is the most important technique for measuring the distributions of temperature and concentration across the two-dimensional planes. This study suggests a three-dimensional measurement to consider the irregular flow of supplying gases. The simultaneous multiplicative algebraic reconstruction technique (SMART) algorithm was used among the CT algorithms. Phantom datasets have been generated by using Gaussian distribution method. It can show expected temperature and concentration distributions. The (HITRAN) database in which the thermo-dynamical properties and the light spectra of H2O are listed were used for the numerical test. The relative average temperature error ratio in the results obtained by the SMART algorithm was about 3.2% for temperature. The maximum error was 86.8 K.
5
Rayner, Nick A., Renate Auchmann, Janette Bessembinder, Stefan Brönnimann, Yuri Brugnara, Francesco Capponi, Laura Carrea, et al. "The EUSTACE Project: Delivering Global, Daily Information on Surface Air Temperature." Bulletin of the American Meteorological Society 101, no. 11 (November 1, 2020): E1924—E1947. http://dx.doi.org/10.1175/bams-d-19-0095.1.
Анотація:
AbstractDay-to-day variations in surface air temperature affect society in many ways, but daily surface air temperature measurements are not available everywhere. Therefore, a global daily picture cannot be achieved with measurements made in situ alone and needs to incorporate estimates from satellite retrievals. This article presents the science developed in the EU Horizon 2020–funded EUSTACE project (2015–19, www.eustaceproject.org) to produce global and European multidecadal ensembles of daily analyses of surface air temperature complementary to those from dynamical reanalyses, integrating different ground-based and satellite-borne data types. Relationships between surface air temperature measurements and satellite-based estimates of surface skin temperature over all surfaces of Earth (land, ocean, ice, and lakes) are quantified. Information contained in the satellite retrievals then helps to estimate air temperature and create global fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place; this needs efficient statistical analysis methods to cope with the considerable data volumes. Daily fields are presented as ensembles to enable propagation of uncertainties through applications. Estimated temperatures and their uncertainties are evaluated against independent measurements and other surface temperature datasets. Achievements in the EUSTACE project have also included fundamental preparatory work useful to others, for example, gathering user requirements, identifying inhomogeneities in daily surface air temperature measurement series from weather stations, carefully quantifying uncertainties in satellite skin and air temperature estimates, exploring the interaction between air temperature and lakes, developing statistical models relevant to non-Gaussian variables, and methods for efficient computation.
6
Will, Johannes, Alexander Gröschel, Christoph Bergmann, and Andreas Magerl. "In Situ Observation of the Oxygen Nucleation in Silicon with X-Ray Single Crystal Diffraction." Solid State Phenomena 178-179 (August 2011): 353–59. http://dx.doi.org/10.4028/www.scientific.net/ssp.178-179.353.
Анотація:
The measurement of Pendellösungs oscillations was used to observe the time dependent nucleation of oxygen in a Czochralski grown single crystal at 750°C. It is shown, that the theoretical approach of the statistical dynamical theory describes the data well. Within the framework of this theory it is possible to determine the static Debye-Waller-factor as a function of the annealing time by evaluating the mean value of the Bragg intensity and the period length. The temperature influence on the Pendellösungs distance was corrected for by measurement of a Float-zone sample at the same temperature.
7
Krolewski, Alex, and Simone Ferraro. "The Integrated Sachs Wolfe effect: unWISE and Planck constraints on dynamical dark energy." Journal of Cosmology and Astroparticle Physics 2022, no. 04 (April 1, 2022): 033. http://dx.doi.org/10.1088/1475-7516/2022/04/033.
Анотація:
Abstract CMB photons redshift and blueshift as they move through gravitational potentials Φ while propagating across the Universe. If the potential is not constant in time, the photons will pick up a net redshift or blueshift, known as the Integrated Sachs-Wolfe (ISW) effect. In the z ≪ 1000 universe, Φ̇ is nonzero on large scales when the Universe transitions from matter to dark energy domination. This effect is only detectable in cross-correlation with large-scale structure at z ∼ 1. In this paper we present a 3.2σ detection of the ISW effect using cross-correlations between unWISE infrared galaxies and Planck CMB temperature maps. We use 3 tomographic galaxy samples spanning 0 < z < 2, allowing us to fully probe the dark energy domination era and the transition into matter domination. This measurement is consistent with ΛCDM (AISW = 0.96 ± 0.30). We study constraints on a particular class of dynamical dark energy models (where the dark energy equation of state is different in matter and dark energy domination), finding that unWISE-ISW improves constraints from type Ia supernovae due to improved constraints on the time evolution of dark energy. When combining with BAO measurements, we obtain the tightest constraints on specific dynamical dark energy models. In the context of a phenomenological model for freezing quintessence, the Mocker model, we constrain the dark energy density within 10% at z < 2 using ISW, BAO and supernovae. Moreover, the ISW measurement itself provides an important independent check when relaxing assumptions about the theory of gravity, as it is sensitive to the gravitational potential rather than the expansion history.
8
Wright, Corwin J., Richard J. Hall, Timothy P. Banyard, Neil P. Hindley, Isabell Krisch, Daniel M. Mitchell, and William J. M. Seviour. "Dynamical and surface impacts of the January 2021 sudden stratospheric warming in novel Aeolus wind observations, MLS and ERA5." Weather and Climate Dynamics 2, no. 4 (December 20, 2021): 1283–301. http://dx.doi.org/10.5194/wcd-2-1283-2021.
Анотація:
Abstract. Major sudden stratospheric warmings (SSWs) are extreme dynamical events where the usual strong westerly winds of the stratospheric polar vortex temporarily weaken or reverse and polar stratospheric temperatures rise by tens of kelvins over just a few days and remain so for an extended period. Via dynamical modification of the atmosphere below them, SSWs are believed to be a key contributor to extreme winter weather events at the surface over the following weeks. SSW-induced changes to the wind structure of the polar vortex have previously been studied in models and reanalyses and in localised measurements such as radiosondes and radars but have not previously been directly and systematically observed on a global scale because of the major technical challenges involved in observing winds from space. Here, we exploit novel observations from ESA's flagship Aeolus wind-profiler mission, together with temperature and geopotential height data from NASA's Microwave Limb Sounder and surface variables from the ERA5 reanalysis, to study the 2021 SSW. This allows us to directly examine wind and related dynamical changes associated with the January 2021 major SSW. Aeolus is the first satellite mission to systematically and directly acquire profiles of wind, and therefore our results represent the first direct measurements of SSW-induced wind changes at the global scale. We see a complete reversal of the zonal winds in the lower to middle stratosphere, with reversed winds in some geographic regions reaching down to the bottom 2 km of the atmosphere. These altered winds are associated with major changes to surface temperature patterns, and in particular we see a strong potential linkage from the SSW to extreme winter weather outbreaks in Greece and Texas during late January and early February. Our results (1) demonstrate the benefits of wind-profiling satellites such as Aeolus in terms of both their direct measurement capability and use in supporting reanalysis-driven interpretation of stratosphere–troposphere coupling signatures, (2) provide a detailed dynamical description of a major weather event, and (3) have implications for the development of Earth-system models capable of accurately forecasting extreme winter weather.
9
Tanaka, Manabu. "Plasma Diagnostics of Arc during MIG Welding of Aluminum." Materials Science Forum 783-786 (May 2014): 2828–32. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.2828.
Анотація:
In this study, distributions of temperature and metal vapor during MIG welding of aluminum are obtained. Since a droplet forms and detaches at a tip of wire, and pass through the arc plasma during MIG welding, dynamic plasma diagnostics are demanded. This study aims to develop method for measuring dynamical variation of two-dimensional distribution of temperature and metal vapor concentration in the arc through optical measurement and to analyze behavior of the metal vapor in MIG welding. As the results, in MIG welding of aluminum, the arc plasma has double structure consisting of high temperature region apart from the arc axis and low temperature region near the arc axis due to influence of the aluminum vapor. Furthermore, the low temperature region near the arc axis occurs because the arc plasma is cooled especially through the intensive radiation loss caused by high concentration of the metal vapor.
10
De Roo, Frederik, and Tirtha Banerjee. "Can a Simple Dynamical System Describe the Interplay between Drag and Buoyancy in Terrain-Induced Canopy Flows?" Journal of the Atmospheric Sciences 75, no. 3 (February 23, 2018): 775–86. http://dx.doi.org/10.1175/jas-d-17-0161.1.
Анотація:
Abstract Under nonneutral stratification and in the presence of topography, the dynamics of turbulent flow within a canopy is not yet completely understood. This has, among other consequences, serious implications for the measurement of surface–atmosphere exchange by means of eddy covariance: for example, the measurement of carbon dioxide fluxes is strongly influenced if drainage flows occur during night, when the flow within the canopy decouples from the flow aloft. An improved physical understanding of the behavior of scalars under canopy turbulence in complex terrain is urgently needed. In the present work, the authors investigate the dynamics of turbulent flow within sloped canopies, focusing on the slope wind and potential temperature. The authors concentrate on the presence of oscillatory behavior in the flow variables in terms of switching of flow regimes by conducting linear stability analysis. The authors revisit and correct the simplified theory that exists in the literature, which is based on the interplay between the drag force and the buoyancy. The authors find that the simplified description of this dynamical system cannot exhibit the observed richness of the dynamics. To augment the simplified dynamical system’s analysis, the authors make use of large-eddy simulation of a three-dimensional hill covered by a homogeneous forest and analyze the phase synchronization behavior of the buoyancy and drag forces in the momentum budget to explore the turbulent dynamics in more detail.
11
Shindo, D., T. Ohishi, S. Iijima, K. Hiraga, T. Oikawa, and M. Kerskei. "Quantitative analysis of diffuse scattering with imaging plate." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1188–89. http://dx.doi.org/10.1017/s0424820100130572.
Анотація:
The excellent properties of the imaging plate (IP), i.e., a wide dynamic range and good linearity for the electron intensity, are promising for quantitative analysis of diffuse scattering since they allow a small dynamical diffraction effect to be evaluated with ‘dynamical factor’. In this paper, we first present accurate measurement of thermal diffuse scattering (TDS), which contributes dominantly to the background of electron diffraction patterns. Secondly, we present a method of extracting weak signal scattering intensities from the background, and apply it to the analysis of diffuse scattering caused from short-range ordered structures.Electron microscope images were obtained with a JEM-2000EXII electron microscope. Image processing was carried out by using a computer system (ACOS 2020) at Tohoku University. Electron diffraction patterns were recorded by using the TEM-IP system (PIXsysTEM). The details of the IP data handling were presented in the previous paper.Figure 1 shows an electron diffraction pattern obtained from an Au thin film ( t ∼ 40nm) at room temperature.
12
Sereno, Mauro, Stefano Ettori, Dominique Eckert, Paul Giles, Ben J. Maughan, Florian Pacaud, Marguerite Pierre, and Patrick Valageas. "The XXL Survey." Astronomy & Astrophysics 632 (November 27, 2019): A54. http://dx.doi.org/10.1051/0004-6361/201628521.
Анотація:
Context. Scaling relations between cluster properties embody the formation and evolution of cosmic structure. Intrinsic scatters and correlations between X-ray properties are determined from merger history, baryonic processes, and dynamical state. Aims. We look for an unbiased measurement of the scatter covariance matrix among the three main X-ray observable quantities attainable in large X-ray surveys: temperature, luminosity, and gas mass. This also gives us the cluster property with the lowest conditional intrinsic scatter at fixed mass. Methods. Intrinsic scatters and correlations can be measured under the assumption that the observable properties of the intra-cluster medium hosted in clusters are log-normally distributed around power-law scaling relations. The proposed method is self-consistent, based on minimal assumptions, and requires neither external calibration by weak lensing, or dynamical or hydrostatic masses, nor the knowledge of the mass completeness. Results. We analysed the 100 brightest clusters detected in the XXL Survey and their X-ray properties measured within a fixed radius of 300 kpc. The gas mass is the less scattered proxy (∼8%). The temperature (∼20%) is intrinsically less scattered than the luminosity (∼30%), but it is measured with a larger observational uncertainty. We found some evidence that gas mass, temperature, and luminosity are positively correlated. Time evolutions are in agreement with the self-similar scenario, but the luminosity–temperature and the gas mass–temperature relations are steeper. Conclusion. Positive correlations between X-ray properties can be determined by the dynamical state and the merger history of the halos. The slopes of the scaling relations are affected by radiative processes.
13
Ajtic, J., B. J. Connor, C. E. Randall, B. N. Lawrence, G. E. Bodeker, J. E. Rosenfield, and D. N. Heuff. "Antarctic air over New Zealand following vortex breakdown in 1998." Annales Geophysicae 21, no. 11 (November 30, 2003): 2175–83. http://dx.doi.org/10.5194/angeo-21-2175-2003.
Анотація:
Abstract. An ozonesonde profile over the Network for Detection of Stratospheric Change (NDSC) site at Lauder (45.0° S, 169.7° E), New Zealand, for 24 December 1998 showed atypically low ozone centered around 24 km altitude (600 K potential temperature). The origin of the anomaly is explained using reverse domain filling (RDF) calculations combined with a PV/O3 fitting technique applied to ozone measurements from the Polar Ozone and Aerosol Measurement (POAM) III instrument. The RDF calculations for two isentropic surfaces, 550 and 600 K, show that ozone-poor air from the Antarctic polar vortex reached New Zealand on 24–26 December 1998. The vortex air on the 550 K isentrope originated in the ozone hole region, unlike the air on 600 K where low ozone values were caused by dynamical effects. High-resolution ozone maps were generated, and their examination shows that a vortex remnant situated above New Zealand was the cause of the altered ozone profile on 24 December. The maps also illustrate mixing of the vortex filaments into southern midlatitudes, whereby the overall mid-latitude ozone levels were decreased.Key words. Atmospheric composition and structure (middle atmosphere composition and chemistry) – Meteorology and atmospheric dynamics (middle atmosphere dynamics)
14
Kleinböhl, A., J. Kuttippurath, M. Sinnhuber, B. M. Sinnhuber, H. Küllmann, K. Künzi, and J. Notholt. "Rapid meridional transport of tropical airmasses to the Arctic during the major stratospheric warming in January 2003." Atmospheric Chemistry and Physics 5, no. 5 (June 1, 2005): 1291–99. http://dx.doi.org/10.5194/acp-5-1291-2005.
Анотація:
Abstract. We present observations of unusually high values of ozone and N2O in the middle stratosphere that were observed by the airborne submillimeter radiometer ASUR in the Arctic. The observations took place in the meteorological situation of a major stratospheric warming that occurred in mid-January 2003 and was dominated by a wave 2 event. On 23 January 2003 the observed N2O and O3 mixing ratios around 69° N in the middle stratosphere reached maximum values of ~190 ppb and ~10 ppm, respectively. The similarities of these N2O profiles in a potential temperature range between 800 and 1200 K with N2O observations around 20° N on 1 March 2003 by the same instrument suggest that the observed Arctic airmasses were transported from the tropics quasi-isentropically. This is confirmed by 5-day back trajectory calculations which indicate that the airmasses between about 800 and 1000 K had been located around 20° N 3–5 days prior to the measurement in the Arctic. Calculations with a linearized ozone chemistry model along calculated as well as idealized trajectories, initialized with the low-latitude ASUR ozone measurements, give reasonable agreement with the Arctic ozone measurement by ASUR. PV distributions suggest that these airmasses did not stay confined in the Arctic region which makes it unlikely that this dynamical situation lead to the formation of dynamically caused pockets of low ozone.
15
Szajnar, J., A. Walasek, and C. Baron. "Tribological and Corrosive Properties of the Parts of Machines with Surface Alloy Layer." Archives of Metallurgy and Materials 58, no. 3 (September 1, 2013): 931–36. http://dx.doi.org/10.2478/amm-2013-0104.
Анотація:
Abstract There are presented the results of researches conducted on the steel cast with surface alloy layer in this work. The measurement of the thickness, hardness and abrasion wear resistance was conducted in accordance with norm ASTM G 65-00. The measurement of the corrosion resistance was conducted in accordance with the potentio - dynamical method. It is shown that it is possible to obtain the alloy surface layer of different thickness by control of some factors: pouring temperature Tzal , diameter of grain of FeCrC alloy Zw and the thickness of the cast wall gśo. It is proved that the smaller diameter of ferrochromium grain, the thicker surface alloy layer. It is also said that the higher pouring temperature and thicker the cast wall, the thicker surface alloy layer. What is more - the smaller thickness of the cast wall, the bigger hardness and abrasion wear resistance.
16
Sato, Kentaro, Masato Matsuura, Masanori Enoki, Kazuyoshi Yamada, and Masaki Fujita. "Dynamical Structure Factor of Magnetic Excitation in Underdoped La1.90Sr0.10CuO4 Measured by Chopper Neutron Spectrometer." Key Engineering Materials 616 (June 2014): 291–96. http://dx.doi.org/10.4028/www.scientific.net/kem.616.291.
Анотація:
We have performed inelastic neutron scattering measurement on high-transition temperature superconductor La1.90Sr0.10CuO4 with utilizing a Fermi chopper spectrometer. We succeeded in converting the observed neutron scattering intensity into a dynamical structure factor in the absolute unit by attempting two methods with analyzing (i) incoherent scattering intensity from the sample itself and (ii) that from vanadium standard. The total squared moment <M2> was evaluated to be 0.176 μB2/Cu, which is much smaller than the value for the parent compound, indicating a markedly change of electronic state by hole-doping.
17
Solomon, A., M. D. Shupe, P. O. G. Persson, and H. Morrison. "Moisture and dynamical interactions maintaining decoupled Arctic mixed-phase stratocumulus in the presence of a humidity inversion." Atmospheric Chemistry and Physics Discussions 11, no. 5 (May 4, 2011): 13469–524. http://dx.doi.org/10.5194/acpd-11-13469-2011.
Анотація:
Abstract. Observations suggest that processes maintaining subtropical and Arctic stratocumulus differ, due to the different environments in which they occur. For example, specific humidity inversions (specific humidity increasing with height) are frequently observed to occur coincident with temperature inversions in the Arctic, while they do not occur in the subtropics. In this study we use nested LES simulations of decoupled Arctic Mixed-Phase Stratocumulus (AMPS) clouds observed during the DOE Atmospheric Radiation Measurement Program's Indirect and SemiDirect Aerosol Campaign (ISDAC) to analyze budgets of water components, potential temperature, and turbulent kinetic energy. These analyses quantify the processes that maintain decoupled AMPS, including the role of the humidity inversions. The results show the maintenance of liquid clouds in both the shallow upper entrainment zone (temperature and humidity inversion) due to a down gradient transport of water vapor by turbulent fluxes into the cloud layer and direct condensation by radiative cooling, and in the updrafts of the mixed-layer eddies below cloud top due to buoyant destabilization. These processes cause at least 20 % of the cloud liquid water to extend into the inversion. The redistribution of water vapor from the top of the humidity inversion to the base of the humidity inversion maintains the cloud layer while the mixed layer-entrainment zone system is continually losing total water. In this decoupled system, the humidity inversion is the only source of water vapor for the cloud system since water vapor from the surface layer is not efficiently transported into the mixed layer. Sedimentation of ice is the dominant sink of moisture from the mixed layer.
18
Liu, Wenzhong, Luis A. Anchordoqui, Eleonora Di Valentino, Supriya Pan, Yabo Wu та Weiqiang Yang. "Constraints from high-precision measurements of the cosmic microwave background: the case of disintegrating dark matter with Λ or dynamical dark energy". Journal of Cosmology and Astroparticle Physics 2022, № 02 (1 лютого 2022): 012. http://dx.doi.org/10.1088/1475-7516/2022/02/012.
Анотація:
Abstract In recent years discrepancies have emerged in measurements of the present-day rate of expansion of the universe H 0 and in estimates of the clustering of matter S 8. Using the most recent cosmological observations we reexamine a novel model proposed to address these tensions, in which cold dark matter disintegrates into dark radiation. The disintegration process is controlled by its rate Q = αℋρddm, where α is a (constant) dimensionless parameter quantifying the strength of the disintegration mechanism and ℋ is the conformal Hubble rate in the spatially flat Friedmann-Lemaître-Robertson-Walker universe and ρddm is the energy density of the disintegrating cold dark matter. We constrain this model with the latest 2018 Planck temperature and polarization data, showing that there is no evidence for α≠ 0 and that it cannot solve the H 0 tension below 3σ, clashing with the result obtained by analyzing the Planck 2015 temperature data. We also investigate two possible extensions of the model in which the dark energy equation-of-state parameter w ≠ -1. In this case it is possible to combine Planck data with the SH0ES measurement, and we demonstrate that in both these models the H 0 tension is resolved at the 1σ level, but the condition w ≠ -1 exacerbates the S 8 tension. We also demonstrate that the addition of intermediate-redshift data (from the Pantheon supernova type Ia dataset and baryon acoustic oscillations) weakens the effectiveness of all these models to address the H 0 and S 8 tensions.
19
Gumbel, Jörg, Linda Megner, Ole Martin Christensen, Nickolay Ivchenko, Donal P. Murtagh, Seunghyuk Chang, Joachim Dillner, et al. "The MATS satellite mission – gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy." Atmospheric Chemistry and Physics 20, no. 1 (January 13, 2020): 431–55. http://dx.doi.org/10.5194/acp-20-431-2020.
Анотація:
Abstract. Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.
20
Solomon, A., M. D. Shupe, P. O. G. Persson, and H. Morrison. "Moisture and dynamical interactions maintaining decoupled Arctic mixed-phase stratocumulus in the presence of a humidity inversion." Atmospheric Chemistry and Physics 11, no. 19 (October 7, 2011): 10127–48. http://dx.doi.org/10.5194/acp-11-10127-2011.
Анотація:
Abstract. Observations suggest that processes maintaining subtropical and Arctic stratocumulus differ, due to the different environments in which they occur. For example, specific humidity inversions (specific humidity increasing with height) are frequently observed to occur near cloud top coincident with temperature inversions in the Arctic, while they do not occur in the subtropics. In this study we use nested LES simulations of decoupled Arctic Mixed-Phase Stratocumulus (AMPS) clouds observed during the DOE Atmospheric Radiation Measurement Program's Indirect and SemiDirect Aerosol Campaign (ISDAC) to analyze budgets of water components, potential temperature, and turbulent kinetic energy. These analyses quantify the processes that maintain decoupled AMPS, including the role of humidity inversions. Key structural features include a shallow upper entrainment zone at cloud top that is located within the temperature and humidity inversions, a mixed layer driven by cloud-top cooling that extends from the base of the upper entrainment zone to below cloud base, and a lower entrainment zone at the base of the mixed layer. The surface layer below the lower entrainment zone is decoupled from the cloud mixed-layer system. Budget results show that cloud liquid water is maintained in the upper entrainment zone near cloud top (within a temperature and humidity inversion) due to a down gradient transport of water vapor by turbulent fluxes into the cloud layer from above and direct condensation forced by radiative cooling. Liquid water is generated in the updraft portions of the mixed-layer eddies below cloud top by buoyant destabilization. These processes cause at least 20% of the cloud liquid water to extend into the inversion. The redistribution of water vapor from the top of the humidity inversion to its base maintains the cloud layer, while the mixed layer-entrainment zone system is continually losing total water. In this decoupled system, the humidity inversion is the only source of water vapor for the cloud system, since water vapor from the surface layer is not efficiently transported into the mixed layer. Sedimentation of ice is the dominant sink of moisture from the mixed layer.
21
Venema, V., S. Bachner, H. W. Rust, and C. Simmer. "Statistical characteristics of surrogate data based on geophysical measurements." Nonlinear Processes in Geophysics 13, no. 4 (September 12, 2006): 449–66. http://dx.doi.org/10.5194/npg-13-449-2006.
Анотація:
Abstract. In this study, the statistical properties of a range of measurements are compared with those of their surrogate time series. Seven different records are studied, amongst others, historical time series of mean daily temperature, daily rain sums and runoff from two rivers, and cloud measurements. Seven different algorithms are used to generate the surrogate time series. The best-known method is the iterative amplitude adjusted Fourier transform (IAAFT) algorithm, which is able to reproduce the measured distribution as well as the power spectrum. Using this setup, the measurements and their surrogates are compared with respect to their power spectrum, increment distribution, structure functions, annual percentiles and return values. It is found that the surrogates that reproduce the power spectrum and the distribution of the measurements are able to closely match the increment distributions and the structure functions of the measurements, but this often does not hold for surrogates that only mimic the power spectrum of the measurement. However, even the best performing surrogates do not have asymmetric increment distributions, i.e., they cannot reproduce nonlinear dynamical processes that are asymmetric in time. Furthermore, we have found deviations of the structure functions on small scales.
22
Di Girolamo, Paolo, Donato Summa, and Rossella Ferretti. "Multiparameter Raman Lidar Measurements for the Characterization of a Dry Stratospheric Intrusion Event." Journal of Atmospheric and Oceanic Technology 26, no. 9 (September 1, 2009): 1742–62. http://dx.doi.org/10.1175/2009jtecha1253.1.
Анотація:
Abstract The University of Basilicata Raman lidar system (BASIL) is operational in Potenza, Italy, and it is capable of performing high-resolution and accurate measurements of atmospheric temperature and water vapor based on the application of the rotational and vibrational Raman lidar techniques in the ultraviolet region. BASIL was recently involved in the 2005 International Lindenberg campaign for Assessment of Humidity and Cloud Profiling Systems and Its Impact on High-Resolution Modeling (LAUNCH 2005) experiment held from 12 September to 31 October 2005. A thorough description of the technical characteristics, measurement capabilities, and performances of BASIL is given in this paper. Measurements were continuously run between 1 and 3 October 2005, covering a dry stratospheric intrusion episode associated with a tropopause folding event. The measurements in this paper represent the first simultaneous Raman lidar measurements of atmospheric temperature, water vapor mixing ratio, and thus relative humidity reported for an extensive observation period (32 h). The use of water vapor to trace intruded stratospheric air allows the clear identification of a dry structure (∼1 km thick) originating in the stratosphere and descending in the free troposphere down to ∼3 km. A similar feature is present in the temperature field, with lower temperature values detected within the dry-air tongue. Relative humidity measurements reveal values as small as 0.5%–1% within the intruded air. The stratospheric origin of the observed dry layer has been verified by the application of a Lagrangian trajectory model. The subsidence of the intruding heavy dry air may be responsible for the gravity wave activity observed beneath the dry layer. Lidar measurements have been compared with the output of both the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) and the European Centre for Medium-Range Weather Forecasts (ECMWF) global model. Comparisons in terms of water vapor reveal the capability of MM5 to reproduce the dynamical structures associated with the stratospheric intrusion episode and to simulate the deep penetration into the troposphere of the dry intruded layer. Moreover, lidar measurements of potential temperature are compared with MM5 output, whereas potential vorticities from both the ECMWF model and MM5 are compared with estimates obtained combining MM5 model vorticity and lidar measurements of potential temperature.
23
Reutter, Philipp, Patrick Neis, Susanne Rohs, and Bastien Sauvage. "Ice supersaturated regions: properties and validation of ERA-Interim reanalysis with IAGOS in situ water vapour measurements." Atmospheric Chemistry and Physics 20, no. 2 (January 23, 2020): 787–804. http://dx.doi.org/10.5194/acp-20-787-2020.
Анотація:
Abstract. Cirrus clouds and their potential formation regions, so-called ice supersaturated regions (ISSRs), with values of relative humidity with respect to ice exceeding 100 %, occur frequently in the tropopause region. It is assumed that ISSRs and cirrus clouds can change the tropopause structure by diabatic processes, driven by latent heating due to phase transition and interaction with radiation. For many research questions, a three-dimensional picture including a sufficient temporal resolution of the water vapour fields in the tropopause region is required. This requirement is fulfilled nowadays by reanalysis products such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. However, for a meaningful investigation of water vapour in the tropopause region, a comparison of the reanalysis data with measurement is advisable, since it is difficult to measure water vapour and to assimilate meaningful measurements into reanalysis products. Here, we present an intercomparison of high-resolution in situ measurements aboard passenger aircraft within the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org, last access: 15 January 2020) with ERA-Interim. Temperature and humidity data over the North Atlantic from 2000 to 2009 are compared relative to the dynamical tropopause. The comparison of the temperature shows good agreement between the measurement and ERA-Interim. While ERA-Interim also shows the main features of the water vapour measurements of IAGOS, the variability of the data is clearly smaller in the reanalysis data set. The combination of temperature and water vapour leads to the relative humidity with respect to ice (RHi). Here, ERA-Interim deviates from the measurements concerning values larger than RHi=100 %, both in number and strength of supersaturation. Also, pathlengths of ISSRs along flight tracks are investigated, representing macrophysical properties as linked to atmospheric flows. The comparison of ISSR pathlengths shows distinct differences, which can be traced back to the spatial resolution of both data sets. Also, the seasonal cycle and height dependence of pathlengths changes for the different data sets due to their spatial resolution. IAGOS shows a significantly greater amount of smaller ISSRs compared to ERA-Interim. Good agreement begins only at pathlengths on the order of the ERA-Interim spatial resolution and larger.
24
Franzen, Christoph, Robert Edward Hibbins, Patrick Joseph Espy, and Anlaug Amanda Djupvik. "Optimizing hydroxyl airglow retrievals from long-slit astronomical spectroscopic observations." Atmospheric Measurement Techniques 10, no. 8 (August 25, 2017): 3093–101. http://dx.doi.org/10.5194/amt-10-3093-2017.
Анотація:
Abstract. Astronomical spectroscopic observations from ground-based telescopes contain background emission lines from the terrestrial atmosphere's airglow. In the near infrared, this background is composed mainly of emission from Meinel bands of hydroxyl (OH), which is produced in highly excited vibrational states by reduction of ozone near 90 km. This emission contains a wealth of information on the chemical and dynamical state of the Earth's atmosphere. However, observation strategies and data reduction processes are usually optimized to minimize the influence of these features on the astronomical spectrum. Here we discuss a measurement technique to optimize the extraction of the OH airglow signal itself from routine J-, H-, and K-band long-slit astronomical spectroscopic observations. As an example, we use data recorded from a point-source observation by the Nordic Optical Telescope's intermediate-resolution spectrograph, which has a spatial resolution of approximately 100 m at the airglow layer. Emission spectra from the OH vibrational manifold from v′ = 9 down to v′ = 3, with signal-to-noise ratios up to 280, have been extracted from 10.8 s integrations. Rotational temperatures representative of the background atmospheric temperature near 90 km, the mesosphere and lower thermosphere region, can be fitted to the OH rotational lines with an accuracy of around 0.7 K. Using this measurement and analysis technique, we derive a rotational temperature distribution with v′ that agrees with atmospheric model conditions and the preponderance of previous work. We discuss the derived rotational temperatures from the different vibrational bands and highlight the potential for both the archived and future observations, which are at unprecedented spatial and temporal resolutions, to contribute toward the resolution of long-standing problems in atmospheric physics.
25
Tang, Y. L., L. J. Shen, D. W. Lu, K. C. Hung, X. Jin, X. X. Xuu, H. M. Shao, C. C. Lam, L. J. Shen та K. C. Hung. "Voltage Response of AC Susceptibility and Pinning Effects in Hg0.69Pb0.31Ba2Ca2Cu3O8+δ". Australian Journal of Physics 53, № 5 (2000): 707. http://dx.doi.org/10.1071/ph00020.
Анотація:
We have studied the voltage response of AC susceptibility,and from the imaginary part of the susceptibility experimental results a new method is presented in terms of the material equation to investigate the pinning properties and the dynamical response in our Hg 0.69 Pb 0.31 Ba 2 Ca 2 Cu 3 O 8+δ sample. We also discuss the differences between the voltage criterion and our AC response measurement method in order to determine the value of the true critical current density. The result shows that the later method reflects the true critical state of high-temperature superconductivity better than the general voltage criterion.
26
Funke, Bernd, William Ball, Stefan Bender, Angela Gardini, V. Lynn Harvey, Alyn Lambert, Manuel López-Puertas, et al. "HEPPA-II model–measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008–2009." Atmospheric Chemistry and Physics 17, no. 5 (March 14, 2017): 3573–604. http://dx.doi.org/10.5194/acp-17-3573-2017.
Анотація:
Abstract. We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80 km) atmospheric models with observations of odd nitrogen (NOx = NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, and SMR on Odin) during the Northern Hemisphere (NH) polar winter 2008/2009. The models included in the comparison are the 3-D chemistry transport model 3dCTM, the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the modelling tools for SOlar Climate Ozone Links studies (SOCOL and CAO-SOCOL), and the Whole Atmosphere Community Climate Model (WACCM4). The comparison focuses on the energetic particle precipitation (EPP) indirect effect, that is, the polar winter descent of NOx largely produced by EPP in the mesosphere and lower thermosphere. A particular emphasis is given to the impact of the sudden stratospheric warming (SSW) in January 2009 and the subsequent elevated stratopause (ES) event associated with enhanced descent of mesospheric air. The chemistry climate model simulations have been nudged toward reanalysis data in the troposphere and stratosphere while being unconstrained above. An odd nitrogen upper boundary condition obtained from MIPAS observations has further been applied to medium-top models. Most models provide a good representation of the mesospheric tracer descent in general, and the EPP indirect effect in particular, during the unperturbed (pre-SSW) period of the NH winter 2008/2009. The observed NOx descent into the lower mesosphere and stratosphere is generally reproduced within 20 %. Larger discrepancies of a few model simulations could be traced back either to the impact of the models' gravity wave drag scheme on the polar wintertime meridional circulation or to a combination of prescribed NOx mixing ratio at the uppermost model layer and low vertical resolution. In March–April, after the ES event, however, modelled mesospheric and stratospheric NOx distributions deviate significantly from the observations. The too-fast and early downward propagation of the NOx tongue, encountered in most simulations, coincides with a temperature high bias in the lower mesosphere (0.2–0.05 hPa), likely caused by an overestimation of descent velocities. In contrast, upper-mesospheric temperatures (at 0.05–0.001 hPa) are generally underestimated by the high-top models after the onset of the ES event, being indicative for too-slow descent and hence too-low NOx fluxes. As a consequence, the magnitude of the simulated NOx tongue is generally underestimated by these models. Descending NOx amounts simulated with medium-top models are on average closer to the observations but show a large spread of up to several hundred percent. This is primarily attributed to the different vertical model domains in which the NOx upper boundary condition is applied. In general, the intercomparison demonstrates the ability of state-of-the-art atmospheric models to reproduce the EPP indirect effect in dynamically and geomagnetically quiescent NH winter conditions. The encountered differences between observed and simulated NOx, CO, and temperature distributions during the perturbed phase of the 2009 NH winter, however, emphasize the need for model improvements in the dynamical representation of elevated stratopause events in order to allow for a better description of the EPP indirect effect under these particular conditions.
27
Ding, Jiong, Suijun Yang, and Shuliang Ye. "A Fast-Multi-Channel Sub-Millikelvin Precision Resistance Thermometer Readout Based on the Round-Robin Structure." Measurement Science Review 18, no. 4 (August 1, 2018): 138–46. http://dx.doi.org/10.1515/msr-2017-0020.
Анотація:
Abstract The fast response multipoint high-precision temperature measurement is often necessary in many dynamical measurement fields and industrial applications. However, limited by the existing electric circuit architecture, either the AC or DC bridges have the shortcoming that the rates or precisions degenerate markedly in the multi-channel scanning mode. To overcome this disadvantage, a round-robin structural low-cost ratiometric resistance thermometer readout based on several commercial 32-bit sigma-delta analogue-to-digital converters (Σ-Δ ADCs) was presented in this article. The experimental results show that the precision of this readout corresponds to 0.1 mK at 1 Hz when sampling four channel resistors simultaneously, while the precision and rate are not degenerating with the channel number increasing. In addition, the uncertainty of the readout is investigated in this article. It shows that the presented readout can achieve an uncertainty as low as 2.1 mK at 1 Hz (K = 2).
28
Gubenko, V. N., A. G. Pavelyev, R. R. Salimzyanov, and A. A. Pavelyev. "Reconstruction of internal gravity wave parameters from radio occultation retrievals of vertical temperature profiles in the Earth atmosphere." Atmospheric Measurement Techniques Discussions 4, no. 2 (March 1, 2011): 1397–425. http://dx.doi.org/10.5194/amtd-4-1397-2011.
Анотація:
Abstract. The new method for the reconstruction of internal gravity wave (IGW) parameters from a single vertical temperature profile measurement in the Earth atmosphere has been developed. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, then analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitude thresholds of the temperature wave field and on the linear IGW saturation theory in which amplitude thresholds are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal gravity wave reaches the shear instability limit, energy is assumed to be dissipated in such a way that the amplitude is maintained at the instability limit as the wave propagates upwards. In order to approbate the method we have used in situ data of simultaneous balloon high-resolution measurements of the temperature and wind velocity in the Earth stratosphere (France) where a long-period inertia-gravity wave has been detected. Using the temperature data only, we have reconstructed all the measured wave parameters with uncertainties not larger than 30%. An application of the method to the radio occultation data has given the possibility to identify the IGWs in the Earth stratosphere and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal perturbations of the wind velocity, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy, vertical fluxes of the wave energy and horizontal momentum. The obtained results of internal wave studies in the Earth stratosphere deduced from the COSMIC and CHAMP GPS occultation temperature profiles have been presented and discussed.
29
Moradi, Isaac, K. Franklin Evans, Will McCarty, Marangelly Cordero-Fuentes, Ronald Gelaro, and Robert A. Black. "Assimilation of Satellite Microwave Observations over the Rainbands of Tropical Cyclones." Monthly Weather Review 148, no. 12 (December 2020): 4729–45. http://dx.doi.org/10.1175/mwr-d-19-0341.1.
Анотація:
AbstractA novel Bayesian Monte Carlo integration (BMCI) technique was developed to retrieve geophysical variables from satellite microwave radiometer data in the presence of tropical cyclones. The BMCI technique includes three steps: generating a stochastic database, simulating satellite brightness temperatures using a radiative transfer model, and retrieving geophysical variables such as profiles of temperature, relative humidity, and cloud liquid and ice water content from real observations. The technique also provides uncertainty estimates for each retrieval and can output the error covariance matrix of selected parameters. The measurements from the Advanced Technology Microwave Sounder (ATMS) on board Suomi National Polar-Orbiting Partnership (Suomi NPP) and the Global Precipitation Measurement (GPM) Microwave Imager (GMI) were used as input. A new technique was developed to correct the ATMS and GMI observations for the beam-filling effect, which is due to small-scale variability of precipitation and clouds when compared with the instrument footprint and also the nonlinear relation between the brightness temperature and precipitation. In addition, the assimilation of the BMCI retrievals into the NASA GEOS model is discussed for Hurricane Maria. The results show that assimilating the BMCI retrievals can influence the dynamical features of the cyclone, including a stronger warm core, a symmetric eye, and vertically aligned wind columns. Two possible factors that may limit the impact of the BMCI retrievals include 1) the resolution of the model (about 25 km), which was too coarse to show the potential of the BMCI data in improving the representation of tropical storms in the model forecast, and 2) the data assimilation system not being able to consider vertically correlated observation errors.
30
Pisso, I., K. S. Law, F. Fierli, P. H. Haynes, P. Hoor, E. Palazzi, F. Ravegnani, and S. Viciani. "On the structure of the extra-tropical transition layer from in-situ observations." Atmospheric Chemistry and Physics Discussions 12, no. 10 (October 25, 2012): 28033–68. http://dx.doi.org/10.5194/acpd-12-28033-2012.
Анотація:
Abstract. In-situ observations of atmospheric tracers from multiple measurement campaigns over the period 1994–2007 were combined to investigate the Extra-tropical Transition Layer (ExTL) region and the properties of large scale meridional transport. We used potential temperature, equivalent latitude and distance relative to the local dynamical tropopause as vertical coordinates to highlight the behaviour of trace gases in the tropopause region. Vertical coordinates based on constant PV surfaces allowed us to relate the dynamical definition of the tropopause with trace gases distributions and vertical gradients and hence analyse its latitudinal dependence and seasonal variability. Analysis of the available data provides a working definition of the upper limit of the ExTL based on the upper limit of the region of high vertical CO gradient in PV relative coordinates. A secondary local maximum in vertical O3 gradient can be used a proxy for the lower limit, although it is less clearly defined than that of CO. The sloping isopleths of CO and O3 mixing ratios and the CO mixing ratio gradient are consistent with isopleths in purely dynamical diagnostics such as χ30 d, the proportion of air masses in contact with the PBL within one month and underline the differences between the PV based and chemical tropopauses. The use of tropopause relative coordinates allows different seasons to be analysed together to produce climatological means. The weak dependence of dynamical diagnostics of transport on the absolute values of tracer concentrations makes them a suitable process-oriented tool to evaluate global chemical models and make Lagrangian comparisons.
31
Jocher, Georg, Florian Karner, Christoph Ritter, Roland Neuber, Klaus Dethloff, Friedrich Obleitner, Joachim Reuder, and Thomas Foken. "The Near-Surface Small-Scale Spatial and Temporal Variability of Sensible and Latent Heat Exchange in the Svalbard Region: A Case Study." ISRN Meteorology 2012 (July 19, 2012): 1–14. http://dx.doi.org/10.5402/2012/357925.
Анотація:
We present data from two eddy covariance systems for determining the sensible and latent heat flux and the shear stress near the earth's surface. One measures continuously since September 2010 close to the village Ny-Ålesund, Svalbard, the other one was located on Kongsvegen glacier for a short period in April 2011. Two examples for small-scale variability are discussed: near surface external gravity waves associated with katabatic wind from the Broggerbreen glacier located a few kilometres southwestern of Ny-Ålesund, and an episode when the two eddy systems at the different measurement sites captured very different conditions at the same time. In case of gravity wave motion the eddy covariance method results in fictitious positive fluxes due to the strong correlation between temperature and vertical wind, which has to be considered carefully. The comparison between the two sites showed that generally the dynamical processes near the Earth’s surface for Ny-Ålesund and the Kongsvegen glacier are different and local. But there are also cases of synchronization due to synoptic influences, and then the same processes are visible at the two measurement sites. Both examples show that the boundary layer in Ny-Ålesund is not only affected by the main glaciers in the east of the village, but also by other orographical characteristics and synoptic issues. Therefore, the only meaningful way to deal with point measurements is to consider them in context with the surrounding orography and the general meteorological conditions.
32
Gubenko, V. N., A. G. Pavelyev, R. R. Salimzyanov, and A. A. Pavelyev. "Reconstruction of internal gravity wave parameters from radio occultation retrievals of vertical temperature profiles in the Earth's atmosphere." Atmospheric Measurement Techniques 4, no. 10 (October 14, 2011): 2153–62. http://dx.doi.org/10.5194/amt-4-2153-2011.
Анотація:
Abstract. A new method for the reconstruction of internal gravity wave (IGW) parameters from a single vertical temperature profile measurement in the Earth's atmosphere has been developed. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, then analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitude thresholds of the temperature wave field and on the linear IGW saturation theory in which amplitude thresholds are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal gravity wave reaches the shear instability limit, energy is assumed to be dissipated in such a way that the amplitude is maintained at the instability limit as the wave propagates upwards. In order to approbate the method we have used data of simultaneous high-resolution balloon measurements of the temperature and wind velocity in the Earth's stratosphere over France where a long-period inertia-gravity wave has been detected. Using the radiosonde temperature data only, we have reconstructed all wave parameters, which were determined by radiosondes, with relative deviations not larger than 30%. An application of the method to the radio occultation (RO) data has given the possibility to identify the IGWs in the Earth's stratosphere and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal perturbations of the wind velocity, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy, vertical fluxes of the wave energy and horizontal momentum. The obtained results of internal wave studies in the Earth's stratosphere deduced from the COSMIC and CHAMP GPS occultation temperature profiles are presented and discussed.
33
Meisehen, T., F. Bühler, R. Koppmann, and M. Krebsbach. "An analytical system for the measurement of stable hydrogen isotopes in ambient volatile organic compounds." Atmospheric Measurement Techniques 8, no. 10 (October 23, 2015): 4475–86. http://dx.doi.org/10.5194/amt-8-4475-2015.
Анотація:
Abstract. Stable isotope measurements in atmospheric volatile organic compounds (VOCs) are an excellent tool to analyse chemical and dynamical processes in the atmosphere. While up to now isotope studies of VOCs in ambient air have mainly focussed on carbon isotopes, we herein present a new measurement system to investigate hydrogen isotope ratios in atmospheric VOCs. This system, consisting of a gas chromatography pyrolysis isotope ratio mass spectrometer (GC-P-IRMS) and a pre-concentration system, was thoroughly characterised using a VOC test mixture. A precision of better than 9 ‰ (in δ 2H) is achieved for n-pentane, 2-methyl-1,3-butadiene (isoprene), n-heptane, 4-methyl-pentane-2-one (4-methyl-2-pentanone), methylbenzene (toluene), n-octane, ethylbenzene, m/p-xylene and 1,2,4-trimethylbenzene. A comparison with independent measurements via elemental analysis shows an accuracy of better than 9 ‰ for n-pentane, n-heptane, 4-methyl-2-pentanone, toluene and n-octane. Above a minimum required pre-concentrated compound mass the obtained δ 2H values are constant within the standard deviations. In addition, a remarkable influence of the pyrolysis process on the isotope ratios is found and discussed. Reliable measurements are only possible if the ceramic tube used for the pyrolysis is sufficiently conditioned, i.e. the inner surface is covered with a carbon layer. It is essential to verify this conditioning regularly and to renew it if required. Furthermore, influences of a necessary H3+ correction and the pyrolysis temperature on the isotope ratios are discussed. Finally, the applicability to measure hydrogen isotope ratios in VOCs at ambient levels is demonstrated with measurements of outside air on 5 different days in February and March 2015. The measured hydrogen isotope ratios range from −136 to −105 ‰ forn-pentane, from −86 to −63 ‰ for toluene, from −39 to −15 ‰ for ethylbenzene, from −99 to −68 ‰ for m/p-xylene and from −45 to −34 ‰ for o-xylene.
34
Meisehen, T., F. Bühler, R. Koppmann, and M. Krebsbach. "An analytical system for the measurement of stable hydrogen isotopes in ambient volatile organic compounds." Atmospheric Measurement Techniques Discussions 8, no. 7 (July 10, 2015): 7093–125. http://dx.doi.org/10.5194/amtd-8-7093-2015.
Анотація:
Abstract. Stable isotope measurements in atmospheric volatile organic compounds (VOC) are an excellent tool to analyse chemical and dynamical processes in the atmosphere. While up to now isotope studies of VOC in ambient air mainly focus on carbon isotopes, we herein present a new measurement system to investigate hydrogen isotope ratios in atmospheric VOC. This system consisting of a GC-P-IRMS (Gas Chromatography Pyrolysis Isotope Ratio Mass Spectrometer) and a preconcentration system was thoroughly characterised using a working standard. A precision of better than 9 ‰ (in δD) is achieved for n-pentane, 2-methyl-1,3-butadiene (isoprene), n-heptane, 4-methyl-pentane-2-one (4-methyl-2-pentanone), methylbenzene (toluene), n-octane, ethylbenzene, m/p-xylene, and 1,2,4-trimethylbenzene. A comparison with independent measurements via elemental analysis shows an accuracy of better than 9 ‰ for n-pentane, n-heptane, 4-methyl-2-pentanone, toluene, and n-octane. Above a compound specific minimum peak area the obtained δD values are constant within the standard deviations. In addition, a remarkable influence of the pyrolysis process on the isotope ratios is found and discussed. Reliable measurements are only possible if the ceramic tube used for the pyrolysis is sufficiently conditioned, i.e. the inner surface is covered with a carbon layer. It is essential to verify this conditioning regularly and to renew it if required. Furthermore, influences of a necessary H3&plus; correction and the pyrolysis temperature on the isotope ratios are discussed. Finally, the applicability to measure hydrogen isotope ratios in VOC at ambient levels is demonstrated with measurements of outside air on five different days in February and March 2015. The measured hydrogen isotope ratios range from −136 to −105 ‰ for n-pentane, from −86 to −63 ‰ for toluene, from −39 to −15 ‰ for ethylbenzene, from −99 to −68 ‰ for m/p-xylene, and from −45 to −34 ‰ for o-xylene.
35
Ungermann, J., J. Blank, M. Dick, A. Ebersoldt, F. Friedl-Vallon, A. Giez, T. Guggenmoser, et al. "Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra." Atmospheric Measurement Techniques Discussions 7, no. 12 (December 2, 2014): 12037–80. http://dx.doi.org/10.5194/amtd-7-12037-2014.
Анотація:
Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 research aircraft HALO during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra. 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line-of-sight. Simultaneous in-situ observations by the BAsic HALO Measurement And Sensor System (BAHAMAS), the Fast In-Situ Stratospheric Hygrometer (FISH), FAIRO, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in-situ trace gas data, and discrepancies can to a large fraction be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.
36
Banaszak, David, and Michael Camden. "Static and Dynamic Calibration of Pressure Transducers at Elevated Temperatures." Journal of the IEST 38, no. 4 (July 31, 1995): 23–30. http://dx.doi.org/10.17764/jiet.2.38.4.u61473348th04987.
Анотація:
The Air Force conducts tests requiring measurement of high dynamic pressures in high-temperature environments. Such tests require measurement of dynamic pressures created by jet engines, turbulent air-flow along hot areas of aircraft structures, and acoustic levels in Air Force test chambers such as acoustic chambers, wind tunnels, and engine test stands. Several commercial industries also have requirements for high-temperature dynamic measurements. To address these Air Force needs for dynamic pressure measurements at high temperatures, the Structures Division of the Flight Dynamics Directorate of the Wright Laboratory evaluated dynamic pressure transducers for use in extreme acoustic and thermal environments. Transducer manufacturers were surveyed and three off-the-shelf pressure transducers capable of measuring dynamic pressures at extreme environments were identified. The first model measures up to 194 dB(A) and operates up to 260°C (500°F). This model has an extended operating temperature up to 1649°C (3000 °F) when used with a water-cooled jacket. The second model is an air-cooled transducer advertised to operate up to 593°C (1100°F). The third model is a water-cooled transducer advertised to operate up to 2802°C (5075 °F). Two of the models have low sensitivity and thus require more output amplification. These two models are also larger and require larger mounting holes. The transducers were evaluated at various static pressures, acoustic levels, and temperatures. This paper describes the procedures used to calibrate these transducers up to a 172-dB sound pressure level (SPL) and a temperature of 732°C (1350°F). The results for these transducers are summarized for different static pressures, operating SPLs, and temperatures.
37
Hoffmann, C. G., U. Raffalski, M. Palm, B. Funke, S. H. W. Golchert, G. Hochschild, and J. Notholt. "Observation of strato-mesospheric CO above Kiruna with ground-based microwave radiometry – retrieval and satellite comparison." Atmospheric Measurement Techniques 4, no. 11 (November 8, 2011): 2389–408. http://dx.doi.org/10.5194/amt-4-2389-2011.
Анотація:
Abstract. CO serves as a tracer for dynamics in the polar winter middle atmosphere. This work presents the retrieval and the characterization of ground-based CO measurements from the winters 2008/2009 and 2009/2010 by the Kiruna microwave radiometer KIMRA, located in northern Sweden (67.8° N, 20.4° E). Furthermore, the dataset is used for an extensive comparison to the recent satellite instruments MLS on Aura, ACE-FTS, and MIPAS on Envisat. The vmr profiles are retrieved using the optimal estimation approach. A detailed analysis of the averaging kernel functions is carried out, showing sensitivity of the measurements between 40 and 80 km altitude, a vertical resolution of 16 to 22 km, as well as a residual influence of the region up to 130 km altitude. An error assessment reveals a total error of the retrieved profile that increases with altitude and is approx. ±0.1 ppmv at 50 km altitude and ±3 ppmv at 80 km altitude. The main contributions to this total error arise from the measurement noise and the uncertainty of the used temperature profiles. The expected dynamical features of the polar winter middle atmosphere are qualitatively identified in the retrieved time series, but are not quantitatively analyzed here. The dense MLS dataset is used to investigate the influence of the collocation criteria on the satellite comparison, showing that relaxing the distance criterion causes a high bias for MLS. The comparison including the other instruments is difficult because of the small number of coincidences. However, it suggests that there is a general agreement between KIMRA and the satellite instruments below 65 km altitude, but a high bias for KIMRA above this altitude. Furthermore, the shape of the KIMRA profile appears to be systematically different from the satellite profiles.
38
Hoffmann, C. G., U. Raffalski, M. Palm, B. Funke, S. H. W. Golchert, G. Hochschild, and J. Notholt. "Observation of strato-mesospheric CO above Kiruna with ground-based microwave radiometry – retrieval and satellite comparison." Atmospheric Measurement Techniques Discussions 4, no. 4 (July 6, 2011): 4209–67. http://dx.doi.org/10.5194/amtd-4-4209-2011.
Анотація:
Abstract. CO serves as a tracer for dynamics in the polar winter middle atmosphere. This work presents the retrieval and the characterization of ground-based CO measurements from the winters 2008/2009 and 2009/2010 by the Kiruna microwave radiometer KIMRA, located in northern Sweden (67.8° N, 20.4° E). Furthermore, the dataset is used for an extensive comparison to the recent satellite instruments MLS on Aura, ACE-FTS, and MIPAS on Envisat. The vmr profiles are retrieved using the Optimal Estimation approach. A detailed analysis of the averaging kernel functions is carried out, showing sensitivity of the measurements between 40 and 80 km altitude, a vertical resolution of 16 to 22 km, as well as a residual influence of the region up to 130 km altitude. An error assessment reveals a total error of the retrieved profile that increases with altitude and is approx. ±0.1 ppmv at 50 km altitude and ±3 ppmv at 80 km altitude. The main contributions to this total error arise from the measurement noise and the uncertainty of the used temperature profiles. The expected dynamical features of the polar winter middle atmosphere are qualitatively identified in the retrieved time series, but are not quantitatively analyzed here. The dense MLS dataset is used to investigate the influence of the collocation criteria on the satellite comparison, showing that relaxing the distance criterion causes a high bias for MLS. The comparison including the other instruments is difficult because of the small number of coincidences. However, it suggests that there is a general agreement between KIMRA and the satellite instruments below 65 km altitude, but a high bias for KIMRA above this altitude. Furthermore, the shape of the KIMRA profile appears to be systematically different from the satellite profiles.
39
Lin, Pu, Qiang Fu, Susan Solomon, and John M. Wallace. "Temperature Trend Patterns in Southern Hemisphere High Latitudes: Novel Indicators of Stratospheric Change." Journal of Climate 22, no. 23 (December 1, 2009): 6325–41. http://dx.doi.org/10.1175/2009jcli2971.1.
Анотація:
Abstract Robust stratospheric temperature trend patterns are suggested in the winter and spring seasons in the Southern Hemisphere high latitudes from the satellite-borne Microwave Sounding Unit (MSU) measurement for 1979–2007. These patterns serve as indicators of key processes governing temperature and ozone changes in the Antarctic. The observed patterns are characterized by cooling and warming regions of comparable magnitudes, with the strongest local trends occurring in September and October. In September, ozone depletion induces radiative cooling, and strengthening of the Brewer–Dobson circulation (BDC) induces dynamical warming. Because the trends induced by these two processes are centered in different locations in September, they do not cancel each other, but rather produce a wavelike structure. In contrast, during October, the ozone-induced radiative cooling and the BDC-induced warming exhibit a more zonally symmetric structure than in September, and hence largely cancel each other. However, the October quasi-stationary planetary wavenumber 1 has shifted eastward from 1979 to 2007, producing a zonal wavenumber-1 trend structure, which dominates the observed temperature trend pattern. Simulated temperature changes for 1979–2007 from coupled atmosphere–ocean general circulation model (AOGCM) experiments run for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) are compared with the observations. In general, the simulated temperature changes are dominated by zonally symmetric ozone-induced radiative cooling. The models fail to simulate the warming in the southern polar stratosphere, implying a lack of the BDC strengthening in these models. They also fail to simulate the quasi-stationary planetary wave changes observed in October and November.
40
Hübner, J., J. Olesch, H. Falke, F. X. Meixner, and T. Foken. "A horizontal mobile measuring system for atmospheric quantities." Atmospheric Measurement Techniques 7, no. 9 (September 16, 2014): 2967–80. http://dx.doi.org/10.5194/amt-7-2967-2014.
Анотація:
Abstract. A fully automatic horizontal mobile measuring system (HMMS) for atmospheric quantities has been developed. The HMMS is based on the drive mechanism of a garden railway system and can be installed at any location and along any measuring track. In addition to meteorological quantities (temperature, humidity and short-/long-wave down/upwelling radiation), HMMS also measures trace gas concentrations (carbon dioxide and ozone). While sufficient spatial resolution is a problem even for measurements on distributed towers, this could be easily achieved with the HMMS, which has been specifically developed to obtain higher information density about horizontal gradients in a heterogeneous forest ecosystem. There, horizontal gradients of meteorological quantities and trace gases could be immense, particularly at the transition from a dense forest to an open clearing, with large impact on meteorological parameters and exchange processes. Consequently, HMMS was firstly applied during the EGER IOP3 project (ExchanGE processes in mountainous Regions – Intense Observation Period 3) in the Fichtelgebirge Mountains (SE Germany) during summer 2011. At a constant 1 m above ground, the measuring track of the HMMS consisted of a straight line perpendicular to the forest edge, starting in the dense spruce forest and leading 75 m into an open clearing. Tags with bar codes, mounted every metre on the wooden substructure, allowed (a) keeping the speed of the HMMS constant (approx. 0.5 m s−1) and (b) operation of the HMMS in a continuous back and forth running mode. During EGER IOP3, HMMS was operational for almost 250 h. Results show that – due to considerably long response times (between 4 and 20 s) of commercial temperature, humidity and the radiation sensors – true spatial variations of the meteorological quantities could not be adequately captured (mainly at the forest edge). Corresponding dynamical (spatial) errors of the measurement values were corrected on the basis of well-defined individual response times of the sensors and application of a linear correction algorithm. Due to the very short response times (≤ 1 s) of the applied commercial CO2 and O3 analysers, dynamical errors for the trace gas data were negligible and no corrections were done.
41
Hübner, J., J. Olesch, H. Falke, F. X. Meixner, and T. Foken. "A horizontal mobile measuring system for atmospheric quantities." Atmospheric Measurement Techniques Discussions 7, no. 5 (May 7, 2014): 4551–88. http://dx.doi.org/10.5194/amtd-7-4551-2014.
Анотація:
Abstract. A fully automatic Horizontal Mobile Measuring System (HMMS) for atmospheric quantities has been developed. The HMMS is based on the drive mechanism of a garden railway system and can be installed at any location and with any measuring track. In addition to meteorological quantities (temperature, humidity and short/long-wave down/upwelling radiation), HMMS also measures trace gas concentrations (carbon dioxide and ozone). While sufficient spatial resolution is a problem even for measurements on distributed towers, this could be easily achieved with the HMMS, which has been specifically developed to obtain higher information density about horizontal gradients in a heterogeneous forest ecosystem. There, horizontal gradients of meteorological quantities and trace gases could be immense, particularly at the transition from a dense forest to an open clearing, with large impact on meteorological parameters and exchange processes. Consequently, HMMS was firstly applied during EGER IOP3 project (ExchanGE processes in mountainous Regions – Intense Observation Period 3) in the Fichtelgebirge Mountains (SE Germany) during summer 2011. At a constant 1 m above ground, the measuring track of the HMMS consisted of a straight line perpendicular to the forest edge, starting in the dense spruce forest and leading 75 m into an open clearing. Tags with bar codes, mounted every meter on the wooden substructure, allowed (a) keeping the speed of the HMMS constant (approx. 0.5 m s−1) and (b) operation of the HMMS in a continuous back and forth running mode. During EGER IOP3, HMMS was operational for almost 250 h. Results show that – due to considerably long response times (between 4 s and 20 s) of commercial temperature, humidity and the radiation sensors – true spatial variations of the meteorological quantities could not be adequately captured (mainly at the forest edge). Corresponding dynamical (spatial) errors of the measurement values were corrected on the basis of well defined individual response times of the sensors and application of a linear correction algorithm. Due to the very short response times (≤ 1 s) of the applied commercial CO2 and O3 analysers, dynamical errors for the trace gas data were negligible and no corrections were done.
42
Ungermann, J., J. Blank, M. Dick, A. Ebersoldt, F. Friedl-Vallon, A. Giez, T. Guggenmoser, et al. "Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra." Atmospheric Measurement Techniques 8, no. 6 (June 17, 2015): 2473–89. http://dx.doi.org/10.5194/amt-8-2473-2015.
Анотація:
Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 High Altitude LOng Range (HALO) research aircraft during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra that are spectrally sampled every 0.625 cm−1. A total of 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line of sight. Simultaneous in situ observations by the Basic Halo Measurement and Sensor System (BAHAMAS), the Fast In-situ Stratospheric Hygrometer (FISH), an ozone detector named Fairo, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in situ trace gas data, and discrepancies can to a large extent be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.
43
Šimėnas, M., D. Klose, M. Ptak, K. Aidas, M. Mączka, J. Banys, A. Pöppl, and G. Jeschke. "Magnetic excitation and readout of methyl group tunnel coherence." Science Advances 6, no. 18 (May 2020): eaba1517. http://dx.doi.org/10.1126/sciadv.aba1517.
Анотація:
Methyl groups are ubiquitous in synthetic materials and biomolecules. At sufficiently low temperature, they behave as quantum rotors and populate only the rotational ground state. In a symmetric potential, the three localized substates are degenerate and become mixed by the tunnel overlap to delocalized states separated by the tunnel splitting νt. Although νt can be inferred by several techniques, coherent superposition of the tunnel-split states and direct measurement of νt have proven elusive. Here, we show that a nearby electron spin provides a handle on the tunnel transition, allowing for its excitation and readout. Unlike existing dynamical nuclear polarization techniques, our experiment transfers polarization from the electron spin to methyl proton spins with an efficiency that is independent of the magnetic field and does not rely on an unusually large tunnel splitting. Our results also demonstrate control of quantum states despite the lack of an associated transition dipole moment.
44
Ma, S., S. M. Li, and Y. P. Xiong. "Uncertainty Reduced Novelty Detection Approach Applied to Rotating Machinery for Condition Monitoring." Shock and Vibration 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/737213.
Анотація:
Novelty detection has been developed into a state-of-the-art technique to detect abnormal behavior and trigger alarm for in-field machine maintenance. With built-up models of normality, it has been widely applied to several situations with normal supervising dataset such as shaft rotating speed and component temperature available meanwhile in the absence of fault information. However, the research about vibration transmission based novelty detection remains unnoticed until recently. In this paper, vibration transmission measurement on rotor is performed; based on extreme value distributions, thresholds for novelty detection are calculated. In order to further decrease the false alarm rate, both measurement and segmentation uncertainty are considered, as they may affect threshold value and detection correctness heavily. Feasible reduction strategies are proposed and discussed. It is found that the associated multifractal coefficient and Kullback-Leibler Divergence operate well in the uncertainty reduction process. As shown by in situ applications to abnormal rotor with pedestal looseness, it is demonstrated that the abnormal states are detected. The higher specificity value proves the effectiveness of proposed uncertainty reduction method. This paper shows novel achievements of uncertainty reduced novelty detection applied to vibration signal in dynamical system and also sheds lights on its utilization in the field of health monitoring of rotating machinery.
45
Liu, Dan, Tsunetomo Yamada, Cesar Gómez, Vaclav Petricek, Michal Dusek, Ryuji Tamura, Takanobu Hiroto, Guillaume Beutier, Pierre Fertey, and Marc De Boissieu. "Phase transition and atomic structure of Cd6Tb 1/1 approximant to quasicrystal." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C95. http://dx.doi.org/10.1107/s2053273314099045.
Анотація:
We present an in-situ temperature study of the atomic structure of the 1/1 Cd6Tb approximant to an icosahedral quasicrystal. It belongs to the `Tsai' type family of quasicrystal and approximants whose archetype is the well-studied Cd-Yb system[1]. Its high temperature structure can be described as a bcc packing of a large Tsai atomic cluster, whose inner shell is a disordered tetrahedron at room temperature. As for most of the Cd6RE (RE=rare earth) approximant, the Cd6Tb phase undergoes a phase transition at 190 K to a phase of lower symmetry, resulting from an ordering of the inner tetrahedron[2]. Moreover, it has been shown that this phase undergoes a magnetic phase transition below 20 K, with an antiferromagnetic ordering of the Tb moment bearing atoms. It is thus particularly important to have a detailed structural study of this phase. We have carried out a systematic in situ measurement on a single grain from room temperature down to 40K on the crystal beam line located at the Soleil synchrotron. The structural phase transition is observed at about 190K. Using different attenuation, we have collected integrated intensity in a large dynamical range, leading to more than 60000 unique reflections in the C2/c monoclinic low temperature phase. The final wR2 values for room temperature and 40K are equal to 0.0726 and 0.0905 respectively. The resulting atomic structure will be compared to the well-studied approximant Zn6Sc, which is isostructural to Cd6Tb[3]. The ordering of the innermost tetrahedron leads to the distortion of the successive shells. The evolution of the high temperature phase, in particular just above Tc where pretransitional diffuse scattering is observed will be presented.
46
Adams, C., A. E. Bourassa, A. F. Bathgate, C. A. McLinden, N. D. Lloyd, C. Z. Roth, E. J. Llewellyn, et al. "Characterization of Odin-OSIRIS ozone profiles with the SAGE II dataset." Atmospheric Measurement Techniques 6, no. 5 (May 29, 2013): 1447–59. http://dx.doi.org/10.5194/amt-6-1447-2013.
Анотація:
Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) on board the Odin spacecraft has been taking limb-scattered measurements of ozone number density profiles from 2001–present. The Stratospheric Aerosol and Gas Experiment II (SAGE II) took solar occultation measurements of ozone number densities from 1984–2005 and has been used in many studies of long-term ozone trends. We present the characterization of OSIRIS SaskMART v5.0× against the new SAGE II v7.00 ozone profiles for 2001–2005, the period over which these two missions had overlap. This information can be used to merge OSIRIS with SAGE II into a single ozone record from 1984 to the present, if other satellite ozone measurements are included to account for gaps in the OSIRIS dataset in the winter hemisphere. Coincident measurement pairs were selected for ±1 h, ±1° latitude, and ±500 km. The absolute value of the resulting mean relative difference profile is <5% for 13.5–54.5 km and <3% for 24.5–53.5 km. Correlation coefficients R > 0.9 were calculated for 13.5–49.5 km, demonstrating excellent overall agreement between the two datasets. Coincidence criteria were relaxed to maximize the number of measurement pairs and the conditions under which measurements were taken. With the broad coincidence criteria, good agreement (< 5%) was observed under most conditions for 20.5–40.5 km. However, mean relative differences do exceed 5% for several cases. Above 50 km, differences between OSIRIS and SAGE II are partly attributed to the diurnal variation of ozone. OSIRIS data are biased high compared with SAGE II at 22.5 km, particularly at high latitudes. Dynamical coincidence criteria, using derived meteorological products, were also tested and yielded similar overall results, with slight improvements to the correlation at high latitudes. The OSIRIS optics temperature is low (<16 °C) during May–July, when the satellite enters the Earth's shadow for part of its orbit. During this period, OSIRIS measurements are biased low by 5–12% for 27.5–38.5 km. Biases between OSIRIS ascending node (northward equatorial crossing time ~18:00 LT – local time) and descending node (southward equatorial crossing time ~06:00 LT) measurements are also noted under some conditions. This work demonstrates that OSIRIS and SAGE II have excellent overall agreement and characterizes the biases between these datasets.
47
Tschanz, B., C. Straub, D. Scheiben, K. A. Walker, G. P. Stiller, and N. Kämpfer. "Validation of middle-atmospheric campaign-based water vapour measured by the ground-based microwave radiometer MIAWARA-C." Atmospheric Measurement Techniques 6, no. 7 (July 23, 2013): 1725–45. http://dx.doi.org/10.5194/amt-6-1725-2013.
Анотація:
Abstract. Middle atmospheric water vapour can be used as a tracer for dynamical processes. It is mainly measured by satellite instruments and ground-based microwave radiometers. Ground-based instruments capable of measuring middle-atmospheric water vapour are sparse but valuable as they complement satellite measurements, are relatively easy to maintain and have a long lifetime. MIAWARA-C is a ground-based microwave radiometer for middle-atmospheric water vapour designed for use on measurement campaigns for both atmospheric case studies and instrument intercomparisons. MIAWARA-C's retrieval version 1.1 (v1.1) is set up in a such way as to provide a consistent data set even if the instrument is operated from different locations on a campaign basis. The sensitive altitude range for v1.1 extends from 4 hPa (37 km) to 0.017 hPa (75 km). For v1.1 the estimated systematic error is approximately 10% for all altitudes. At lower altitudes it is dominated by uncertainties in the calibration, with altitude the influence of spectroscopic and temperature uncertainties increases. The estimated random error increases with altitude from 5 to 25%. MIAWARA-C measures two polarisations of the incident radiation in separate receiver channels, and can therefore provide two measurements of the same air mass with independent instrumental noise. The standard deviation of the difference between the profiles obtained from the two polarisations is in excellent agreement with the estimated random measurement error of v1.1. In this paper, the quality of v1.1 data is assessed for measurements obtained at two different locations: (1) a total of 25 months of measurements in the Arctic (Sodankylä, 67.37° N, 26.63° E) and (2) nine months of measurements at mid-latitudes (Zimmerwald, 46.88° N, 7.46° E). For both locations MIAWARA-C's profiles are compared to measurements from the satellite experiments Aura MLS and MIPAS. In addition, comparisons to ACE-FTS and SOFIE are presented for the Arctic and to the ground-based radiometer MIAWARA for the mid-latitude campaigns. In general, all intercomparisons show high correlation coefficients, confirming the ability of MIAWARA-C to monitor temporal variations of the order of days. The biases are generally below 13% and within the estimated systematic uncertainty of MIAWARA-C. No consistent wet or dry bias is identified for MIAWARA-C. In addition, comparisons to the reference instruments indicate the estimated random error of v1.1 to be a realistic measure of the random variation on the retrieved profile between 45 and 70 km.
48
Wendisch, Manfred, Andreas Macke, André Ehrlich, Christof Lüpkes, Mario Mech, Dmitry Chechin, Klaus Dethloff, et al. "The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification." Bulletin of the American Meteorological Society 100, no. 5 (May 2019): 841–71. http://dx.doi.org/10.1175/bams-d-18-0072.1.
Анотація:
AbstractClouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.
49
Liu, Jingxin, Zhihui Zhang, Qingguo Xie, and Wenzhong Liu. "Nonlinear dynamic thermometry: Temperature measurement using immobilized magnetic nanoparticles." Journal of Applied Physics 131, no. 17 (May 7, 2022): 173901. http://dx.doi.org/10.1063/5.0090240.
Анотація:
We present a new method for measuring the temperature of magnetic nanoparticles that can also be adapted to immobilized particles. The Néel relaxation mechanism, which dominates the dynamic magnetization process of immobilized magnetic nanoparticles, can be used as an intermediate parameter in a sensing model to obtain temperature information. In this paper, we use the nonlinear response properties of magnetic nanoparticles to derive an analytical expression for the relationship between the phase of cubic susceptibility and temperature. We also consider dipole–dipole interactions and the dependence on field amplitude. Under experimental conditions at selected frequencies and field amplitudes, we compare temperature measurements of magnetic nanoparticles obtained with the proposed thermometry model with those obtained from existing nonlinear dielectric relaxation models. The results show that the temperature measurements obtained from the proposed model are closer to the reference temperatures in the temperature range of 308–353 K, with a standard deviation of less than 0.1 K in the temperature measurement. This new method successfully applies the nonlinear properties of magnetic nanoparticles to high-precision dynamic temperature measurements. It extends the applicability range of temperature measurement methods to conditions with strong interactions or large ac field amplitudes. This new method is expected to be applicable in anti-magnetic environments, for example, in biochemical temperature measurements of magnetically labeled cells in vivo.
50
Xu, Mengyang, Deepu George, Ralph Jimenez, and Andrea Markelz. "Photo-Switching of Protein Dynamical Collectivity." Photonics 8, no. 8 (July 29, 2021): 302. http://dx.doi.org/10.3390/photonics8080302.
Анотація:
We examine changes in the picosecond structural dynamics with irreversible photobleaching of red fluorescent proteins (RFP) mCherry, mOrange2 and TagRFP-T. Measurements of the protein dynamical transition using terahertz time-domain spectroscopy show in all cases an increase in the turn-on temperature in the bleached state. The result is surprising given that there is little change in the protein surface, and thus, the solvent dynamics held responsible for the transition should not change. A spectral analysis of the measurements guided by quasiharmonic calculations of the protein absorbance reveals that indeed the solvent dynamical turn-on temperature is independent of the thermal stability/photostate however the protein dynamical turn-on temperature shifts to higher temperatures. This is the first demonstration of switching the protein dynamical turn-on temperature with protein functional state. The observed shift in protein dynamical turn-on temperature relative to the solvent indicates an increase in the required mobile waters necessary for the protein picosecond motions, that is, these motions are more collective. Melting-point measurements reveal that the photobleached state is more thermally stable, and structural analysis of related RFP’s shows that there is an increase in internal water channels as well as a more uniform atomic root mean squared displacement. These observations are consistent with previous suggestions that water channels form with extended light excitation providing O2 access to the chromophore and subsequent fluorescence loss. We report that these same channels increase internal coupling enhancing thermal stability and collectivity of the picosecond protein motions. The terahertz spectroscopic characterization of the protein and solvent dynamical onsets can be applied generally to measure changes in collectivity of protein motions.