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1
Kallos, George B. "Flow dynamics and stability in severe rainbands." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/25735.
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Kirkland, Jessica Lynn. "Regional Differences in the Spatial Patterns of Precipitation Bands in Hurricanes Through Landfall along the Gulf of Mexico and Atlantic Coasts of the United States." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/96586.
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Evolutionary periods of precipitation distribution in tropical cyclones (TCs) are sometimes misrepresented in numerical weather prediction models due to the rapid nature of TC structure changes that accompany intensity change. To better understand quantitative changes in TC rainband structure around landfall, I quantify the spatial distribution of precipitation in 62 landfalling TCs along the Gulf of Mexico and Atlantic coasts of the U.S. between 1998 and 2014. The Tropical Rainfall Measuring Mission (TRMM) 3B42 product is utilized to assess three spatial measures of precipitation: 1) area, 2) closure, and 3) dispersion. Calculations are made using two rain rate thresholds, 0.254mm/hr and 5mm/hr, to capture and compare changes in light and heavy precipitation, respectively. Changes in TC precipitation are statistically different based on landfall location along the Atlantic vs. Gulf. Overall, dispersion (measure of centrality) is the most dissimilar metric due to variability between 0.254mm/hr and 5mm/hr results. Lighter precipitation decreases in area and expands away from the TC center, while heavier precipitation contracts rather than disperses in Gulf landfalling storms. A k-means clustering produces six landfall regions and reinforces the result of heavier precipitation becoming more central along the Gulf, while Atlantic landfalling storms exhibit decreased centrality. Significant differences were not found in storms that undergo extratropical transition or dissipate later in lifecycle. The holistic approach exhibited by this study reveals wide variability among a large dataset of storms making landfall; therefore, sub-setting techniques are helpful to hurricane forecasters in understanding the role of landfall location.<br>MS
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Judt, Falko. "Convectively-Generated Potential Vorticity in Rainbands and Secondary Eyewall Formation in Hurricanes." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/214.
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Concentric eyewall formation and eyewall replacement cycles are intrinsic processes that determine the intensity of a tropical cyclone, as opposed to purely environmental factors such as wind shear or the ocean heat content. Although extensive research has been done in this area, there is not a single widely accepted theory on the formation of secondary eyewall structures. Many previous studies focused on dynamic processes in the inner core of a tropical cyclone that would precede and ultimately lead to the formation of a secondary eyewall. Hurricanes Katrina and Rita in 2005 were frequently sampled by research aircraft which gathered a copious amount of data. During this time, Rita developed a secondary eyewall which eventually replaced the original eyewall. This thesis will investigate the formation of a secondary eyewall with particular emphasis on the rainband region, as observations show that an outer principal rainband transformed into the secondary ring. A high resolution, full physics model (MM5) initialized with global model forecast fields correctly predicted the secondary eyewall formation in Rita. The model output will be used to investigate both Katrina and Rita in terms of their PV generation characteristics since PV and vorticity maxima correlate well with wind maxima that accompany the eyewall and rainbands. Furthermore, dynamical processes such as vortex Rossby wave (VRW) activity in the inner core region will be analyzed. Comparison of the differences in the two storms might shed some light on dynamics that can lead to structure changes. Comparison of the model data with aircraft observation is used to validate the results. Doppler radar derived wind fields will be used to calculate the vertical vorticity. The vorticity field is closely related to PV and thus a manifestation of the PV generation process in the rainband. The investigation has shown that Rita?s principal rainband features higher PV generation rates at radii beyond 80 km. Both the azimuthal component and the projection of asymmetric PV generated by convection onto the azimuthal mean connected with the principal band are hypothesized to be of importance for the formation of the secondary eyewall. VRW were found not to be important for the initial formation of the ring but might enhance convective activity once the outer eyewall contracts.
4
Chen, Yongsheng 1973. "On the dynamics of the inner spiral rainbands in a simulated hurricane." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82843.
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Despite the fact that spiral rainbands have long been detected in radar observations, many aspects of their dynamics and their role in hurricanes still remain unresolved. In this thesis, the high-resolution PSU-NCAR nonhydrostatic mesoscale model (MM5) is used to perform three numerical simulations, namely, the control run, the dry run and the landfall simulation. The dynamics of inner spiral rainbands formed in the simulated hurricanes are studied.<br>It is shown that the interaction of low-level potential vorticity (PV) anomalies with boundary layer friction and the strong coupling of the PV band and the cloud band give rise to the inner spiral rainbands. The propagation properties of the PV bands are analyzed and found to be consistent with predictions of vortex Rossby wave theory. Empirical normal mode method is further applied to separate the vortex Rossby waves from the gravity waves. The former dominates the latter in terms of wave activities. The radial and vertical propagation and the associated eddy momentum and eddy heat fluxes of vortex Rossby waves are studied using the Eliassen-Palm (EP) flux. The wave-mean-flow interaction indicated by the divergence of the EP flux shows significant effects on the intensification of the hurricanes.<br>While diabatic heating tends to maintain a ring structure of PV by continually generating high PV in the eyewall, the vortex Rossby waves tend to redistribute the PV in the ring and to increase the inner-core PV. When diabatic heating is suppressed in the dry run and in the landfall simulation, the PV ring evolves to monopolar structure. The dynamical properties of the inner spiral rainbands and their roles on the intensity then vary as a response to the evolving mean PV structure of the hurricane. Nevertheless, the total effect of the asymmetric diabatic heating and the vortex Rossby waves tends to counteract the effect of the mean circulation.
5
Umemoto, Yasuko. "Studies on orographic rainbands based on combined wind profiler-weather radar observations." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136773.
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Robe, Françoise R. (Françoise Romain). "Sea, sun, and shear : a recipe for precipitating convection, tropical rainbands, and hurricane spiral arms." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/17416.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.<br>Includes bibliographical references (p. 235-242).<br>by Françoise R. Robe.<br>Ph.D.
7
Norris, Jesse Michael. "Dynamics and organisation of precipitation bands in the midlatitudes." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/dynamics-and-organisation-of-precipitation-bands-in-the-midlatitudes(b9d8f4e8-ec91-43f2-b3e1-936e2a1995b5).html.
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The thesis is presented in alternative format, meaning that the results of the thesis take the form of three journal articles, each telling a distinct story within the subject matter, but collectively highlighting the sensitivity of bands to frictional and diabatic processes. Paper 1 is an idealised-modelling study with the Weather Research and Forecasting (WRF) model, in which moist baroclinic waves are simulated from an initial zonally uniform mid-latitude jet on an f-plane at 20-km grid spacing, and the sensitivity of the resulting precipitation bands is explored. Paper 2 employs further WRF idealised-baroclinic-wave simulations and takes a simulation from Paper 1, after the cold front has formed, as the initial condition. A nested domain at 4-km grid spacing is inserted when this simulation is re-initialised to invesigate the sensitivity of finer-scale precipitation cores along the surface cold front. In both Papers 1 and 2, friction and latent-heat release enhance multiple banding at the two distinct horizontal scales, while surface fluxes hinder multiple banding. Paper 3 studies post-frontal snowbands over the English Channel and Irish Sea during extreme cold-air outbreaks in the winters of 2009-10 and 2010-11, via a climatology of precipitation-radar, sounding, and SST data, and real-data WRF sensitivity simulations of one such band over the English Channel. The observational and modelling results show that strong winds and large differential heat fluxes between land and sea were necessary to generate banded precipitation. Coastal orography and the land-sea frictional contrast aided the morphology of bands, but banded precipitation did still form in the absence of these influences in the sensitivity simulations. These three studies and the thesis as a whole highlight the role of frictional and diabatic processes in modifying various types of precipitation bands within baroclinic waves, and in generating bands that would otherwise not exist.
8
Valton, Anne-Marie. "Cloud dynamics-pollutant interactions in a rainband." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65932.
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Pitre, John Stephen. "The role of oxidation in the chemistry of a rainband /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66087.
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Andrew, Giles. "The influence of the ice phase on the simulated chemistry of a rainband /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63867.
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Macdonald, Anne Marie. "Sulphur dioxide oxidation in a rainband : effects of in-cloud hydrogen peroxide production." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55616.
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Updike, Aaron Jeffrey. "A Modeling Study of the Principal Rainband in Hurricane Matthew (2016) and the Influence of Remote Terrain on Hurricane Structure During its Intensification in the Southern Caribbean." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90391.
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Hurricane Matthew (2016) was a category 5 hurricane that interacted with remote terrain over northern South America in the early stages of its life cycle. Because tropical cyclone (TC) precipitation and convection are known to be crucial factors in the understanding and forecasting of TC intensity, this study investigates how this terrain impacted Hurricane Matthew's rainband structure. Remote terrain is hypothesized to play a role in the strength of TC rainband convection by modifying the thermodynamic environment such that subsiding dry air advects over an extremely moist ocean surface layer leading to increased moist static instability. To investigate this hypothesis, this study utilizes the Advanced Research Weather and Research Forecasting Model (WRF-ARW) to create a high-resolution (2-km horizontal grid spacing) control simulation (CTL) of Hurricane Matthew and a second experimental simulation with a 50% reduction of terrain height over the topography of northern South America (T50). This study focuses on a particular convective rainband positioned downstream of the terrain that displayed prolonged robust convection during the initial stages of Hurricane Matthew's life cycle. Results indicate that characteristics of this robust rainband are consistent with prior research on an inner core rainband called a principal rainband. This rainband does not display differences in intensity in the two simulations but is located closer to the TC center and more persistent in the control simulation. In the region downstream of the topography, significantly (p < 0.05) drier conditions exist in the control simulation, which is consistent with the hypothesis that downslope motion would lead to a drier air mass. TC structural changes are also apparent, with a weaker TC in the reduced topography simulation. This research emphasizes the potentially important role of terrain distant from the TC center with possible influences on TC rainband convection and warm core structure. Conclusions of this research are limited due to the small sample size of a single case study. An ensemble modeling study and additional cases are needed for a more thorough conclusion on the impact of remote terrain on TC structure.<br>Master of Science<br>Predicting the intensity of hurricanes remains a monumental challenge for hurricane forecasters. Many factors can influence the intensity of hurricanes, including the strength, frequency, and spatial distribution of hurricane rainbands (band of precipitation). The hypothesis for this study is that terrain distant from the hurricane center can alter the hurricane environment and cause more frequent and stronger rainbands to form. To assess this hypothesis, I use a weather model to simulate Hurricane Matthew (2016) while it was interacting with remote terrain over northern South America on September 30 - October 1, 2016. Then I use the same model, but with terrain height reduced by 50% over northern South America and analyze the similarities and differences in the hurricane structure and rainband patterns. The results of this study suggest that terrain did not alter the peak rain rates in the hurricane rainbands but may have caused more frequent, widespread, and prolonged precipitation. Also, differences in hurricane structure were apparent when comparing the two model simulations. The reduced terrain simulation produced a weaker hurricane, lending some evidence to support the hypothesis that terrain may have played a role in altering the hurricane structure. These results demonstrate the potential importance of distant terrain on forecasting hurricane precipitation and intensity.
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Chen, Ying, and 陳瀅. "Study on Surface Features of Typhoon Rainbands." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/05492999630321581905.
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Luo, Jhang-Shuo, and 羅章碩. "Analysis of tropical cyclone rainbands in outer environment." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/98ks5e.
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Lee, Chun-Yen, and 李俊彥. "Perturbation Pressure in Cells of Rainbands Associated With Typhoon Morakot." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/20870906216948791169.
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碩士<br>國立臺灣大學<br>大氣科學研究所<br>101<br>This thesis studies the convective cell interaction with the low-level jet in the typhoon (TY) environment. Observations of TY Morakot (2009) indicate that the east-west oriented rainband in the Taiwan Strait is in the convergent zone caused by the interaction of the TY circulation and the southwesterly monsoon flow. The rainband is with low-level westerly jet of 30 m/s and composed of many eastward moving convective cells. The new convection often developed to the west of the mature cells and the eastward speed of the convective cell in general is slower than the low-level jet speed. We use 1-km resolution Cloud Resolving Storm Simulator (CReSS) model to simulate and to analyze the convective cells in rainbands associated with TY Morakot. Our hypothesis that the vertical wind shear associated with the low level jet, when interacted with the horizontal vertical wind variation in the presence of the convection, can generate significant vertical pressure gradient force on the upwind side of the convective cell. The vertical pressure gradient force to the west of the convective cells may strengthen the convective cell in the TY Morakot rainband.
With the numerical model data, we solve for the buoyancy pressure perturbation and dynamic pressure perturbation. The dynamic pressure perturbation can be further separated into the linear and non-linear contributions. The linear term mainly involves the product of the vertical wind shear from the low-level jet and the horizontal variation of the convective updraft and the nonlinear terms are from convective cells. Our pressure diagnosis suggests that the linear contribution is the most important in the dynamic pressure perturbation. The interaction of the low-level jet with convection will produce relative high (low) dynamic pressure perturbation in the lower (upper) level and positive vertical perturbation pressure gradient to the west of the convective cells. Together with the buoyancy, the dynamics vertical pressure perturbation gradient force also contributes to the positive vertical acceleration to the west of the mature convective cells.
Our analysis highlights the importance of the low-level jet in TY environment when interact with existing convective cells may produce significant dynamic vertical pressure perturbation gradient to the upwind side. The dynamic vertical pressure gradient force may strengthen the convective cells in the TY rainband.
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Luo, Hong Kai, and 駱鴻愷. "Frontal Rainbands and Low Level Jet in Mei-Yu Seasons." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/27836228433832992907.
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Chen, Wen-Hsuan, and 陳文軒. "Dual-Doppler Analysis of Outer Rainbands Associated with Typhoon Haitang (2005)." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/66986243659270425257.
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Tsai, Chia-Lun, and 蔡嘉倫. "Observational study of structures and surface fluctuations of typhoon rainbands of Longwang (2005)." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/90959255717779611939.
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Chu, Shiou-Rong, and 朱琇榕. "Kinematic and Microphysical Properties of Typhoon Rainbands Observed by Polarimetric Radar in Taiwan." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/hwp48g.
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碩士<br>國立臺灣大學<br>大氣科學研究所<br>106<br>Typhoon Soudelor (201513) made landfall and moved across the topography in northern Taiwan. The Convective-Stratiform Separation Algorithm were used to identify two secondary rainbands (“rainband N” and “rainband S”) located in the right front quadrant during Soudelor’s landfall. The evolution, kinematic and microphysical characteristics of these rainbands are examined in this study.
The rainband kinematic structures were examined using dual-Doppler retrieved winds. The reflectivity and band-relative horizontal winds of two rainbands seem to suggest they were in different developing stages: rainband S was intensifying with convergence below and divergence above while rainband N was dissipating with divergence below and convergence above. The line-averaged vertical airflow and precipitation structure associated with the offshore segments of two rainbands exhibit some similar features to inner rainbands while some resemble outer rainbands. Consistent with the kinematic structures, the polarimetric vertical profiles reveal corresponding microphysics in two rainbands. The vertical profiles of polarimetric variables in rainband S indicate more moisture content was transported to the higher level through the intensifying updraft, which caused greater supersaturation for ice particles to grow above the melting layer. The features below the melting layer suggest collision-coalescence process and/or accretion of cloud water by raindrops. Although the polarimetric vertical profiles of rainband N have similar distributions, the values are all smaller than that in rainband S. This might be related to the dissipating of rainband N. The microphysics suggest both ice-phased and warm rain process play important roles in the major pathway to heavy rainfall in rainbands when they were offshore.
After two rainbands made landfall, the reflectivity structures at near-ground level became stronger. The polarimetric features also suggest the mean raindrop size and liquid water content are the largest, which relates closely to heavier rainfall within the rainbands due to the terrain lifting. However, at later time spans, rainband N was observed mostly dissipated. This might be related to the intensification that original downward motion combines with the downslope flow in the lee. In contrast, the reflectivity structure and airflow pattern in rainband S associated with the landfalling segment are similar to that with the offshore segment, but with weakening updrafts. The features of polarimetric variable above the melting layer presented less curved profiles, indicating the less moisture content transported for ice-phased processes. Therefore, the dominated process to the precipitation after two rainbands made landfall is mainly via warm-rain processes like collision and coalescence.
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Chen, Buo-Fu, and 陳柏孚. "Long-lasting rainbands associated with the interactions between tropical cyclones and their environment." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/89769281591975999401.
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博士<br>國立臺灣大學<br>大氣科學研究所<br>103<br>This study analyzes two types of long-lasting rainbands associated with tropical cyclones (TCs) in the western North Pacific. These rainbands are separated from the eyewall convection and form due to the interactions of TCs and the monsoonal environments. The first type is the outer mesoscale convective system (OMCS), which is a linear convective system with a large cold cloud shield that develops from the TC distant rainband (e.g. OMCS embedded in Typhoon Morakot 2009). The second type is the enhanced rainband (ERB) that develops from TC principal rainband and is accompanied with active and long-lasting convections. A total of 109 OMCSs and 90 ERBs that occurred in the western North Pacific during 1999-2009 are identified using infrared and passive microwave images. About 22% (21%) of all TCs have at least one OMCS (ERB) during their life cycle. Eighty five OMCSs and 80 ERBs that developed in the southern part of TC are further analyzed. Results show that the south-type OMCSs developed at 200-700 km radii from the TC center and moved predominantly outward. The south-type ERBs developed at 100-300 km radii from the TC center and moved predominantly cyclonically. The TC intensification rate decreased but the rate of TC size change did not change when after an OMCS was present. However, the TC size increased significantly after an ERB was present. Seventy percent of very large typhoons (radius of 15 ms-1 wind > 3.6°) had an ERB during the period when they intensified from tropical storms to typhoons.
The Weather Research and Forecasting (WRF) model was used to simulate the development and maintenance of an OMCS that occurred to the southwest of Typhoon Fengshen (2008). Results show that the WRF does a reasonably-well simulation except that the OMCS is shifted southward by 100 km because the simulated TC outer circulation is larger. The low-level TC circulation of Frngshen is deflected by the Luzon terrain causing a westward shift of an elongated north-south moisture band which then converges with the low level monsoon southwesterly flows. As a result, the OMCS develops at the outer region of Fengshen instead of being spiraled into the inner-core region. The formation of this moisture band is attributed to i) the moisture from the southwest monsoon that is transported cyclonically around the TC center, and ii) the tilting of the TC due to the strong northeasterly vertical wind shear (VWS). The TC-VWS interactions result in down-shear frictional convergence associated with asymmetric vorticity in the boundary layer and the formation of the moisture band. The OMCS develops when this moisture band interacts with the low-level southwesterly flow. Results also show that a characteristic structure of rear-fed inflow with leading stratiform in the cross-line direction (toward the south) is established when the OMCS becomes mature and moves southward. Such a structure contributes to the long duration of the OMCS because the high-CAPE air in the moisture band keeps feeding into the system and new cells form continuously at the trailing (north) edge of a cold pool (Δθ < - 3K) associated with the large stratiform precipitation. The synoptic conditions of all 85 south-type OMCS formations are examined. Results show that 51% of these OMCSs that formed at the intersection of an elongated moisture band in the TC northerly circulation and the southwest monsoon flow have similar feature with that of the OMCS embedded in Fengshen.
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Huang, Yu-Jui, and 黃宇睿. "Roles of Interactions of Typhoon Nesat (2017) and Haitang (2017) in the Formation and Structure of Outer Tropical Cyclone Rainbands." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/awr3fh.
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碩士<br>國立臺灣大學<br>大氣科學研究所<br>107<br>Outside the eyewall, tropical cyclone rainbands (TCRs) are the most striking and threatening region, causing not only heavy precipitation but intense winds. When Typhoon Nesat (2017) and Haitang (2017) were located near Taiwan, outer TCRs oriented approximately normal to the coast were initiated off the southwestern coast of Taiwan and resulted in the severe flood over the coastal and inland regions. Thus, it is crucial to understand the formative mechanism of the studied TCRs. This study used ground-based dual-Doppler and surface observations and NCEP-CFS reanalysis data to document the structural feature of the outer TCRs. The multiple-Doppler-derived wind fields showed that the formation of the TCRs was related to the low-level convergence between the southwesterly flow and the northwesterly flow. According to the budget analysis of radial momentum equations, the southwesterly flow was more subgradient due to the interaction of Typhoon circulations associated with Nesat and Haitang. In contrast, the northwesterly flow that was dominated by the outer circulation of Typhoon Nesat was close to the gradient wind balance. In addition, the structure of the outer TCRs in the nearshore region is different from that seen in the offshore region, which was caused by more pronounced low-level convergence produced as the coastally blocked flow (south-southwesterly flow) that occurred under low Froude number regime encountered the northwesterly flow.
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CHUANG, YAO-CHUNG, and 莊耀中. "Convective Rainband Structure of Typhoon Morakot(2009)." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/22982446891070330532.
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博士<br>國防大學理工學院<br>國防科學研究所<br>104<br>The research uses the Air Force weather wing C-band dual-polarization radar in Makung and the Central Weather Bureau S-band Doppler weather radar in Qigu to observe the rainbands of typhoon Morakot, and further analyze on the kinematic structure of convective cells in the rainbands of typhoon by using the Dual-Doppler wind analysis to understand the development of strong convective cell evolution.
The case of this study focuses on rainbands developed during the period from 2200 UTC on 08 August 2009 to 0600 UTC on 09 August 2009. The distance between rainbands and the center of typhoon were probably two hundred fifty kilometers. Besides, the rainbands were more intense than the other rainbands ehPaedded within the typhoon. The rainbands have linear characteristics different from spiral rainbands. The location of rainbands was covered by the scanning range of both radars, providing good opportunity for Dual-Doppler wind synthesis.
The synthesis wind field delineated that a significant confluent zone superimposed on the convective rainband. The confluent zone was combined by the westerly and southwesterly flow. It is well pronounced that new cells developed at the upstream of the confluence, and propagated inland westward. This confluence might enhanced the westerly flow with maximum velocity over 24 ms-1, which could be referred as a jet and resehPaled the second horizontal wind maximum (SHWM) through the associated rainband was dissimilar to the spiral band. The intense westerly extended from 2 to 5 km in height. The mature convective cell and updraft existed at the northern side of the strong wind, leaning to the inward side of typhoon.
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Tsai, De-Iou, and 蔡德攸. "An analysis of spiral rainband accompanied with typhoon." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/77262266670319864612.
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Wijesekera, Hemantha. "Diagnostic modeling study of a severe narrow cold-frontal rainband." Thesis, 1986. http://hdl.handle.net/1957/29292.
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A diagnostic modeling study of the cloud and precipitation
processes, and also frontogenesis have been analyzed in a severe
narrow cold-frontal rainband with the aid of a three-dimensional,
diagnostic cloud model.
The results of the model simulations indicate that the heavy
precipitation just behind the surface cold front was associated
with a low-level warm rain process driven by the severe prefrontal
updraft. The precipitation well behind the leading edge of cold
front resulted from the melting of graupel. The sensitivity
studies for the rain water distribution indicated that the
Analytical Gamma distribution may be a more suitable functional fit
for the raindrop distribution as compared with the Marshall-Palmer
distribution.
The differential heating due to microphysical processes
(condensation and evaporation) at the leading edge of the surface
cold frontal region facilitated the required density contrast
across the front and thus maintained the propagation of the density
current. The leading edge of the cold front was also characterized
by frontogenesis for levels above 0.9 kin and frontolysis just ahead
and immediately behind the cold front. The low level frontolysis
indicated that buoyancy effects were almost negligible at the
leading edge of the cold front. Instead the upward motion was
created by mechanical lifting (pressure effects). The frontogenetical
effects due to diabatic heating were quite important at
the 1.2 - 2 km levels where the peak updraft occurred.<br>Graduation date: 1987
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PAN, CHIU-YIN, and 潘秋吟. "The geographic effect on longliving Mei-Yu frontal rainband in subtropical." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/09943097861980793762.
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碩士<br>國立中央大學<br>大氣物理研究所<br>85<br>IOP13為TAMEX期間較為特殊的案例，其生命期長達二十幾個小時，為了
要研究其緩慢移動及長生命期的特徵和在登陸後能持續發展的原因，在本
文中將以多個連續時間的回波分析來探討雨帶及風場水平結構的演變、雨
帶及風場結構的分佈、及以在追隨地勢座標計算其三維的風場來探討地形
對回波分佈的影響。由6月25日0747~1036LST約3小時每隔7分鐘一組連續
時間徑向風場及回波圖分析，可知此雨帶系統移動相當緩慢，且在此期間
回波強度變化不大。後緣雨帶及新生胞的併入對主回波區的維持及加強有
不容忽視的重要性。地形的作用使風切線的走向由東北－西南走向逐漸變
成風切線的北端更偏南-北走向而其南端則偏東北東-西南西走向。其亦使
整個回波型態更複雜化，回波區的結構由主回波區的東北－西南走向逐漸
轉變成東－西走向及沿地形的南－北走向。由0823~0839LST不同高度的的
回波和合成風場分析可知在低層西風與西南風形成一明顯的風切線，愈往
高層風向愈偏北，風切線隨著高度往東南方向傾斜，中高層以西風、西北
風及北風為主且高層已無風切線存在。由不同高度的回波結構分佈分析結
果來看，主回波區位於風切線的前緣，受到中高層垂直風切的影響使得強
回波中心愈往高層愈往東南方向傾斜，主回波區的對流發展可至15km高，
低層的回波受地形的阻擋作用而局限於地形的西側。以追隨地勢座標
由0823~0839LST所得到的回波和合成風場分析來探討地形對雨帶的影響並
與CEDRIC軟體所得到的結果比較，在地形處由追隨地勢座標下所得到的三
維風場較CEDRIC軟體所得到的結果佳。結果顯示低層的入流以西南風及西
風為主，至中高層主要的入流則以西風及西北風為主。地形的抬升作用使
低層西南氣流的水氣可往上傳輸至中層，當低層的水汽供應與中層的輻合
配合的當時，可增強垂直速度且回波可垂直發展的很高。
26
Tang, Yu-shuang, and 唐玉霜. "The mesoscale characteristics of rainband from radar analyses: typhoon Morakot(2009)." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/30670362286469587180.
Full textAbstract:
碩士<br>國立中央大學<br>大氣物理研究所<br>98<br>On August 8, 2009, a few strong west-east oriented rain bands associated with Typhoon Morakot formed in southwestern Taiwan. Many deep convection cells were embedded in these rain bands and moved toward the island very quickly. We carried out dual-doppler analysis of Chigu and Magung to retrieve 3-D wind field from 0954 to 1031UTC. The 3-D synthesis wind field revealed that the typhoon northwest wind circulation in Taiwan Strait encountered the southwestern flow to cause a strong convergence zone and form the rain band. The three dimensional reflectivity and flow structures are similar to the conceptual model of hurricane rain band. A low level jet (>30m/s) 10-30km wide, length >100km associated with this rain band.
The hot tower embedded in the rain band is defined by a threshold of reflectivity (dBZ >25) at 10 km height, and compare the features of the hot towers in different stage (1809LST and 1831UTC). The reflectivity pattern was slightly tilting southward and the reflectivity contour of 25dBZ reached 15km. The updraft of the hot tower was near 20m/s. When the cell moved along the rain band, the cell usually accompanied with the meso-γ-scale jet streak (>40m/s, 2-3km width, 5-20km length) and the positive vertical vorticity. Through the vorticity budget, we found the updraft play an important role to enhance the vertical vorticity and the strong jet streak. Along the jet many deep convection cells (hot towers) were moving quickly. Because the jet was blocked by the mountains in southern Taiwan, the sloping updrafts were enhanced to induce heavy rainfall. The prolonged stay of this devastating rain band caused the high accumulation of rain.
We analyzed the distributions of the polarimetric parameters from Magong radar to reveal microphysical structure in the hot tower. The results show that many little supercool drops were carried by the strong updraft into the tower. The low ZDR and KDP indicated the ice particles in the upper level of tower. The lower ρHV proved the mixed phase near 7-9 km height. After compared the hot towers between typhoon Morakot (2009) and typhoon Sinlaku (2008), the former not only had deeper and stronger convection, but also had larger number of raindrops. The huge amount latent heat was released in whole tower, and through cloud dynamic mechanism, it was helpful for maintaining lifetime of hot tower and low level jet.
27
Tien, Angel, and 田安琪. "Diagnostic Analysis of A Long-Lived Rainband in TAMEX IOP-13." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/37495594079068152522.
Full textAbstract:
碩士<br>國立中央大學<br>大氣物理研究所<br>81<br>IOP#13是梅雨個案之中較特殊的例子，因為它的雨帶存在長達二十小時以
上，帶來了大量雨水，並且在此期間曾觀察到兩次雨帶明顯旋轉的現象，
這種旋轉特性可能有助於雨帶維持其生命，本文因此欲從渦度的觀點來解
釋此個案長命的原因。 @ 本文分成以下四個階段說明雨帶的旋轉性有
助於其生命的維持： (1)討論渦度收支，說明各收支項對渦度變化的影
響。(2)討論渦度場分佈與壓力場間的關係。(3)討論垂直壓力梯度力與垂
直速度的關係。 (4)討論渦度的穩定性，並說明垂直速度與渦度間相互回
饋的效果，是本個案長命的原因。分析結果顯示，在中層，平流效應和浮
力效應對渦度的貢獻為反效果，因此合效應使得渦度的變化很小，幾乎維
持在同樣的強度；在上層，是平流效應、浮力效應和傾側效應相抗衡的情
況，亦會使得渦度的變化很小。而浮力效應來自中層水汽凝結潛熱釋放，
傾側效應是因水平渦管被在水平方向上逐漸增加的垂直速度在上層傾斜成
垂直渦管而來。比較各層的渦度，發現中上層渦度較低層強，表示此處的
壓力小，且在九公里高度左右有一低壓中心，這個低壓中心可以加速引進
來自低層西側的暖空氣，造成降雨。此外，這樣的壓力場配置使得低層到
中層皆為負壓力梯度力，即垂直上升速度加速區。前述的機制維持了上升
氣流的強度和位置。此外，因為渦度的分佈沒有很大的變化(暗示渦度收
支的情況亦變化不大)，垂直速度的分佈(指上升氣流區和下降氣流區)也
不會有太大的變化，這使得垂直速度的水平梯度維持穩定，再配合變化不
顯著的環境風切，這便又是穩定的水平渦度了。如此周而復始，垂直速度
始終保持一定的強度，使得IOP#13得以長命。
28
蘇南州. "A numerical study on rainband structure and evolution of Typhoon Hagupit (2008)." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/wuuj5h.
Full text
29
Yi-SHeng, Chen, and 陳益盛. "The Characteristics of the Linear Echo Wave Pattern embedded within the Typhoon Rainband." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/35276814378818805737.
Full textAbstract:
碩士<br>國防大學理工學院<br>大氣科學碩士班<br>103<br>As proposed by previous theoretical and modeling studies of tropical cyclones, when tropical cyclone rainbands are located or advanced over regions beyond the inner-core environment, which can be conceptually considered as the outer rainbands, their associated moist convection would be weakly constrained by the vortex dynamics. The outer rainbands can sometimes develop arc-shaped radar echoes. The observational evidence appears to support that the outer rainbands may exhibit a convective behavior toward the squall-line-like precipitation system. However, this scenario is more speculative than definitive at this stage and has not been verified
because of the lack of detailed kinematic and thermodynamic information within these rainband features.
After Typhoon Matmo (2014) made landfall at Fu-Chien Province on July 23 2014, there were several line echo wave patterns (LEWPs) developing over the southern Taiwan Strait and propagating northeastward. Meanwhile an airplane crashed at Makung Airport, which caused 48 casualties. Therefore, the study represents the characteristics of the LEWPs associated with the outer rainband in Typhoon Matmo (2014) by analyzing observational data collected from both Chinese Airforce Makung dual-pol weather radar and Central Weather Bureau Chiku weather radar. Furthermore, the role that the deep convection play in the rainband and the characteristics of intense vertical velocities, convergence and vertical vorticity are deduced from the analyses of the dual-Doppler synthesized wind.
The results show that the LEWP and associated bookend vortices, which are similar to the bow echo pattern, are well pronounced while typhoon was moving further away from Taiwan. The rear inflow jet also significantly enhanced. The intense upward motion with velocity of 10m s-1 is located at the leading of LEWP, while the intensity of the strong downdraft associated with rear inflow jet with reaches 10m s-1. Additionally, the intensity of the vertical voirticity in bookend vortices which developed at both northern and southern ends of a LEWP are larger than 10-3 s-1 and less than - 10-3 s-1, respectively. The convection is still active in the outer ring of a tropical cyclone and its impact on aviation safety is remarkable for further study.
30
Hong, JingShan, and 洪景山. "Case study of TAMEX IOP13 frontal rainband: the characteristic of the convective behavior." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/90855152826288610849.
Full textAbstract:
博士<br>國立臺灣大學<br>大氣科學系<br>86<br>The paper investigate the convective behavior by using the
dual Doppler radar
observations and the two dimensional nonhydrostatic cloud model. There are
three major part in the paper. The Part I describes the the frontal rainband
by using the observation data and addresses the interested questions
for further studies.
The momentum budget analysis have been studied by using the dual-Doppler
radar wind data and the retrieved perturbation pressure field in part II.
The results show that the pressure gradient force in mid-troposphere, which
results from the interaction of the convective updraft and the vertical wind
shear, plays important roles in the evolution of the long-lifed convective
cell and leads to the tilting of the convection toward the downshear side.
The convection transports the along-line component of momentum down the mean
gradient and the cross-line component upgradient. The downshear tilt of
the convective system is a necessary condition which transports the cross-line
momentum upgradient. Finally, we try to interpret what the interaction of the
convective updraft and the vertical shear is by the momentum
transport thinking.
The horizontal acceleration induced by the vertical momentum flux convergence
tends to generate a high pressure at downstream side and low pressure
at upstream side. The pressure dipole can be considered as the inertia of
the flow field and the associated pressure gradient force tends to offset
the external forcing which is due to the momentum transport. The
inertia depends on the aspect ratio of the external forcing, e.g. , the
pressure gradient force will be larger when the scale along the
forcing is larger than the scale cross the forcing.
In the case, the net force of the momentum flux convergence and the
pressure gradient force will be smaller and tends to keep the initial status
of the flow field. The thinking can be also extended to the
interpretation of the buoyancy induced pressure gradient force.
Part III systematically analyze the charactristics of the downshear tilt
convection by the idealized two dimensional nohydrostatic cloud model
and compare with the observations. By the way, the simulation results also
show that using the CAPE (Convective Available Potential Energy) to present
the convective instability of the atmosphere may casuse
improper interpretation.
The vertical profile of the CAPE is a more realistic idea. By the way, the
eimulataion results also suggest the low level jet will moisterize the
boundary layer and then modify the vertical profile of CAPE, thus favor
the development of the convection.
31
Cheng, Kuang-Hao, and 鄭光浩. "The Reorganization of Rainband after Typhoon Moved Over the Central Mountain Range of Taiwan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/33761385937375023722.
Full text
32
Yang, Hsi-Feng, and 楊錫豐. "A Study of Characterization of Hydrometeor Classification on the Distribution of Rainband in Typhoon." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/91577536134873478023.
Full textAbstract:
碩士<br>國防大學理工學院<br>大氣科學碩士班<br>101<br>Typhoon Meranti(2010) developed from a tropical depression into a tropical storm over the ocean at the west-southwest about 180 km away from Oluanpi at 0000UTC, September 9 2010. It moved to the north and spent almost the entire life cycle in the Taiwan Strait. Clouds in the inner regions of typhoon Meranti(2010) were not obviously damaged by terrain of this period of time. The overall structure of clouds remain very much intact. The evolution of Meranti from 0800 to 2000UTC was observed by Ma-kung C-band dual-polarization radar and Chi-ku S-band Doppler radar. The study seize this rare opportunity of the complete observation data and use the relevant information to retrieve the hydrometeor particle distribution of typhoon Meranti.
In this case, drizzle, rain, supercooled water, graupel, aggregated snowflakes, hail and rain-hail mixture were observed. The Dual-Doppler radar synthesis wind fields were retrieved using Ma-kung C-band dual-polarization radar and Chi-ku S-band Doppler radar radial winds. It explains the phenomenon of the movement of all particles and makes up for the lack of information on the horizontal and vertical spatial structure.
To ensure that the fuzzy logic to identify the particle distribution is credible and the telemetry of radar to cloud microphysical observations of typhoon rainband is availability. During the study period of time, we constantly compare with the study of foreign. Try to piece together the individual three-dimensional structure information to establish the distribution of hydrometeor particles in the overall vertical structure of the typhoon. Finally, we carefully investigated the typhoon rainband to find the association between the hydrometeor particles, dynamics and thermal structure and established the conceptual model of the horizontal and vertical structure of typhoon rainband.
33
Edwalds, Eric. "A numerical study of sulfur and nitrogen scavenging in a mesoscale rainband observed in the GALE experiment." Thesis, 1987. http://hdl.handle.net/1957/29368.
Full text
34
Chen, Po-Hsuan, and 陳伯軒. "The Rainband Feature of Typhoon During the Mei-Yu Season with Southwesterly Flow Effection - Typhoon Talim (2012)." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/qhmbst.
Full textAbstract:
碩士<br>國防大學理工學院<br>大氣科學碩士班<br>103<br>The northerly and southwesterly flows are usually to form a long wind shift line over the southern China Area during mei-yu season. The line can extand over thousands kilometers associated with mesoscale vortex which sometimes intensifies into a tropical cyclone. The meso vortex may trigger strong convective system, inducing heavy rainfall.
Typhoon Talim(2012) origined from a low pressure developing in southern China Area. In the beginning the low pressure connected with the Mei-yu front. It evolved and intenfied into a tropical cyclone after separating from the frontal system.
The environmental analysis showed that the circulation of typhoon Talim was axis-asymmetric. The intense southwesterly flow prevailed on the southeastern side of the circulation. The precipitation over the southern Taiwan Area from 19 to 21 June 2012 was dominated by 2 weather system within 3 period, i.e., southwesterly flow-typhoon rainband- southwesterly flow. The weather radar observation demonstrated that the inner core of typhoon Talim was insignificant. The convective cell embedded with the rainband moved to the dirction different from the moving dirction of typhoon.
The characteristics of the typhoon rainband are revealed by analyzing Makung and Chiku weather radar data while typhoon was passing through Taiwan Strait . The time segitence of Dual-Doppler wind synthesis delineated that the deep convection embedded within the precipitation system A vertically extented over 15 km.
35
Chu-Rong, Yang, and 楊淑蓉. "An analysis of the structure evolution of a mesoscale convective system within a Mei-Yu season frontal rainband." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/06687221993975586454.
Full textAbstract:
碩士<br>國立中央大學<br>大氣物理研究所<br>82<br>IOP\#13於TAMEX期間不同於其他個案且為梅雨期中較為特殊之案例，其與
颮線（squall line) 、雷雨（thunderstorm） 之系統亦不盡相同。在其
長達二十幾小時的生命史中，分別於台灣的中、南部形成了三個集中的大
降雨區。而為研究其緩慢移動及長生命期的特徵，故由分析此雨帶系統之
運動、動力、熱力結構上的演變著手，盼能透過多個連續時間的回波分析
、空氣塊運動軌跡及熱、動力場和渦度場的分析來探討維持此個案長生命
期之機制為何。由6/25 0653LST$\sim$ 6/25 0843LST 約每隔7分鐘一組
資料之回波和合成風場分析結果可知於低層由西風、西南風相遇輻合所形
成之風切線於回波後緣產生，且此輻合作用利於對流上升運動的發展，而
在中層西風，高層西北風的垂直風切影嚮下，致使強回波中心於鋒前東南
側發生。雨帶於台灣地區隨時間往南緩慢移動，幾乎呈滯留狀態，最大回
波深度可發展至15公里高，強回波分佈於分析時間的初期及後期呈較組織
性之形態，中期則分佈較零散。而由氣塊軌跡線的分析結果，可知由強回
波後緣西側入流之氣塊隨時間不斷往上流，提供對流胞足夠的水汽，而由
南側進入之西南氣流則隨時間呈下降趨勢，無法上沖至中、高層。由連續
數個時間之渦度場分析和動力方程式來看，比較各層渦度可發現中上層渦
度較低層強，且於渦度較強處有一相對低壓的存在，因此在垂直氣壓梯度
力向上的情形下，可加速引入來自低層西側的暖濕空氣，維持上沖流之強
度及位置。再者由於渦度的水平分佈變化不大，再加上垂直速度的佈亦變
化不大，故使垂直速度之水平梯度維持，且在變化不大的環境風切作用下
，便可穩定維持水平渦度。如此週而復始，再加上中低層暖空氣與降水系
統間的輻合場，與高層環境所存在之分流場，故在此三要素作用下，垂直
速度得以維持一定強度，亦應而致使 IOP\#13得以維持其長生期。