首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
This study investigates microphysical properties from wind profiler Doppler spectra observed within a precipitation system that produced high rainfall rates up to 40 mm hr?1 near the southern coast of the Korean Peninsula on 25～26 June 2010. A 1290-MHz wind profiler located in the National Center for Intensive Observation of Severe Weather at Boseong, Korea, observed a widespread stratiform region and short-lived convective cells from 1850 UTC 25 to 0200 UTC 26 June 2010. By using a spectral model applied to observed profiler spectra, rainfall parameters and raindrop size distributions were retrieved below a melting layer during this period. Three representative periods during precipitation were selected based on intensities of bright band and characteristics in vertical profiles of radar reflectivity and Doppler velocity. During a brief convective period (～30 min), radar reflectivity tended to be proportional to vertical air motion (positive upward), suggesting that updrafts up to ～3 m s?1 over a large vertical extent through the melting layer probably contributed to increasing rainfall rates at the surface. In reflectivityrainfall rate distributions, large drop spectra (high reflectivity) were analyzed within downdrafts and small drop spectra (low reflectivity) within updrafts, similar to the large and small drop spectra but found in stratiform and convective regions, respectively, in previous studies. This indicates that the degree of spread between reflectivity and rainfall rate may be strongly dependent on positive and negative magnitudes of vertical air motion. For three categories of vertical air motion (i.e., updrafts, neutral, and downdrafts), physical relations between the retrieved rainfall parameters were examined.  相似文献   

2.
Finescale spiral rainbands associated with Typhoon Rananim(2004)with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model(MM5).The finescale rainbands have two types:one intersecting the eyewall and causing damaging wind streaks,and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime.The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity.The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high altitude.The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands,consistent with previous findings using simple symmetric models.In particular,the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands.The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow.The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands,and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.  相似文献   

3.
Microphysical characteristics of the raindrop size distribution(RSD)in Typhoon Morakot(2009) have been studied through the PARSIVEL disdrometer measurements at one site in Fujian province,China during the passage of the storm from 7 to 10 August 2009.The time evolution of the RSD reveals different segments of the storm.Significant difference was observed in the microphysical characteristics between the outer rainband and the eyewall;the eyewall precipitation had a broader size distribution(a smaller slope) than the outer rainband and eye region.The outer rainband and the eye region produced stratiform rains while the eyewall precipitation was convective or mixed stratiform-convective.The RSD was typically characterized by a single peak distribution and well represented by the gamma distribution.The relations between the shape(μ)and slope(Λ)of the gamma distribution and between the reflectivity(Z)and rainfall rate(R)have been investigated.Based on the NW-Dm relationships,we suggest that the stratiform rain for the outer rainband and the eye region was formed by the melting of graupel or rimed ice particles,which likely originated from the eyewall clouds.  相似文献   

4.
Super Typhoon Haiyan (1330), which occurred in 2013, is the most powerful typhoon during landfall in the meteorological record. In this study, the temporal and spatial distributions of lightning activity of Haiyan were analyzed by using the lightning data from the World Wide Lightning Location Network, typhoon intensity and position data from the China Meteorological Administration, and horizontal wind data from the ECMWF. Three distinct regions were identified in the spatial distribution of daily average lightning density, with the maxima in the inner core and the minima in the inner rainband. The lightning density in the intensifying stage of Haiyan was greater than that in its weakening stage. During the time when the typhoon intensity measured with maximum sustained wind speed was between 32.7 and 41.4 ms?1, the storm had the largest lightning density in the inner core, compared with other intensity stages. In contrast to earlier typhoon studies, the eyewall lightning burst out three times. The first two eyewall lightning outbreaks occurred during the period of rapid intensification and before the maximum intensity of the storm, suggesting that the eyewall lightning activity could be used to identify the change in tropical cyclone intensity. The flashes frequently occurred in the inner core, and in the outer rainbands with the black body temperature below 220 K. Combined with the ECMWF wind data, the influences of vertical wind shear (VWS) on the azimuthal distribution of flashes were also analyzed, showing that strong VWS produced downshear left asymmetry of lightning activity in the inner core and downshear right asymmetry in the rainbands.  相似文献   

5.
In this study, fine structures of spiral rainbands in super Typhoon Chanchu (2006) are examined using an Advanced Research Weather Research and Forecast (WRF-ARW) model simulation with the finest grid size of 2 km. Results show that the simulation reproduces well Typhoon Chanchu’s track, intensity and basic structures. According to their locations and features, spiral rainbands are classified into principal, secondary, inner and distant rainbands, and their dynamic and thermodynamic features are investigated. The principal rainbands remain quasi-stationary with respect to Chanchu’s center and exhibit a wavenumber-1 feature with their outer edges separated by dry air. The secondary rainbands that occur on the radially inward side of the principal rainbands move around Chanchu''s center. The inner rainbands are closest to the center. They propagate both radially outward and azimuthally with time. The distant rainbands are located outside the inner-core region, and have stronger and continuous updrafts compared to the other rainbands. Distant rainbands are inward-sloping with height along the radial direction and have a cold pool in the low layers, whereas the principal and secondary rainbands lean radially outward with height. The inner rainbands do not show tilting with height along the radial direction. However, there are few vertical tilting cells along the azimuthal orientation among the four types of rainbands. The simulated radar reflectivity cores in all rainbands are collocated with the maxima of updrafts and equivalent potential temperatures in the low layer, indicating the important roles of energy supply in the boundary layer in determining the development of the rainband convection.  相似文献   

6.
Multisatellite data is used to analyze the characteristics of three eyewall replacement cycles (ERCs) during the lifetime of Typhoon Muifa (1109). Spiral rainbands evolutions, concentric eyewall (CE) structure modes, CE durations, and intensity changes are discussed in detail. In addition, an ERC evolution model of Typhoon Muifa is given. There are four main findings. (1) The outer spiral rainband joins end to end to form the outer eyewall after it disconnects from the original (inner) eyewall. The inner eyewall weakens as the outer eyewall becomes axisymmetric and is intensified. The contraction of the outer eyewall causes the inner eyewall to dissipate rapidly. Finally, the ERC ends with an annular eyewall or spiral rainbands. (2) Although the CE duration times of Typhoon Muifa’s three ERCs covered a large range, the CE structures were all maintained for approximately 5 h from the formation of the axisymmetric outer eyewall to the end of the cycle. (3) There is no obvious precipitation reflectivity in the eye or moat region for the subsidence flow. The convection within the two eyewalls is organized as a radially outward slope with increasing height. (4) Typhoon intensity estimation results based on ADT may not explain the intensity variations associated with ERC correctly, while the typhoon’s warm core data retrieved from AMSU-A works well.  相似文献   

7.
By using WRF mesoscale model, this paper carries out a numerical simulation and diagnostic analysis of the structural characteristics of the asymmetric spiral rain bands around the landing of Typhoon Haitang during the period of July 19 to 20, 2005. The result indicated that the two rainbands associated with the precipitation centre was mainly located northeast of the typhoon centre. The movement and intensity of the southern rainband corresponded well with the 850-hPa positive vorticity band from 0200 to 1800 UTC July 19, 2005. Under the effect of cyclonic circulation, the positive vorticity band at 850 hPa connected with a southern rain band, leading to the intensification of rainfall in the southern centre of the precipitation. The southward rainband gradually moved toward and then merges with the northward one, strengthening the rainfall in the northern centre of the precipitation. Besides, the relationship between the heavy rainfall and the divergence field of vertical shear wind in the high altitude is analyzed. Finally, the relationship is revealed between the development of the vertical component of convective vorticity vector and the rainfall near the two centres of precipitation in the low altitude.  相似文献   

8.
超强台风＂韦帕＂（Wipha）是2007年登陆中国大陆最强的台风,在浙江省造成了特大暴雨。利用宁波和舟山双多普勒天气雷达同步观测资料,对＂韦帕＂的两条螺旋雨带进行了双雷达三维风场反演;并综合利用组网雷达拼图数据等资料,对螺旋雨带的三维精细结构进行了分析。研究表明：（1）两条螺旋雨带的三维结构有很多相似之处。螺旋雨带内部低层有多个强回波区,水平速度大值区主要分布在强回波带上;强回波带的低层有较强的上升气流,最强上升气流超过4 m/s。在螺旋雨带中存在多个辐合辐散对、上升下沉气流对,这对于螺旋雨带的维持和进一步发展具有重要作用。在沿着台风中心的垂直剖面内,螺旋雨带内部的强回波区向雨带外侧倾斜。雨带外侧2 km高度以下的低层有较强的内流,最大值为5 m/s;雨带内侧有较强的外流,2 km高度以上均受外流控制;内流和外流在雨带中部低层汇合抬升。切向速度的强中心出现在3 km高度,速度值随高度增加而逐渐减小。（2）两个时段的螺旋雨带也存在差异。前一个时段的螺旋雨带对流发展更旺盛,45 dBZ的回波高度为4.8 km,而后一个时段的螺旋雨带45 dBZ的回波高度仅3.2 km。垂直剖面内,前一个时刻螺旋雨带低层辐合更强,最强辐合值超过-15×10^-4s^-1,正是由于低层的强辐合和充足的水汽供应,才使得雨带内部中低层的回波发展旺盛。  相似文献   

9.
The mechanism responsible for high rainfall over the Indian west coast region has been investigated by studying dynamical, thermodynamical and microphysical processes over the region for the monsoon season of 2009. The European Centre for Medium-Range Weather Forecasts wind and NCEP flux data have been used to study the large scale dynamical parameters. The moist adiabatic and multi-level inversion stratifications are found to exist during the high and low rainfall spells, respectively. In the moist adiabatic stratification regime, shallow and deep convective clouds are found coexisting. The Cloud Aerosol Interaction and Precipitation Enhancement EXperiment aircraft data showed cloud updraft spectrum ranging from 1 to 10 m s?1 having modal speed 1–2.5 m s?1. The low updrafts rates provide sufficient time required for warm rain processes to produce rainfall from shallow clouds. The low cloud liquid water is observed above the freezing level indicating efficient warm rain process. The updrafts at the high spectrum end go above freezing level to generate ice particles produced due to mixed-phase rainfall process from deep convective clouds. With aging, deep convection gets transformed into stratiform type, which has been inferred through the vertical distribution of the large scale omega and heating fields. The stratiform heating, high latent heat flux, strong wind shear in the lower and middle tropospheric levels and low level convergence support the sustenance of convection for longer time to produce high rainfall spell. The advection of warm dry air in the middle tropospheric regions inhibits the convection and produce low rainfall spell. The mechanisms producing these spells have been summarized with the block diagram.  相似文献   

10.
The impact of cloud microphysical processes on the simulated intensity and track of Typhoon Rananim is discussed and analyzed in the second part of this study. The results indicate that when the cooling effect due to evaporation of rain water is excluded, the simulated 36-h maximum surface wind speed of Typhoon Rananim is about 7 m s−1 greater than that from all other experiments; however, the typhoon landfall location has the biggest bias of about 150 km against the control experiment. The simulated strong outer rainbands and the vertical shear of the environmental flow are unfavorable for the deepening and maintenance of the typhoon and result in its intensity loss near the landfall. It is the cloud microphysical processes that strengthen and create the outer spiral rainbands, which then increase the local convergence away from the typhoon center and prevent more moisture and energy transport to the inner core of the typhoon. The developed outer rainbands are supposed to bring dry and cold air mass from the middle troposphere to the planetary boundary layer (PBL). The other branch of the cold airflow comes from the evaporation of rain water itself in the PBL while the droplets are falling. Thus, the cut-off of the warm and moist air to the inner core and the invasion of cold and dry air to the eyewall region are expected to bring about the intensity reduction of the modeled typhoon. Therefore, the deepening and maintenance of Typhoon Rananim during its landing are better simulated through the reduction of these two kinds of model errors.  相似文献   

11.
Super Typhoon Haiyan(1330), which occurred in 2013, is the most powerful typhoon during landfall in the meteorological record. In this study, the temporal and spatial distributions of lightning activity of Haiyan were analyzed by using the lightning data from the World Wide Lightning Location Network,typhoon intensity and position data from the China Meteorological Administration, and horizontal wind data from the ECMWF. Three distinct regions were identified in the spatial distribution of daily average lightning density, with the maxima in the inner core and the minima in the inner rainband. The lightning density in the intensifying stage of Haiyan was greater than that in its weakening stage. During the time when the typhoon intensity measured with maximum sustained wind speed was between 32.7 and 41.4 m s-1, the storm had the largest lightning density in the inner core, compared with other intensity stages.In contrast to earlier typhoon studies, the eyewall lightning burst out three times. The first two eyewall lightning outbreaks occurred during the period of rapid intensification and before the maximum intensity of the storm, suggesting that the eyewall lightning activity could be used to identify the change in tropical cyclone intensity. The flashes frequently occurred in the inner core, and in the outer rainbands with the black body temperature below 220 K. Combined with the ECMWF wind data, the influences of vertical wind shear(VWS) on the azimuthal distribution of flashes were also analyzed, showing that strong VWS produced downshear left asymmetry of lightning activity in the inner core and downshear right asymmetry in the rainbands.  相似文献   

12.
高拴柱 《气象》2020,46(6):792-800
利用中央气象台中尺度地面降水观测资料、气象雷达观测资料和NCEP FNL资料,以及中国气象局上海台风研究所台风最佳路径资料,研究了2018年台风温比亚深入内陆后造成华东地区强降水的雨带结构和演变特征及天气尺度背景环境。结果表明:“温比亚”登陆后的雨带在皖豫鲁交界和山东中南部两度表现为多条短螺旋雨带合并发展为单一长雨带的特征;雨带的维持和形态演变主要是“温比亚”台风环流和强度维持及其与副热带高压的停滞西伸加强的相互作用决定的;由于低层垂直风切变的加强,两条长雨带分别在其起端的安徽北部和山东南部两度表现出显著的对流特征,并都伴有龙卷的发生。  相似文献   

13.
在分析云微物理参数化对云结构和降水特征的影响的基础上,研究云微物理参数化过程对台风"云娜"强度与路径的影响.结果表明:云微物理过程对台风强度和路径有一定影响,其中不考虑雨水蒸发冷却效应后,比其他试验最终地面最大风速强7 m/s以上,但此时登陆地点误差最大,与对照试验偏离150 km左右.我们还从螺旋雨带结构变化及环境风切变影响角度分析台风临近登陆时强度模拟减弱的原因,发现过强的外围螺旋雨带以及环境风场垂直切变对于台风的加深、维持是不利的,他们可能会造成"云娜"临近登陆时强度的下降.不难看出,云微物理过程可以加强甚至产生外螺旋雨带,当外围雨带发展加强之后,可以引起局地辐合强度增强,从而限制了大量水汽和能量向台风内核输送,从而会导致台风强度下降.此外,外围螺旋雨带的发展,还可以从对流层中层带来干冷空气入侵行星边界层;而当入流边界层中雨水下落时,其自身的蒸发也会使周围气块温度下降;这些干冷气团在入流气流的输送下进入台风内核,从而对云墙产生了"冷侵蚀",最终引起台风强度下降.因此,减小上述两方面的模拟误差,应能改进台风"云娜"登陆过程中强度的模拟效果.  相似文献   

14.
C-FMCW雷达对江淮降水云零度层亮带探测研究   总被引：2，自引：2，他引：0       下载免费PDF全文
不同于体扫雷达探测降水系统,垂直指向雷达可探测降水云中粒子垂直演变的微物理过程。C波段调频连续波垂直指向雷达 (C-FMCW) 采用收发分置天线,数据垂直分辨率达15~30 m,时间分辨率达2~3 s,利用其2013年6—8月在安徽定远探测数据对降水云垂直结构特征及亮带中融化微物理过程进行研究。6次降水过程共计46 h中的39.1%数据具有清晰的亮带结构特征,期间降水占地面总降水量的15%;江淮雨季层状云、对流云和混合性降水系统中均出现零度层亮带,层状云中亮带长时间维持,对流降水系统移出后减弱阶段的亮带结构稳定,混合降水系统中的对流扰动加强冲破了亮带结构。以融化层中最大回波强度Zp所在高度进行融化层的粒子碰并增长和破碎减弱分层分析,上半层融化过程主要表现为碰并增长,下半层则是粒子破碎减弱。剔除了介电常数、下降速度引起的粒子浓度改变影响后,层状云和对流降水后期的回波强度加强表明融化增长程度接近,后者略强,混合降水云的融化增长最强。  相似文献   

15.
Previous numerical simulations have focused mainly on the mesoscale structure of the principal rainband in tropical cyclones with a relatively coarse model resolution. In this study, the principal rainband was simulated in a semi-idealized experiment at a horizontal grid spacing of 1/9 km and its convective-scale structure was examined by comparing the convective elements of the simulated principal rainband with previous observational studies. It is found that the convective scale structure of the simulated principal rainband is well comparable to the observation.　　The azimuthal variations of the convective scale structure were examined by dividing the simulated principal rainband into the upwind, middle and downwind portions. Some new features are found in the simulated principal rainband. First, the overturning updraft contains small-scale rolls aligned along the inward side of the outward-leaning reflectivity tower in the middle portion. Second, the inner-edge downdraft is combined with a branch of inflow from the upper levels in middle and downwind portions, carrying upper-level dry air to the region between the overturning updrafts and eyewall, and the intrusion of the upper-level dry air further limits the altitude of the overturning updrafts in the middle and downwind portions of the principal rainband. Third, from the middle to downwind portions, the strength of the secondary horizontal wind maximum is gradually replaced by a low-level maximum of the tangential wind collocated with the low-level downdraft.  相似文献   

16.
By using the Advanced Regional Eta-coordinate Model (AREM),the basic structure and cloud features of Typhoon Rananim are simulated and verified against observations.Five sets of experiments are designed to investigate the effects of the cloud microphysical processes on the model cloud structure and precipitation features.The importance of the ice-phase microphysics,the cooling effect related to microphysical characteristics change,and the influence of terminal velocity of graupel are examined.The results indicate that the cloud microphysical processes impact more on the cloud development and precipitation features of the typhoon than on its intensity and track.Big differences in the distribution pattern and content of hydrometeors,and types and amount of rainfall occur in the five experiments,resulting in different heating and cooling effects.The largest difference of 24-h rain rate reaches 52.5 mm h-1.The results are summarized as follows:1) when the cooling effect due to the evaporation of rain water is excluded,updrafts in the typhoon's inner core are the strongest with the maximum vertical velocity of-19 Pa s-1 and rain water and graupel grow most dominantly with their mixing ratios increased by 1.8 and 2.5 g kg-1,respectively,compared with the control experiment; 2) the melting of snow and graupel affects the growth of rain water mainly in the spiral rainbands,but much less significantly in the eyewall area; 3) the warm cloud microphysical process produces the smallest rainfall area and the largest percentage of convective precipitation (63.19％),while the largest rainfall area and the smallest percentage of convective precipitation (48.85％) are generated when the terminal velocity of graupel is weakened by half.  相似文献   

17.
The impact of cloud microphysical processes on the simulated intensity and track of Typhoon Rananim is discussed and analyzed in the second part of this study.The results indicate that when the cooling effect due to evaporation of rain water is excluded,the simulated 36-h maximum surface wind speed of Typhoon Rananim is about 7 m s-1 greater than that from all other experiments; however,the typhoon landfall location has the biggest bias of about 150 km against the control experiment.The simulated strong outer rainbands and the vertical shear of the environmental flow are unfavorable for the deepening and maintenance of the typhoon and result in its intensity loss near the landfall.It is the cloud microphysical processes that strengthen and create the outer spiral rainbands,which then increase the local convergence away from the typhoon center and prevent more moisture and energy transport to the inner core of the typhoon.The developed outer rainbands are supposed to bring dry and cold air mass from the middle troposphere to the planetary boundary layer (PBL).The other branch of the cold airflow comes from the evaporation of rain water itself in the PBL while the droplets are falling.Thus,the cut-off of the warm and moist air to the inner core and the invasion of cold and dry air to the eyewall region are expected to bring about the intensity reduction of the modeled typhoon.Therefore,the deepening and maintenance of Typhoon Rananim during its landing are better simulated through the reduction of these two kinds of model errors.  相似文献   

18.
Idealized numerical simulations are conducted in this study to comparatively investigate the characteristics of the stratiform sector in the outer rainbands of tropical cyclones(TCs)in lower-and upper-layer vertical wind shear(VWS)with moderate magnitude.Consistent with the results in previous studies,the outer rainband stratiform sector of the TCs simulated in both experiments is generally located downshear left.Upper-layer VWS tends to produce stronger asymmetric outflow at upper levels in the downshear-left quadrant than lower-layer shear.This stronger asymmetric outflow transports more water vapor radially outward from the inner core to the outer core at upper levels in the downshear-left quadrant in the upper-layer shear experiment.More depositional growth of both graupel and cloud ice thus occurs downshear left in upper layers in the outer core,yielding more diabatic heating and stronger upward motions,particularly in the stratiformdominated part of the stratiform sector in the upper-layer shear experiment.Resultingly,a better-organized stratiform sector in the outer rainbands is found in the upper-layer VWS experiment than in the lower-layer VWS experiment.The diabatic heating associated with the stratiform sector produces strong midlevel outflow on the radially inward side of,and weak midlevel inflow on the radially outward side of,the heating core,with lower-level inflow beneath the midlevel outflow and upper-level inflow above.The upper-layer VWS tends to produce a deeper asymmetric inflow layer in the outer rainband stratiform sector,with more significant lower-level inflow and tangential jets in the upper-layer VWS experiment.  相似文献   

19.
In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and upshear right(UR)]during the final landfall of Typhoon Ewiniar(2018) is analyzed using two-dimensional video disdrometer and S-band polarimetric radar data collected in Guangdong, China. Due to the different types of underlying surfaces, the periods before landfall(mainly dominated ...  相似文献   

20.
The effects of environmental vertical wind shear(VWS)on the intensity and rainfall asymmetries in Tropical Storm(TS)Bilis(2006)have been analyzed based on TRMM/TMI-estimated surface rainfall data,QuikSCAT wind fields,850-and 200-hPa winds of the NCEP-NCAR reanalysis,precipitation data at 5-min intervals from automatic weather stations over mainland China,and the best track data of TS Bilis(2006). The results show that the simultaneous and 6-hour-lagged correlation coeffcients between VWS and storm intensity(the minimum central sea level pressure)are 0.59145 and 0.57438(P0.01),respectively.The averaged VWS was found to be about 11 m s-1 and thus suppressed the intensification of Bilis(2006). Distribution of precipitation in Bilis(2006)was highly asymmetric.The azimuthally-averaged rainfall rate in the partial eyewall,however,was smaller than that in a major outer rainband.As the storm intensified,the major rainband showed an unusual outward propagation.The VWS had a great impact on the asymmetric distribution of precipitation.Consistent with previous modeling studies,heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall,showing a strong wavenumber-one asymmetry,which was amplified as the VWS increased.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号