利用TRMM资料分析2002年登陆广东的热带气旋降水分布特征

用2002年3个热带气旋登陆广东的过程中自动站的降水资料, 对TRMM准全球、准实时的3 h降水估测资料进行了检验, 表明该资料与地面3 h降水有很好的相关性, 可以反映出热带气旋3 h降水变化的特征。利用该资料分析了这3个热带气旋登陆过程中不同半径、不同方向降水的时空变化特征, 并分析了不同热带气旋之间降水差异的大尺度环流背景。研究发现, 3个热带气旋登陆过程中心附近降水沿半径方向存在收缩和扩展的变化, 除了低层水汽输送的变化和地形对降水造成影响之外, “北冕”和“黄蜂”都发现热带气旋外围降水加强会导致其中心附近降水减弱, 这与以往的观测及研究成果类似。     

AN OBSERVATIONAL STUDY ON DISTRIBUTION OF PRECIPITATION ASSOCIATED WITH LANDFALLING TROPICAL CYCLONES AFFECTING CHINA

In order to provide an operational reference for tropical cyclone precipitation forecast,this study investigates the spatial distributions of precipitation associated with landfalling tropical cyclones(TCs) affecting China using Geostationary Meteorological Satellite 5(GMS5)-TBB dataset.All named TCs formed over the western North Pacific that made direct landfall over China during the period 2001-2009 are included in this study.Based on the GMS5-TBB data,this paper reveals that in general there are four types of distribution of precipitation related to landfalling TCs affecting China.(a) the South-West Type in which there is a precipitation maximum to the southwestern quadrant of TC;(b) the Symmetrical South Type in which the rainfall is more pronounced to the south side of TC in the inner core while there is a symmetrical rainfall distribution in the outer band region;(c) the South Type,in which the rainfall maxima is more pronounced to the south of TC;and(d) the North Type,in which the rainfall maxima is more pronounced to the north of TC.Analyses of the relationship between precipitation distributions and intensity of landfalling TCs show that for intensifying TCs,both the maximum and the coverage area of the precipitation in TCs increase with the increase of TC intensity over northern Jiangsu province and southern Taiwan Strait,while decreasing over Beibu Gulf and the sea area of Changjiang River estuary.For all TCs,the center of the torrential rain in TC shifts toward the TC center as the intensity of TC increases.This finding is consistent with many previous studies.The possible influences of storm motion and vertical wind shear on the observed precipitation asymmetries are also examined.Results show that the environmental vertical wind shear is an important factor contributing to the large downshear rainfall asymmetry,especially when a TC makes landfall on the south and east China coasts.These results are also consistent with previous observational and numerical studies.     

A COMPOSITE STUDY OF RAINFALL ASYMMETRY OF TROPICAL CYCLONES AFTER MAKING LANDFALL IN GUANGDONG PROVINCE

Based on observed rainfall data, this study makes a composite analysis of rainfall asymmetry in tropical cyclones(TCs) after making landfall in Guangdong province(GD) during 1998—2015. There are 3.0 TCs per year on average making landfall in GD and west of GD(WGD) has the most landfall TCs. Most of TCs make landfall in June,July, August, and September at the intensities of TY, STS, and TS. On average, there is more rainfall in the southwest quadrant of TC in CGD(center of GD), WGD, and GD as a whole, and the maximum rainfall is located in the southwest near the TC center. The mean TC rainfall in the east of GD(EGD) leans to the eastern side of TC. The TC rainfall distributions in June, July, August, and September all lean to the southwest quadrant and the maximum rainfall is located in the southwest near the TC center. The same features are found in the mean rainfall of TD, TS, STS, TY,and STY. The maximum rainfall is mainly in the downshear of vertical wind shear. Vertical wind shear is probably the dominate factor that determines asymmetric rainfall distribution of TCs in GD. Storm motion has little connection with TC rainfall asymmetry in GD.     

基于MTCSWA风场资料对西北太平洋热带气旋风场结构的气候统计特征研究

基于多平台热带气旋表面风场资料（MTCSWA）,研究了2007～2016年6～11月西北太平洋上不同尺度热带气旋（TC）的气候统计特征,TC各级风圈半径在不同象限的变化特征、风场结构的对称度及二者与强度变化之间的相关性。利用7级风圈半径与TC近中心最大持续风速（MSW）来定义TC的尺度和强度。结果表明,西北太平洋上TC的平均尺度为221.9 km,其中小TC平均尺度为96.4 km,大TC平均尺度为346.4 km。大TC活动位置的空间分布较小TC更为集中,整体活动范围较小TC偏北。TC尺度的峰值出现在8月和10月。在TC的风场结构中,7级、10级、12级风圈的平均半径分别为221.9、121.0、77.4 km。TC风圈的对称度的统计结果表明7级风圈的对称度最低,12级风圈的对称度最高。相关分析表明,在TC的生命史中,各级风圈半径与其强度存在一定的正相关关系,其中12级风圈半径与强度的相关性最低;对于同一风圈而言,在TC的不同发展阶段中,不同象限的风圈半径与强度的相关性不同。在TC的风场结构中,风圈的对称度与TC强度的相关性随着风圈强度的增强而减弱,只有7级风圈的对称度在TC的整个生命周期中表现出与TC强度之间的弱的正相关关系。     

OBSERVATION RESEARCH FOR THE MEASURING RAINFALL CAPACITY OF TRMM/TMI-85.5G BASED ON PRECIPITATION DATA DURING THE HEAVY RAIN EXPERIMENT IN SOUTHERN CHINA

The capacity of Tropical Rainfall Measuring Mission (TRMM) Satellite for measuring rainfall was examined by using TMI-85.5 GHz microwave image data and precipitation data during a heavy rainfall experiment in southern China. From comparisons with the distribution of rain amount in an hour with BB T of 85.5 GHz microwave, it is clear that the center of heavy rain corresponds with an area of low BB T value. The location and shape of BB T distribution is similar to that of precipitation, and the larger the rainfall rates, the lower the BB T . A statistic analysis shows that the correlation coefficients between BB T and rain rates is negative and significant. Especially, when the rain rate is over 7 mm/h, the correlation degree between BB T and rain rates is more significant. The results shows that TRMM/TMI-85.5 G has great ability to measure convective heavy rain.     

Effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries over the North Indian Ocean

Tropical cyclone (TC) rainfall asymmetry is often influenced by vertical wind shear and storm motion. This study examined the effects of environmental vertical wind shear (200-850 hPa) and storm motion on TC rainfall asymmetry over the North Indian Ocean (NIO): the Bay of Bengal (BoB) and the Arabian Sea (AS). Four TC groups were used in this study: Cyclonic Storm (CS), Severe Cyclonic Storm (SCS), Very Severe Cyclonic Storm (VSCS) and Extreme Severe Cyclonic Storm (ESCS). The Fourier coefficients for wave number-1 was used to analyze the structure of TC rainfall asymmetry. Results show that the maximum TC rainfall asymmetry was predominantly in the downshear left quadrant in the BoB, while it placed to downshear right quadrant in the AS, likely due to the different primary circulation strength of the TC vortex. For the most intense cyclone (ESCS), the maximum TC rainfall asymmetry was in the upshear left quadrant in the BoB, whereas it was downshear right quadrant in the AS. It is evident for both basins that the magnitude of TC rainfall asymmetry declined (increased) with TC intensity (shear strength). This study also examined the collective effects of vertical wind shear and storm motion on TC rainfall asymmetry. Here, the analysis in case of the strong shear environment (>7 m s^-1) omitted for the AS because the maximum value for this basin was about 7 m s^-1. The result showed that the downshear left quadrant was dominant in the BoB for the maximum TC rainfall asymmetry. In a weak shear environment (<5 m s^-1), on the other hand, downshear right quadrant is evident for the maximum TC rainfall asymmetry in the BoB, while it placed dominantly downshear left quadrant in the AS. In the case of motion-relative wavenumber-1, the maximum TC rainfall asymmetry was dominantly downshear for both basins.     

TRMM卫星与机载雷达在降雨反演中的数据对比个例研究

热带降水测量卫星（TRMM）上搭载的测雨雷达是第一部能够提供三维降水信息的星载雷达,机载雷达也能够对降雨进行实时观测。由于机载和星载雷达观测有很多共同点,所以选择机载、星载雷达数据进行对比。1998年8月26日NOAA/P3飞机对Bonnie飓风进行了一次观测飞行,与此同时TRMM卫星也同步扫过该区域,因此利用对Bonnie飓风的机、星观测数据对应点数值对比、差值对比、平均值对比等,对Bonnie飓风做了进一步分析。对比结果一致,印证了TRMM数据的可靠性,同时进一步验证了双束立体雷达算法的联合算法的可靠性。     

Satellite estimates and subpixel variability of rainfall in a semi-arid grassland

卫星估雨精度的不确定性受到当地降雨类型和像元内降雨非均匀性影响,而结合这两个关键因素开展半干旱草原卫星估雨的研究有限.2009年夏,我们在中国锡林郭勒半干旱草原用多部微雨雷达和雨量计构建了9 km卫星像元降雨观测网,观测了像元内降雨非均匀性(空间变异系数CV),并评估了卫星估雨精度.结果表明:(1)CV值受像元内平均降雨量,降雨类型,降雨云面积及移向等影响,如高Cv值的降雨过程大多为平均降雨量小,对流性降雨过程,降雨云边缘像元CV值较高;(2)TRMM 3B42V7卫星估雨产品适用性较好,CMORPH和PERSIANN次之,但TRMM 3B42V7易在半干旱草原湖泊处高估降雨.     

利用TMI反演的水汽凝结物对热带气旋潜热结构分布的探索研究

本文利用热带测雨卫星TRMM（Tropical Rainfall Measuring Mission）微波成像仪TMI（TRMM Microwave Imager）2A12 水汽凝结物（Hydrometeor）反演资料,对西北太平洋地区从1998～2009 年的236 个热带气旋个例的1776 个“快照”（snapshot）的水汽凝结物的结构特征进行了分析,并探讨了水汽凝结物的时空变化与热带气旋强度演变联系。研究结果表明:（1）TMI 2A12 水汽凝结物资料显示出了热带气旋内部的细致结构及变化特征,水汽凝结物的峰值集中于数十公里到一百多公里的热带气旋眼壁及云墙区;在热带气旋发展过程中,随着热带气旋强度的增强,水汽凝结物增多且往其中心靠拢,从发展阶段到成熟阶段,水汽凝结物的大值中心基本上集中在距离热带气旋中心约50 km 区域,而且强度越强的热带气旋,水汽凝结物的大值中心与热带气旋中心的距离越近;在热带气旋消亡的过程中,水汽凝结物不断减弱且往外围扩散,逐渐扩展到远离中心的区域;（2）热带气旋强度与水汽凝结物的分布关系密切,热带气旋强度变化与热带气旋中心附近200 km 范围内的水汽凝结物含量存在显著的正相关,而200 km 以外的外围水汽凝结物含量存在负相关;（3）热带气旋强度变化与水汽凝结物的变化存在时间差,水汽凝结物的变化超前于热带气旋强度的变化,在热带气旋迅速发展之前数小时,热带气旋中心0～50 km 环状区域的水汽凝结物含量就已经提前增加了,在热带气旋减弱前数小时到十数小时,即使热带气旋还处于它强度的鼎盛时期,其中心0～50 km 环状区域的水汽凝结物含量就已经提前显著减少了,这种水汽凝结物的变化超前于热带气旋强度的变化的现象,可能是热带气旋强度预报的潜在线索。     

登陆广东北上路径热带气旋强降水的分布特征

利用1981-2018年中国气象局上海台风研究所热带气旋最佳路径资料和国家基本气象站逐日降水资料,对登陆广东北上路径热带气旋活动及强降水特征进行统计分析.结果表明北上热带气旋从登陆时到登陆后48 h是陆地强降水产生的集中时段,登陆时24 h是陆地大暴雨最集中的时段.强降水从沿海向内陆逐渐减少,一般登陆后热带气旋持续时间...     

ANALYSIS OF CAUSATION OF ASYMMETRIC PRECIPITATION ASSOCIATED WITH SEVERE TYPHOON DAMREY

Severe typhoon Damrey moved across Hainan Island from 00:00 UTC 25 September to 00:00 UTC 27 September in 2005 and gave rise to a significant rain process during its 48-h passage. The precipitation intensity on the southern part of the island is stronger than that on the northern, showing obvious asymmetric distribution. Using Tropical Rainfall Measuring Mission (TRMM) data, the associated mesoscale characteristics of the precipitation were analyzed and the formation of asymmetric rainfall distribution was investigated in the context of a subsynoptic scale disturbance, vertical wind shear and orographic factors. The results are shown as follows. (1) The subsynoptic scale system provided favorable dynamic conditions to the genesis of mesoscale rain clusters and rainbands. (2) The southern Hainan Island was located to the left of the leeward direction of downshear all the time, being favorable to the development of convection and leading to the asymmetric rainfall distribution. (3) Mountain terrain in the southern Hainan Island stimulated the genesis, combination and development of convective cells, promoting the formation of mesoscale precipitation systems and ultimately resulting in rainfall increase in the southern island.     

Diurnal Variation of Tropical Cyclone Rainfall in the Western North Pacific in 2008-2010

Diurnal variation of tropical cyclone (TC) rainfall in the western North Pacific (WNP) is investigated using the high-resolution Climate Prediction Center's morphing technique (CMORPH) products obtained from the National Oceanic and Atmospheric Administration (NOAA). From January 2008 to October 2010, 72 TCs and 389 TC rainfall days were reported by the Joint Typhoon Warning Center's (JTWC) best-track record. The TC rain rate was partitioned using the Objective Synoptic Analysis Technique (OSAT) and interpolated into Local Standard Time (LST). Harmonic analysis was applied to analyze the diurnal variation of the precipitation. Obvious diurnal cycles were seen in approximately 70% of the TC rainfall days. The harmonic amplitude and phase of the mean TC rainfall rate vary with TC intensity, life stage, season, and spatial distribution. On the basis of intensity, tropical depressions (TDs) exhibit the highest precipitation variation amplitude (PVA), at approximately 30%, while super typhoons (STs) contain the lowest PVA, at less than 22%. On the basis of lifetime stage, the PVA in the decaying stage (more than 37%) is stronger than that in the developing (less than 20%) and sustaining (28%) stages. On the basis of location, the PVA of more than 35% (less than 18%) is the highest (lowest) over the high-latitude oceanic areas (the eastern ocean of the Philippine Islands). In addition, a sub-diurnal cycle of TC rainfall occurs over the high-latitude oceans. On the basis of season, the diurnal variation is more pronounced during summer and winter, at approximately 30% and 32%, respectively, and is weaker in spring and autumn, at approximately 22% and 24%, respectively.     

Tropical Precipitation Estimated by GPCP and TRMM PR Observations

In this study, tropical monthly mean precipitation estimated by the latest Global Precipitation Climatology Project （GPCP） version 2 dataset and Tropical Rainfall Measurement Mission Precipitation Radar （TRMM PR） are compared in temporal and spatial scales in order to comprehend tropical rainfall climatologically. Reasons for the rainfall differences derived from both datasets are discussed. Results show that GPCP and TRMM PR datasets present similar distribution patterns over the Tropics but with some differences in amplitude and location. Generally, the average difference over the ocean of about 0.5 mm d^-1 is larger than that of about 0.1 mm d^-1 over land. Results also show that GPCP tends to underestimate the monthly precipitation over the land region with sparse rain gauges in contrast to regions with a higher density of rain gauge stations. A Probability Distribution Function （PDF） analysis indicates that the GPCP rain rate at its maximum PDF is generally consistent with the TRMM PR rain rate as the latter is less than 8 mm d^-1. When the TRMM PR rain rate is greater than 8 mm d^-1, the GPCP rain rate at its maximum PDF is less by at least 1 mm d^-1 compared to TRMM PR estimates. Results also show an absolute bias of less than 1 mm d^-1 between the two datasets when the rain rate is less than 10 mm d^-1. A large relative bias of the two datasets occurs at weak and heavy rain rates.     

The Structure and Rainfall Features of Tropical Cyclone Rammasun （2002）

Tropical Rainfall Measuring Mission (TRMM) data [TRMM Microwave Imager/Precipitation Radar/Visible and Infrared Scanner (TMI/PR/VIRS)] and a numerical model are used to investigate the structure and rainfall features of Tropical Cyclone (TC) Rammasun (2002). Based on the analysisof TRMM data, which are diagnosed together with NCEP/AVN [Aviation (global model)] analysis data,some typical features of TC structure and rainfall are preliminary discovered. Since the limitations of TRMM data are considered for their time resolution and coverage, the world observed by TRMM at several moments cannot be taken as the representation of the whole period of the TC lifecycle, therefore the picture should be reproduced by a numerical model of high quality. To better understand the structure and rainfall features of TC Rammasun, a numerical simulation is carried out with mesoscale model MM5 in which the validations have been made with the data of TRMM and NCEP/AVN analysis.     

登陆台湾岛热带气旋强度和结构变化的统计分析

利用1949—2008年共60年的《台风年鉴》、《热带气旋年鉴》资料及CMA-STI热带气旋最佳路径数据集,2001—2008年美国联合台风警报中心(JTWC)热带气旋尺度相关资料及日本气象厅(JMA)的TBB资料,统计分析西北太平洋(包括南海)热带气旋(TC)在登陆台湾过程中强度和结构变化的基本特征,主要结论有:(1)TC登陆台湾时强度为台风及以上级别的样本数占总样本数约60%,主要出现在6—9月,东部登陆TC的强度一般比在西部登陆的强;(2)大部分TC在岛上维持6 h左右,登陆时最大风速≤5级和强度为超强台风的TC穿越台湾岛时移动比较缓慢;(3)126个登陆台湾的TC样本过岛后近中心海平面气压平均增加5.61 hPa,近中心最大风速平均减小3.58 m/s,在台湾东部地区登陆TC的衰减率比在西部登陆的大3倍左右;(4)TC在登陆台湾前6 h至离岛后6 h期间其8级和10级风圈半径均明显减小,TC形状略呈长轴为NE-SW向的椭圆状,而其最大风速的半径却逐渐增大;(5)TBB分析结果显示,TC登陆台湾前,其外围对流主要出现在南侧和西侧,结构不对称,登陆以后,TC北部及东部的对流显著发展,外围结构区域对称;但中心附近的强对流则从登陆前6 h开始逐渐减弱消失。表明TC穿越台湾过程中内核结构松散、强度减弱。     

1949—2009年西北太平洋热带气旋气候特征

利用1949—2009年中国气象局热带气旋（TC:Tropical Cyclone）最佳路径数据集,对西北太平洋TC生成源地的时空分布、生成和登陆我国TC的年、月频数分布、强度分布和地理分布等气候特征进行统计分析。研究结果表明：在这61年中生成的TC呈减少趋势,登陆我国的TC数量比较稳定,不过近10年来登陆的较强TC数量却呈现出上升趋势;每年6—10月是TC高发期,强度等级越高的TC生成季节越偏晚,而8月是生成和登陆数量最多的月份;TC平均生命期随强度等级的增加而增大,且逐渐表现出单峰值分布特征;TC频数的地理分布以我国南海和菲律宾以东洋面为中心,向四周呈辐射状减少,近10年来其活动范围有所西伸加强。     

0302号(鲸鱼)台风降水和水粒子空间分布的三维结构特征

由于缺乏关于台风结构信息的高分辨率资料,即探测台风云系内部结构特征的技术限制,造成了进一步理解台风的动力传送特征的困难.作者用热带测雨卫星(TRMM,Tropical Rainfall Measuring Mission)的测雨雷达(PR,Precipitation Radar)和TRMM微波图像仪(TMI,TRMM Microwave Imager)资料详细研究了"鲸鱼"台风(0302号)于2003年4月16日1105 UTC的降水和降水云系中各种水粒子的三维结构特征.通过分析发现该时刻:(1)台风降水中大部分区域为层性降水(占总降水面积的85.5%),对流性降水占总降水面积的13.1%,但对流性降水的贡献却达到41.8%,所以,虽然对流性降水所占面积比例很少,但是它对总降水量的贡献却很大.(2)60%降水主要集中在距离台风中心100 km以内的区域,约占总降水量的60%.(3)各种水粒子含量随着与台风中心距离的增加而减少.降水云系中水粒子最大含量出现高度与水粒子的种类和与台风中心的距离有关.最后,分析了台风降水和降水云系中三维分布的成因.     

Climatology of Tropical Cyclone Extreme Rainfall over China from 1960 to 2019

Tropical cyclone extreme rainfall(TCER)causes devastating floods and severe damage in China and it is therefore important to determine its long-term climatological distribution for both disaster prevention and operational forecasting.Based on the tropical cyclone(TC)best-track dataset and TC precipitation data from 1960 to 2019,the spatiotemporal distribution of TCER affecting China is analyzed.Results show that there were large regional differences in the threshold for TCER in China,decreasing from the southeastern coast to the northwest inland.TCER occurred infrequently in northern China but had a high intensity and was highly localized.The frequency and intensity of TCER showed slightly increasing trends over time and was most likely to occur in August(41.0%).Most of the TC precipitation processes with extreme rainfall lasted for four to six days,with TCER mainly occurring on the third to fourth days.TCER with wide areas showed a northwestward prevailing track and a westward prevailing track.Strong TCs are not always accompanied by extreme precipitation while some weak TCs can lead to very extreme rainfall.A total of 64.7%(35.3%)of the TCER samples occurred when the TC was centered over the land(sea).TCER≥250 mm was located within 3°of the center of the TC.When the center of the TC was located over the sea(land),the extreme rainfall over land was most likely to appear on its northwestern(northeastern)side with a dispersed(concentrated)distribution.TCER has unique climatic characteristics relative to the TC precipitation.     

A Technique of Rainfall Assimilation for Dynamic Extended Range Monsoon Prediction

Summary ?A methodology has been developed to assimilate satellite-measured rainfall during the initial phase of model integration for extended range monsoon prediction. The vertical profiles of latent heating corresponding to different rain rates have been derived from the model statistics. These heating rates have been assimilated through nudging in the thermodynamics equation of the model. This procedure of assimilating observed heating has corrected the simulation of heating location in the model and consequently removed the anomalous sinking motion over Indian landmass. With the correction of vertical circulation, both mean July rainfall over India and the distribution have improved. Interannual variability has been brought out for the years 1987 and 1988. In view of the availability of rainfall profile from Tropical Rain Measuring Mission (TRMM) there is a scope of adopting this method of assimilating observed rainfall, for extended range monsoon prediction. Received February 12, 1999/Revised May 4, 1999     

利用热带降雨测量卫星的微波成像仪观测资料反演陆地降水

利用热带降雨测量卫星的微波成像仪资料，结合淮河流域试验加密观测期的阜阳地面天 气雷达雨量资料，建立了以散射指数和极化订正温度为主要参数的降水反演算法。对文 中所做反演试验与日本ＮＡＳＤＡ用微波成像仪和星载测雨雷达反演的雨强进行了比较。结果表明 ，文中所用的方法在反演陆地下垫面的降雨强度的分布和降雨区域的确定是比较成功的。