中国地区降水持续性的季节变化特征

本文利用我国588个气象站1969-2008年逐12小时的降水资料,分析了中国地区降水持续性的空间分布特征及其季节演变规律。分析结果表明,35°N以南,西部和东部年平均的降水平均持续时间较长,中部略短;35°N以北,西北和内蒙西部最短,东北地区北部略长。将降水事件按持续时间分类自南向北,东南地区、江淮和黄淮地区、东北和华北北部地区短时降水（持续一个时次,12小时）的降水量和降水频率占全年总降水的比例逐渐增加,持续性降水（持续3个时次及以上）的比例减少。降水平均持续时间随季节的变化基本能反映出江南春雨、江淮梅雨、东北和华北夏季雨季、关中盆地和汉水谷地的秋雨以及青藏高原地区和西南地区夏季雨季。同时,东南地区秋冬季节、江淮和黄淮地区10月上旬和西南地区10月下旬存在降水平均持续时间的峰值,与降水量的变化不一致,是由持续性降水频率的增加和短时降水频率的减少造成的。此外,东部三个区域降水平均持续时间的夏季季节内变化对应了季风雨带的“北跳和南撤”过程。     

A study of influencing systems and moisture budget in a heavy rainfall in low latitude plateau in China during early summer

Analysis of a heavy rainfall in a lower latitude plateau and characteristics of water vapor transportation have been conducted by using conventional data and denser surface data. The results show： （1） the heavy rainfall was caused by a series of mesoscale systems under favorable large-scale conditions when the warm moister air and cold air interacted with each other. At the same time, the coupling between the upper- and lower-level jets was revealed. It is also found that there exists some different characteristics among the main influencing systems of heavy rainfalls in Yunnan, such as the Indian-Myanmar trough and the path of the cold air, compared with those in East and South China. （2） The interaction between mesoscale convergence lines near the ground may be a possible triggering mechanism for the occurrence of mesoscale systems, and the dynamical and thermal dynamical structure of the mesoscale systems was very obvious. The convergence lines may relate closely to the terrain of Yunnan, China. （3） The computation of the water vapor budget reveals that the primary source of water vapor supply for heavy rainfall was in the Bay of Bengal. In this case, the water vapor could be transported into Yunnan even though the amount of water vapor was less than that in the lower troposphere in East and South China. In addition, the analysis for three-dimensional air parcel trajectories better revealed and described the source location and the transportation of water vapor to Yunnan.     

中国暴雨的科学与预报：改革开放40年研究成果

总结了改革开放以来中国学者在暴雨科学与预报领域取得的重要研究进展和主要成果。其中,暴雨机理研究成果从重要天气系统、中国主要区域的暴雨、台风暴雨等3个方面分别进行综述,而暴雨预报技术研发与应用则从中国数值天气预报发展和暴雨预报客观方法两方面进行归纳。     

Large-scale Circulation Anomalies Associated with Interannual Variation in Monthly Rainfall over South China from May to August简

Interannual variation in summer rainfall over South China （SC） was investigated on the monthly timescale.It was found that monthly rainfall from May to August exhibits different features of variation,and the amounts are basically independent of each other.There is a significant negative correlation,however,between May and July SC rainfall,which is partially related to the developing phases of ENSO events.It was also found that stronger （weaker） lower-tropospheric winds over SC and the upstream parts are responsible for more （less） SC rainfall in every month from May to August.Despite this monthly consistent enhancement of horizontal winds,the wind anomalies exhibit distinct differences between May-June and July-August,due to the remarkable change in climatological winds between these two periods.More SC rainfall is associated with a lower-tropospheric anticyclonic anomaly over the SCS and the Philippine Sea in May and June,but with a cyclonic anomaly centered over SC in July and August.     

中国东南部地区4-6月强降水的低频变化特征

利用全国2 400多台站逐日降水资料,分析了中国东南部地区4—6月10~30 d低频强降水的时空变化特征。结果表明:4—6月10~30 d低频强降水的方差大值区在中国的长江及其以南地区,中心位于江南的中东部,东南部地区4—6月10~30 d低频强降水距平的第一模态反映该区域呈一致变化。功率谱分析表明第一模态时间变化的周期以10~30 d低频分量为主。根据区域强降水及其10~30 d低频强降水、区域强降水正交经验函数(EOF)分析的第一模态时间系数(PC1)及PC1的10~30 d低频分量的年际方差,结合它们两两之间逐年的相关系数,确定了区域强降水10~30 d强振荡典型年份。对典型年降水异常分布的方差分析,表明强振荡年区域总降水量异常主要是由10~30 d强降水的低频变化引起的。     

Moisture transport over the Arabian Sea associated with summer rainfall over Pakistan in 1994 and 2002

In this study,we aimed to elucidate the critical role of moisture transport affecting monsoon activity in two contrasting summers over the Arabian Sea during the years 1994,a relatively wet year,and 2002,a relatively dry year.A comprehensive diagnostic evaluation and comparisons of the moisture fields were conducted;we focused on the precipitation and evaporation as well as the moisture transport and its divergence or convergence in the atmosphere.Monthly mean reanalysis data were obtained from the National Centers for Environmental Prediction(NCEP-I and-II).A detailed evaluation of the moisture budgets over Pakistan during these two years was made by calculating the latent energy flux at the surface(E P) from the divergence of the total moisture transport.Our results confirm the moisture supply over the Arabian Sea to be the major source of rainfall in Pakistan and neighboring regions.In 1994,Pakistan received more rainfall compared to 2002 during the summer monsoon.Moisture flow deepens and strengthens over Arabian Sea during the peak summer monsoon months of July and August.Our analysis shows that vertically integrated moisture transport flux have a significant role in supplying moisture to the convective centers over Pakistan and neighboring regions from the divergent regions of the Arabian Sea and the Bay of Bengal.Moreover,in 1994,a deeper vertically integrated moisture convergence progression occurred over Pakistan compared to that in 2002.Perhaps that deeper convergence resulted in a more intense moisture depression over Pakistan and also caused more rainfall in 1994 during the summer monsoon.Finally,from the water budget analysis,it has been surmised that the water budget was larger in 1994 than in 2002 during the summer monsoon.     

太行山地形对华北暴雨影响的数值模拟试验

利用高分辨率区域气候模式RegCM3对华北地区1996年夏季降水进行了数值模拟,对照中国台站的实测资料,对模拟的夏季降水量日变化特征进行了比较,在此基础上,设计了太行山地形敏感性试验,模拟了太行山脉地形高度变化对1996年夏季发生在华北地区的3次典型暴雨过程的影响.研究结果认为,RegCM3模式能够较好地模拟1996年夏季华北地区雨带位置及主要降水过程,对3次典型暴雨过程中暴雨中心的落区及位置移动均有较好的表现,不足的是模拟的降水量偏大.地形敏感性试验结果发现,太行山地形对华北暴雨天气过程有着重要影响,但是对于不同型态的暴雨过程,地形的影响有不同表现.对于太行山区型暴雨,太行山地形的阻挡和抬升作用导致迎风坡和背风坡降水增加,而去掉地形后太行山两侧降水明显减少;对于回流型暴雨,降水系统从东北地区南部向西南方向移动,低层气流主要为偏东型气流,地形的存在对于降水系统的西移速度及降水落区均有重要影响,去掉地形后太行山东侧降水明显减少;对于东移型暴雨,降水从太行山南麓向东北方向移动,太行山脉对于环流形势的影响并不明显,因而仅影响降水强度,对降水位置影响不大.     

Seasonal prediction of June rainfall over South China: Model assessment and statistical downscaling

The performances of various dynamical models from the Asia-Pacific Economic Cooperation(APEC) Climate Center(APCC) multi-model ensemble(MME) in predicting station-scale rainfall in South China(SC) in June were evaluated.It was found that the MME mean of model hindcasts can skillfully predict the June rainfall anomaly averaged over the SC domain.This could be related to the MME's ability in capturing the observed linkages between SC rainfall and atmospheric large-scale circulation anomalies in the Indo-Pacific region.Further assessment of station-scale June rainfall prediction based on direct model output(DMO) over 97 stations in SC revealed that the MME mean outperforms each individual model.However,poor prediction abilities in some in-land and southeastern SC stations are apparent in the MME mean and in a number of models.In order to improve the performance at those stations with poor DMO prediction skill,a station-based statistical downscaling scheme was constructed and applied to the individual and MME mean hindcast runs.For several models,this scheme can outperform DMO at more than 30 stations,because it can tap into the abilities of the models in capturing the anomalous Indo-Paciric circulation to which SC rainfall is considerably sensitive.Therefore,enhanced rainfall prediction abilities in these models should make them more useful for disaster preparedness and mitigation purposes.     

华南夏季12-30 d持续性强降水的低频特征分析

利用1982-2011年夏季（5-8月）中国气象观测站点逐日降水资料、NCEP/NCAR逐日再分析资料、NOAA逐日向外长波辐射和海表温度资料集,通过选取低频降水事件的方法,分析了华南夏季12-30 d持续性强降水事件的基本特征,然后利用位相合成法对持续性强降水期间伴随的低频大气环流型以及低频信号的来源和传播情况进行研究,同时也分析了低频海-气耦合过程对持续性强降水的影响。结果表明：（1）华南夏季降水具有显著的12-30 d低频振荡特征,持续性强降水事件在6月发生次数最多,低频降水期间的雨带自东南向西北传播。（2）在持续性强降水发生期间,华南及邻近海域低层受强大的低频气旋式环流控制,低频上升运动显著,而中国南海-菲律宾海一带则是强的低频反气旋式环流,其西侧向北的低频水汽输送不断将中国南海的水汽送至华南及邻近海域进行辐合上升。低层的低频信号来源于热带西太平洋和中国南海-菲律宾海一带低频振荡的西北向传播,同时伴随着西太平洋副热带高压明显的西伸东退过程。（3）在高层,华南北侧（22°-45°N,95°-130°E）区域强大的低频气旋式环流和孟加拉湾-中国南海一带的低频反气旋式环流相互配合,使华南高层处于强大的辐散环境中,从而加强了华南低层的辐合与低频上升运动,造成持续性强降水的增强。高层的低频信号来源于低频罗斯贝波列的东南向传播。（4）低频大气环流异常通过云辐射和热通量过程改变低频海表温度异常,而由大气强迫的低频海表温度异常通过影响低层大气的稳定性来对大气施加明显的反馈作用,该海-气耦合过程有利于大气低层低频信号向华南地区传播,从而影响了华南持续性强降水的发生、发展与结束。     

华南前汛期暖区暴雨研究新进展

华南前汛期暖区暴雨一直是困扰科研和业务的重要难题。在1970s末第一次华南暴雨综合试验中,老一辈科学家提出了华南前汛期暖区暴雨的概念,并揭示了诸多对华南暴雨研究有重要意义的成果。近年来,随着现代气象探测手段、高性能计算能力的提升以及中尺度暴雨科学观测试验的开展,对华南前汛期暖区暴雨的研究取得了不少新的认识。本文重点梳理了近10 a有关华南前汛期暖区暴雨方面的最新研究进展,从暖区暴雨的定义及分类、多尺度天气特征、形成机制及可预报性研究等4个方面进行系统性论述。最后,对华南前汛期暖区暴雨研究存在的问题、未来发展方向进行了简要的讨论和展望。     

江淮流域夏季持续性强降水的低频特征分析

利用1979-2009年夏季(6-8月)中国气象观测站点逐日降水资料、NCEP/NCAR的再分析资料以及向外长波辐射资料等,选取低频降水事件来表征江淮流域夏季持续性强降水,然后分析其基本特征及伴随的低频大气环流形势,利用位相合成的方法对该低频信号的来源和传播特征进行研究.结果表明:江淮流域夏季持续性强降水在6-7月份发生次数较多;在持续性强降水期间,江淮流域低层受低频气旋控制,南海至菲律宾海一带则是很强的低频反气旋,该低频反气旋西侧,向北的低频水汽输送将水汽不断送至江淮流域形成辐合;与持续性强降水相关联的850 hPa上的低频信号,来源于黄河河套地区低频振荡的东南向传播和西北太平洋上空低频振荡的西北向传播;在高层,当持续性强降水发生时,江淮流域的西北侧(37.5°N,80 ～100°E)附近为强烈的低频气旋式环流,紧邻该环流的西北侧,则是一个低频反气旋,两者同南海—菲律宾海一带的低频反气旋构成了一个西北—东南向的低频波列;西太平洋副热带高压和南亚高压在持续性强降水期间表现出了显著的相向而行、相背而去的特征.     

北京地区两次极端特大暴雨过程中短时强降水环境条件对比分析

针对北京地区2012年7月21日(简称“7.21”过程)和2016年7月20日(简称“7.20”过程)极端特大暴雨中的短时强降水,对短时强降水实况、环流形势、地形影响及环境的动力、水汽和热力条件进行了分析,并结合较长时段的历史资料,从单点和区域角度对环境动力、水汽和潜在热力条件的极端性进行了对比分析。结果表明:(1)尽管两次过程中的短时强降水实况差异显著,但均出现在非常有利的天气形势下。(2)针对短时强降水环境的单点动力、水汽和热力条件对比显示,两次过程中的850 hPa动力抬升和整层可降水量(PWAT)均极端偏强,但抬升指数(LI)表征的热力条件差异差别巨大,2012年“7.21”过程中为偏强,2016年“7.20”过程中为偏弱。(3)针对长时间序列资料的标准化偏差异常(SD)显示,两次过程中850 hPa风场和PWAT的SD均超过了3σ,为极端偏强,LI表征的潜在热力条件方面,2012年“7.21”过程中低于-1σ,2016年“7.20”过程中与历史同期持平,表明热力条件的差异是导致两次极端暴雨过程中短时强降水强度巨大差异的重要原因。     

2010年7月31日吉林省东南部短时强降水过程分析

利用吉林省加密站实时观测资料、NCEP 1°×1°再分析资料和吉林省白山观测站多普勒雷达等资料,对2010 年7月31日吉林省东南部的短时强降水天气过程进行初步分析。结果表明：500hPa平直锋区上短波扰动出现往往伴随强对流天气的发生;上冷下暖的热力垂直结构有利于低层辐合抬升;当风场引起的辐合抬升仅存在于底层时降水不会发生,故更需关注整层风场的结构变化;强降水水汽来自于暴雨区前期降水的积累,缺外来水汽的持续输送是此次强降水历时短的主要原因之一;小股冷空气入侵高温高湿气团是导致不稳定能量释放的主要原因,强降水落区对应于冷空气侵入高能区位置,强降水时段对应K指数由极大值减小的过程;多普勒雷达资料中雷达回波的强度和缺口、径向速度的强度和零线形状、以及逆风区对预报短时强降水具有很好的指示意义。     

The Persistent Heavy Rainfall over Southern China in June 2010：Evolution of Synoptic Systems and the Effects of the Tibetan Plateau Heating

This study investigates influencing weather systems for and the effect of Tibetan Plateau （TP）’s surface heating on the heavy rainfall over southern China in June 2010, focusing on the four persistent heavy rainfall events during 14-24 June 2010. The ma jor weather systems include the South Asian high, midlatitude trough and ridge, western Pacific subtropical high in the middle troposphere, and shear lines and eastward-moving vortices in the lower troposphere. An ensemble of convection-permitting simulations （CTL） is carried out with the WRF model for these rainfall events, which successfully reproduce the observed evolution of precipitation and weather systems. Another ensemble of simulations （SEN） with the surface albedo over the TP and its southern slope changed artificially to one, i.e., the surface does not absorb any solar heating, otherwise it is identical to CTL, is also performed. Comparison between CTL and SEN suggests that the surface sensible heating of TP in CTL significantly affects the temperature distributions over the plateau and its surroundings, and the thermal wind adjustment consequently changes atmospheric circulations and properties of the synoptic systems, leading to intensified precipitation over southern China. Specifically, at 200 hPa, anticyclonic and cyclonic anomalies form over the western and eastern plateau, respectively, which enhances the southward cold air intrusion along the eastern TP and the divergence over southern China;at 500 hPa, the ridge over the northern plateau and the trough over eastern China are strengthened, the southwesterly flows along the northwestern side of the subtropical high are intensified, and the positive vorticity propagation from the plateau to its downstream is also enhanced significantly;at 850 hPa, the low-pressure vortices strongly develop and move eastward while the southwesterly low-level jet over southern China strengthens in CTL, leading to increased water vapor convergence and upward motion over the precipitation region.     

天津市夏季降水日变化特征

利用1954－2007年天津市夏季逐时自记降水资料,分析了天津市夏季降水（包括逐小时降水量、降水频次、降水强度以及不同持续时间降水）日变化规律。结果表明：天津市一日内不同时次的多年累积降水量具有显著的日变化特征,呈明显的双峰型,高值分别出现在午后17时和午夜02时。逐小时降水强度与降水量的变化特征非常一致,而多年累积降水频次在凌晨02时至08时较高,之后至11时逐步降低,11时至24时变化不大。降水量与降水频次及降水强度的关系均达到显著性水平（P < 0.001）,但逐小时降水强度与降水量相关性明显高于降水频次,表明降水量变化与降水强度有直接的关系,而降水频次对累积降水量的贡献占较小的权重。持续不同时间降水事件的发生次数在一日内的变化特征明显不同,长时性降水峰值集中在清晨,而短时性降水尤其是1-3 h降水主要以午后为主。     

华南暖区暴雨中一次飑线的中尺度分析

利用地面加密观测资料、高空观测资料、多普勒雷达观测和雷达风场反演资料等,分析造成2010年5月6—7日华南暴雨中一次飑线的演变过程及三维结构特征。结果表明:(1)此次飑线过程发生于200 hPa高空辐散区、500 hPa高空槽后、地面准静止锋锋前暖区内,850 hPa飑线北侧为切变线,东南侧存在低空急流,中低层为中等强度垂直风切变。(2)该飑线系统初始对流单体由西风受广西大瑶山脉地形阻挡而触发。发展过程中两广交界处不断生成新单体,东移发展并入对流带,单体发展及对流带的形成与地面中尺度辐合线关系密切。(3)该飑线在形成过程中存在对流带与对流单体的锢囚过程,锢囚过程中地面辐合线及中层中气旋起组织作用,至盛期对流带东段出现弓形回波结构。强降水拖曳、雨滴蒸发冷却增强下沉气流及中层冷空气入流,造成地面冷池及后部辐散出流,促进弓形回波发展。(4)成熟期飑线系统包含弓形回波、冷池及不明显的层状云区,三维结构特征与经典飑线类似,但无涡旋对,雷暴高压也不明显。     

两个典型ENSO季节演变模态及其与我国东部降水的联系

本文根据1950~2014年月平均海温和大气环流资料以及中国160站降水等资料,利用扩展经验正交函数（EEOF）分析、相关分析以及合成分析等方法,分析了太平洋海温季节演变的主导模态,并探讨了各模态与中国东部降水和东亚环流季节变异的关系及其联系的物理过程。结果表明,ENSO（El Ni?o/Southern Oscillation）季节演变存在2个主导模态,包含4种类型:El Ni?o持续型、La Ni?a持续型、La Ni?a转El Ni?o型和El Ni?o转La Ni?a型。发现不同模态和类型的ENSO季节变化过程我国东部降水距平的分布和强度都有明显差异。El Ni?o持续型和El Ni?o转La Ni?a型,冬春季和初夏均处在El Ni?o背景下,降水异常分布存在一定共性,但盛夏和秋季分别受El Ni?o和La Ni?a影响,降水异常分布差异十分明显,前者雨带北跳慢、位置偏南而后者雨带北跳快、位置偏北。La Ni?a持续型和La Ni?a转El Ni?o型也是如此,冬春季和初夏降水异常分布大致相似,但盛夏和秋季分别受La Ni?a和El Ni?o影响,前者雨带北跳快、位置偏北而后者雨带北跳慢、位置偏南。因此,利用ENSO做我国降水的气候预测时,不能只着眼于前期冬季El Ni?o或La Ni?a事件,还应考虑其未来演变所属的可能模态和类型。对他们之间联系的物理过程分析表明,不同ENSO季节演变模态和类型主要通过影响西太平洋副热带高压以及西风带经向型/纬向型环流调整及伴随的低纬暖湿水汽输送以及中高纬冷空气活动变化来影响我国东部降水。其中,西太平洋菲律宾群岛附近异常反气旋（或气旋）、赤道Walker环流和北半球Hadley环流分别是联系ENSO与西太平洋副热带高压活动和东亚西风带经向型/纬向型环流的重要环节。     

江南春雨雨日的变化及其与欧亚大陆积雪的联系

利用中国气象局提供的1960—2019年江南区站点观测逐日降水数据,分析了江南春雨不同持续时长雨日的变化及其与欧亚大陆积雪的联系。结果表明,江南春雨以持续5 d及以上的长持续降水为主,但降水日数下降趋势明显,导致长持续降水减少。利用奇异值分解法(Singular Value Decomposition,SVD)发现,欧亚大陆3—5月积雪覆盖率与江南春雨雨日数有显著正相关关系。将(48°~59°N,90°~110°E)区域平均积雪覆盖率定义为积雪覆盖指数,通过指数与同期大气环流的回归分析发现,当积雪偏少时,我国中北部及西伯利亚地区500 hPa位势高度正异常,在江南区850 hPa风场和水汽通量场西南向负异常,导致江南春雨雨日数减少。合成分析进一步验证了积雪偏少会在江南区形成异常东北风抑制水汽输送至江南地区,不利于降水发生。     

一次大气河背景下华北地区暴雨的诊断分析

利用2018年5月15-16日的ERA5再分析资料和观测资料,对大气河背景下一次华北地区暴雨过程的天气形势、大气河在暴雨过程中的作用及其在暴雨前后的演变特征以及结构特征进行了诊断分析.结果 表明此次降水过程的直接影响系统是位于华北地区的高空槽、低空切变线、地面冷锋和高低空急流,这些系统使得华北地区低层辐合高层辐散,带来...