江苏不同强度降雨对能见度影响分析

利用江苏70个基本站多年逐时雨量、相对湿度、风向、风速以及同时段内最低能见度等观测资料,分析不同强度降雨对能见度的影响,并对比分析两种不同强度降雨造成的低能见度事件统计特征。结果表明:降雨是除雾以外,江苏低能见度的主要影响天气(14. 7%),其中稳定性弱降雨和短时强降雨影响最大。与低能见度雾事件不同,降雨造成的低能见度事件全天各时段均可能出现,发生时可伴随较强的风速(2 m/s),短强低能见度多见风速4 m/s(26. 6%)。江苏冬春两季为雨雾高发季,主要受降雨持续时间影响,对应的低能见度区间为500~1 000 m,有明显日变化。短强低能见度主要受雨强影响,多发生于6—9月,对应的低能见度区间为小于200 m,无明显日变化。两种降雨产生的低能见度事件有明显的空间分布差异,且雨雾低能见度发生时偏北风占主导,短强低能见度发生时则偏东风占主导。     

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。     

湖南夏季降水日变化特征

利用湖南96个测站13年的逐时自记降水资料, 分析了夏季（6~8月）降水日变化特征。结果表明, 湖南夏季降水日变化呈现显著的区域差异。湘东南降水量、 降水频次峰值主要出现在午后到傍晚, 而其它地区的降水峰值一般出现在清晨。进一步分析显示, 降水频次峰值出现时次分布更集中, 区域特征更鲜明。湘西北、 湘东南区域平均的累积降水量、 降水频次及降水强度的日变化在清晨和午后均呈双峰型特征。湘西北主（次）峰值出现的时间大致与湘东南次（主）峰值出现的时间对应。同时, 降水日变化与降水持续时间密切相关。持续5~10 h降水事件是持续1~4 h事件与持续10 h以上事件降水量峰值出现时间发生显著变化的过渡降水事件。持续1~4 h（10 h以上）的降水事件的极值降水始发时间为午后至傍晚（夜间）。在不同持续时间的降水事件中, 持续2 h降水的累积量最大。     

Daily rainfall trend in the Valencia Region of Spain

Summary ?We have analyzed daily rainfall trends throughout the second half of the 20^th century in the western Mediterranean basin (Valencia Region, E of Spain). The area is characterized by high torrentiality, and during the second half of the 20^th century some of the highest daily rainfall values in the Mediterranean basin have been recorded. In this area, mean annual rainfall varies between 500 and 300 mm and is overwhelmingly dependent on just a few days of rain. Daily maximum rainfall varies on average from 120 mm day⁻¹ to 50 mm day⁻¹, and represents a mean of 17% (coastland) to 9% (inland) of annual rainfall. The 10 days in each year with the heaviest rainfall (called “higher events”) provide over 50% of the annual rainfall and can reach more than 400 mm on average. We compared the annual rainfall trend and the trend of higher and minor events defined by percentiles, both in volume and variability. We, therefore, tested whether annual rainfall changes depend on the trend of the higher (rainfall) events. To overlap spatial distribution of trends (i.e.: positive, no significant and negative trends) we have used cross-tab analysis. The results confirm the hypothesis that annual rainfall changes depend on changes found in just a few rainy events. Furthermore, in spite of their negative trend, higher events have increased their contribution to annual rainfall. As a consequence, although torrential events may have diminished in magnitude, future scenarios seem to be controlled by a limited number of rainy events which will become more and more variable year on year. The high spatial density of data used in this work, (97 observatories per 24.000 km², overall mean 1 observatory per 200 km²), suggests to us that extreme caution should be applied when analyzing regional and sub-regional changes in rainfall using GCM output, especially in areas of high torrentiality. Received August 1, 2002; revised November 11, 2002; accepted December 1, 2002 Published online May 19, 2003     

Progress in Studies of the Precipitation Diurnal Variation over Contiguous China

This paper summarizes the recent progress in studies of the diurnal variation of precipitation over con- tiguous China. The main results are as follows. （1） The rainfall diurnal variation over contiguous China presents distinct regional features. In summer, precipitation peaks in the late afternoon over the south- ern inland China and northeastern China, while it peaks around midnight over southwestern China. In the upper and middle reaches of Yangtze River valley, precipitation occurs mostly in the early morning. Summer precipitation over the central eastern China （most regions of the Tibetan Plateau） has two diurnal peaks, i.e., one in the early morning （midnight） and the other in the late afternoon. （2） The rainfall diurnal variation experiences obvious seasonal and sub-seasonal evolutions. In cold seasons, the regional contrast of rainfall diurnal peaks decreases, with an early morning maximum over most of the southern China. Over the central eastern China, diurnal monsoon rainfall shows sub-seasonal variations with the movement of summer monsoon systems. The rainfall peak mainly occurs in the early morning （late afternoon） during the active （break） monsoon period. （3） Cloud properties and occurrence time of rainfall diurnal peaks are different for long- and short-duration rainfall events. Long-duration rainfall events are dominated by strat- iform precipitation, with the maximum surface rain rate and the highest profile occurring in the late night to early morning, while short-duration rainfall events are more related to convective precipitation, with the maximum surface rain rate and the highest profile occurring between the late afternoon and early night. （4） The rainfall diurnal variation is influenced by multi-scale mountain-valley and land-sea breezes as well as large-scale atmospheric circulation, and involves complicated formation and evolution of cloud and rainfall systems. The diurnal cycle of winds in the lower troposphere also contributes to the regional differences     

中国大陆降水日变化研究进展

文章概述了中国大陆降水日变化的最新研究成果,给出了中国大陆降水日变化的整体图像,指出目前数值模式模拟降水日变化的局限性,为及时了解和掌握降水日变化研究进展、开展相关科学研究和进行降水预报服务提供了有价值的科学依据和参考。现有研究表明：（1）中国大陆夏季降水日变化的区域特征明显。在夏季,东南和东北地区的降水日峰值主要集中在下午;西南地区多在午夜达到降水峰值;长江中上游地区的降水多出现在清晨;中东部地区清晨、午后双峰并存;青藏高原大部分地区是下午和午夜峰值并存。（2）降水日变化存在季节差异和季节内演变。冷季降水日峰值时刻的区域差异较暖季明显减小,在冷季南方大部分地区都表现为清晨峰值;中东部地区暖季降水日变化随季风雨带的南北进退表现出清晰的季节内演变,季风活跃（间断）期的日降水峰值多发生在清晨（下午）。（3）持续性降水和局地短时降水的云结构特性以及降水日峰值出现时间存在显著差异。持续性降水以层状云特性为主,地表降水和降水廓线的峰值大多位于午夜后至清晨;短时降水以对流降水为主,峰值时间则多出现在下午至午夜前。（4）降水日变化涉及不同尺度的山-谷风、海-陆风和大气环流的综合影响,涉及复杂的云雨形成和演变过程,对流层低层环流日变化对降水日变化的区域差异亦有重要影响。（5）目前数值模式对中国降水日变化的模拟能力有限,且模拟结果具有很强的模式依赖性,仅仅提高模式水平分辨率并不能总是达到改善模拟结果的目的,关键是要减少存在于降水相关的物理过程参数化方案中的不确定性问题。     

Fluctuations in annual cycles and inter-seasonal memory in West Africa: rainfall, soil moisture and heat fluxes

Summary Annual cycle and inter-seasonal persistence of surface-atmosphere water and heat fluxes are analyzed at a 5-day time step over the West African Monsoon (WAM) through observational precipitation estimates (CMAP), model datasets (NCEP/DOE level 2 reanalyses) and a Soil Water Index (SWI) from the ERS scatterometer. Coherent fluctuations (30–90 days) distinct from supra-synoptic variability (10–25 day periods) are first detected in the WAM precipitation and heat fluxes over the period 1979–2001. During all the northward excursion of the WAM rain band, a succession of four active phases (abrupt rainfall increases) occurs. They are centered in the first days of March, mid-April, the second half of May and from the last week of June to mid-July (the Sahelian onset). A simple statistical approach shows that the Spring to Summer installation of the monsoon tends to be sensitive to these short periods. Other analyses suggest the existence of lagged relationship between rainfall amounts registered in successive Fall, Spring (active periods) and Summer (top of the rainy season) implying land surface conditions. The spatial extension of the generated soil moisture anomalies reaches one maximum in March, mainly at the Guinean latitudes and over the Sahelian belt where the signal can persist until the next monsoon onset. Typically after abnormal wet conditions in September–October two signals are observed: (1) more marked fluctuations in Spring with less (more) Sahelian rainfall in May (June and after) at the Sahelian-Sudanian latitudes; (2) wetter rainy seasons along the Guinean coast (in Spring and Summer with an advance in the mean date of the ‘little dry season’). The reverse arises after abnormal dry conditions in autumn.     

基于小时降水资料研究广东省降水分布特征

基于2001-2018年广东省86个国家自动气象站逐小时降水资料,分析了广东省不同历时降水的时空分布特征.结果表明：1）除粤北山区外,基本符合年均降水时数越多,累积降水量越大的规律.年均小时降水强度从南部沿海向北部内陆呈减弱趋势.2）汛期降水事件以短历时为主,占全年降水事件65.3%;累积降水量上,长历时降水量占汛期56.7%.前汛期短历时降水多发生在粤西;中历时降水多发生在珠三角两侧和粤西北地区;长历时降水多发生在粤东和粤北地区.后汛期短历时降水多发生在内陆,出现频次自西北向东南递减;中历时降水分布不均;长历时降水多发生在沿海.3）汛期降水时数日变化呈双峰型变化特征,小时降水强度日变化呈单峰型变化特征.小时降水强度峰值易出现在下午的站点多分布在内陆,小时降水强度峰值易出现在下半夜至上午时段的站点则多分布在沿海、部分山区和珠三角地区.     

Diurnal Variation of Southwest Monsoon Rainfall at Indian Stations

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基于小时降水资料研究北京地区降水的精细化特征

根据北京全区2007~2014年117个自动气象站逐小时降水资料,在揭示降水总体时空特征的基础上,进一步研究了北京地区各季（以春、夏、秋为主）降水的精细化特征。研究发现:北京全区年均降水量存在两个高值中心（城区和下风方向的降水高值中心）,城市热岛效应可能是城区高值中心形成的重要影响因素之一;北京全区降水的季节分布不均,日分布也不均匀;城市化对北京地区降水的影响具有季节差异,夏季短历时和中历时降水在城区和东北部存在显著的大值区,受到城市热岛效应的影响可能较为明显,长历时降水在城区反而相对偏低,而春季城区短、中历时降水并未偏多,长历时降水却在城区出现明显的高值中心;降水日变化季节差异明显,春、秋两季呈现双峰型变化,而夏季呈现单峰型变化,该日变化的特征与全区降水的空间分布格局关系紧密。     

近30 a江苏夏季降水日变化的气候学特征

基于1980—2013年江苏省61站小时降水资料,分析了江苏省夏季降水日变化的特点及小时极端降水、不同级别雨日的日变化特征。结果表明,江苏省夏季降水日变化具有显著的双峰分布特征,然而江苏省北部和南部降水的主峰时段并不一致。从降水频次、累积降水量来看,江苏省北部降水以清晨至早上时段为主峰、午后至傍晚时段为次峰,南部降水与之相反。长持续性降水占夏季降水的2/3左右,且江苏北部占比多于南部,均为清晨至早上的单峰分布;短持续性降水占夏季降水的1/3,在江苏北部呈现出以午后至傍晚为主峰,清晨至早上为次峰的双峰分布,而在江苏南部呈现出以午后至傍晚的单峰分布特点。小时极端降水,阈值分布南低北高,虽然频次较少,但占夏季降水的40%左右。小时极端降水日变化的双峰分布和夏季总体降水分布类似,但主峰大都出现在午后至傍晚。不同级别雨日的日变化分布各有不同,但全省各区无显著差异。累积降水量贡献主要来自于暴雨和大雨。暴雨无论是从降水频次、累积降水量还是降水强度都呈现清晨至早上的单峰分布。     

新疆东部黑戈壁地表辐射及能量收支演变特征

新疆东部黑戈壁作为气候恶劣、人迹罕至的生态脆弱区，具有丰富的太阳能资源。利用红柳河陆气相互作用观测站2019年4、7、9月观测资料，分析东疆黑戈壁地表辐射及能量收支演变特征。结果表明：（1）地表辐射及能量收支各分量日变化均为单峰型。就不同季节而言，太阳总辐射和净辐射为夏季>春季>秋季，反射短波辐射为春季>夏季>秋季，地表和大气长波辐射为夏季>秋季>春季。（2）能量收支各分量季节变化明显，感热通量为春季>夏季>秋季，潜热通量为夏季>秋季>春季，地表土壤热通量为秋季>夏季>春季；能量分配在不同季节均以感热为主，地表土壤热通量次之，潜热通量极其微弱。（3）地表反照率日变化均为“U”型，在不同季节表现为春季>秋季>夏季，依次为0.29、0.27、0.26。东疆黑戈壁地表反照率整体较高，这是下垫面为黑色砾石所致。     

Basic statistical characteristics of hourly rainfall amounts in Barcelona (Spain)

Summary In order to derive some statistical rainfall characteristics applicable to hydrology, data of continuous rainfall rate recordings of a Jardí gauge installed in Barcelona (Spain) have been converted to an hourly precipitation series. From these data, four useful distributions have been obtained and further compared with some theoretical models. It has been found that the duration of events is distributed exponentially. The duration of rainless intervals follow a generalized Pareto distribution, and the cumulative rainfall in the cumulative rain duration is beta distributed. Concerning the distribution of rain amounts, two models can be accepted, depending on the duration of the events. Comparison with a similar study carried out in Farnborough (United Kingdom) indicates that the events are shorter and that the amounts of rain collected in short events are larger in Barcelona.This work was supported by the DGICYT (Project NAT91-0596) and the CCE (Project PL 910104 Environment).With 7 Figures     

南海夏季风爆发前后华南前汛期降水日变化对比分析

利用华南地区248个国家级地面气象站逐小时降水数据和14个探空站数据,分析了2003—2016年4—6月华南前汛期降水日变化特征。据南海夏季风爆发时间,将降水分为爆发前后两个时段。华南地区主要存在两条大雨带,一个位于云贵高原至南岭山脉以南,另一个位于广东沿海地区。偏北雨带集中发生在后半夜至清晨时段,偏南雨带集中发生在中午至下午时段。南海夏季风爆发前后,降水量不存在明显相关性,相关系数较大时次位于中午至下午时段。前后期年降水标准差在0.5附近,变化幅度明显时段主要集中于凌晨至清晨。午后出现3 h多年降水量变化幅度最大值,最小时段为中午12时。降水量、降水频率和降水强度的经向分布特征明显且相似:降水量和降水频率在112 °E附近出现日变化转折,以西多出现不稳定夜雨,以东白天降水波动较大。在南海夏季风爆发前,降水特征主要表现为西部高频、南部高强,在清晨更多作用于对暴雨系统的增长;季风爆发后则表现为西北-东南南的高频率高强度降水形态,在傍晚更多作用于增加降水发生频率。      

Distribution and Diurnal Variation of Warm-Season Short-Duration Heavy Rainfall in Relation to the MCSs in China

Short-duration heavy rainfall（SDHR） is a type of severe convective weather that often leads to substantial losses of property and life. We derive the spatiotemporal distribution and diurnal variation of SDHR over China during the warm season（April–September） from quality-controlled hourly raingauge data taken at 876 stations for 19 yr（1991–2009）, in comparison with the diurnal features of the mesoscale convective systems（MCSs） derived from satellite data. The results are as follows. 1） Spatial distributions of the frequency of SDHR events with hourly rainfall greater than 10–40 mm are very similar to the distribution of heavy rainfall（daily rainfall 50 mm） over mainland China. 2） SDHR occurs most frequently in South China such as southern Yunnan, Guizhou, and Jiangxi provinces, the Sichuan basin, and the lower reaches of the Yangtze River, among others. Some SDHR events with hourly rainfall 50 mm also occur in northern China, e.g., the western Xinjiang and central-eastern Inner Mongolia. The heaviest hourly rainfall is observed over the Hainan Island with the amount reaching over 180 mm. 3） The frequency of the SDHR events is the highest in July, followed by August. Analysis of pentad variations in SDHR reveals that SDHR events are intermittent, with the fourth pentad of July the most active. The frequency of SDHR over mainland China increases slowly with the advent of the East Asian summer monsoon, but decreases rapidly with its withdrawal. 4） The diurnal peak of the SDHR activity occurs in the later afternoon（1600–1700 Beijing Time（BT））, and the secondary peak occurs after midnight（0100–0200 BT） and in the early morning（0700–0800 BT）; whereas the diurnal minimum occurs around late morning till noon（1000–1300 BT）. 5） The diurnal variation of SDHR exhibits generally consistent features with that of the MCSs in China, but the active periods and propagation of SDHR and MCSs difer in diferent regions. The number and duration of local maxima in the diurnal cycles of SDHR and MCSs also vary by region, with single, double, and even multiple peaks in some cases. These variations may be associated with the diferences in large-scale atmospheric circulation, surface conditions, and land-sea distribution.     

A new method to compare hourly rainfall between station observations and satellite products over central-eastern China

This study employs a newly defined regional-rainfall-event (RRE) concept to compare the hourly characteristics of warm-season (May-September) rainfall among rain gauge observations, China merged hourly precipitation analysis (CMPA-Hourly), and two commonly used satellite products (TRMM 3B42 and CMORPH). By considering the rainfall characteristics in a given limited area rather than a single point or grid, this method largely eliminates the differences in rainfall characteristics among different observations or measurements over central-eastern China. The results show that the spatial distribution and diurnal variation of RRE frequency and intensity are quite consistent among different datasets, and the performance of CMPA-Hourly is better than the satellite products when compared with station observations. A regional rainfall coefficient (RRC), which can be used to classify local rain and regional rain, is employed to represent the spatial spread of rainfall in the limited region defining the RRE. It is found that rainfall spread in the selected grid box is more uniform during the nocturnal to morning hours over central-eastern China. The RRC tends to reach its diurnal maximum several hours after the RRE intensity peaks, implying an intermediate transition stage from convective to stratiform rainfall. In the afternoon, the RRC reaches its minimum, implying the dominance of local convections on small spatial scale in those hours, which could cause large differences in rain gauge and satellite observations. Since the RRE method reflects the overall features of rainfall in a limited region rather than at a fixed point or in a single grid, the widely recognized overestimation of afternoon rainfall in satellite products is not obvious, and thus the satellite estimates are more reliable in representing sub-daily variation of rainfall from the RRE perspective. This study proposes a reasonable method to compare satellite products with rain gauge observations on the sub-daily scale, which also has great potential to be used in evaluating the spatiotemporal variation of cloud and rainfall in numerical models.     

四川地区短时强降水事件时空演变特征研究

利用四川地区自动气象站逐小时降水观测资料,分析了2010~2019年5~9月短时强降水事件24h累计降水量、频次和强度的时空分布特征,探讨了短时强降水事件发生的频次、极值分布及其与地形、海拔高度等的关系。结果表明:四川地区平均24h累计降雨量基本在50mm以上,盆地东北部、西南部、南部及阿坝州东部甚至超过100mm,最大值出现在广安,达175mm。四川地区短时强降水事件开始时间的日变化特征表现为“V”型结构的夜间峰值位相,事件持续时段多为傍晚至凌晨,时长可达10h以上,最长甚至可持续22h。在强降水事件极值的日变化上,极大值频次和降水量呈单峰结构,在03时达到最大,其后逐渐减小至15时达到谷值,而后再次增大;降水强度呈弱双峰结构,分别在04时和16时达到谷值,13时和18时达到峰值,其日变化呈“增-减-增-减”的特征。四川短时强降水事件与复杂地形有密切的关系,5~6月事件活跃区在四川盆地中部,7月在盆地西部的龙门山脉一带,8月在雅安、乐山附近,9月在盆地北部且频次明显减少;短时强降水事件的最大小时雨强可达80mm以上,出现在7~8月的盆地西部龙门山一带和南部地区。短时强降水事件随着海拔高度的增加,发生频次和日数逐渐减少,海拔2000m以上地区基本无强降水发生日出现( 峨眉山气象站例外)。      

伊宁市1991-2011年降雨特征分析

利用1991～2011年5～9月伊宁市气象站逐小时降水资料,分析了伊宁近21a降雨特征。结果表明,21a来伊宁雨日年际变化较为明显,后10a和前10a相比,中雨、大雨和暴雨日数均出现增加,但小雨日数明显减少导致总雨日出现了减少。小雨过程发生最多的时段是7月中旬,中雨和大雨过程最多时段同在5月下旬。前半夜为中雨、大雨、暴雨过程最易发生时段,后半夜为小雨过程最易发生时段。逐小时降水量和降水频次呈现较为一致的日变化特征,夜雨多且雨量集中。伊宁的降水主要以短时性降水（1～4h）为主,多发生在前半夜至后半夜,1h降水频次最多的是量级≤1mm的降水,但1.1～3mm量级的降水贡献率最高。     

Variability of the TRMM-PR total and convective and stratiform rain fractions over the Indian region during the summer monsoon

Level 3 (3A25) TRMM Precipitation Radar (PR) data are used for 13 years period (1998–2010) to prepare climatology of TRMM PR derived near surface rain (Total rain) and rain fractions for the 4-months duration of Indian Summer Monsoon season (June–September) as well as for individual months. It is found that the total rain is contributed mostly (99 %) by two rain fractions i.e. stratiform and convective rain fractions for the season as well as on the monthly basis. It is also found that total rain estimates by PR are about 65 % of the gauge measured rain over continental India as well as on sub-regional basis. Inter-annual variability of TRMM-PR rain estimates for India mainland and its sub-regions as well as over the neighboring oceanic regions, in terms of coefficient of variability (CV) is discussed. The heaviest rain region over north Bay of Bengal (BoB) is found to have the lowest CV. Another sub-region of low CV lies over the eastern equatorial Indian ocean (EEIO). The CVs of total rain as well as its two major constituents are found to be higher on monthly basis compared to seasonal basis. Existence of a well known dipole between the EEIO and the north BoB is well recognized in PR data also. Significant variation in PR rainfall is found over continental India between excess and deficit monsoon seasons as well as between excess and deficit rainfall months of July and August. Examination of rainfall fractions between the BoB and Central India on year to year basis shows that compensation in rainfall fractions exists on monthly scale on both the regions. Also on the seasonal and monthly scales, compensation is observed in extreme monsoon seasons between the two regions. However, much less compensation is observed between the north BoB and EEIO belts in extreme rain months. This leads to speculation that the deficit and excess seasons over India may result from slight shift of the rainfall from Central India to the neighboring oceanic regions of north BoB. Contribution of stratiform and convective rain fractions have been also examined and the two fractions are found to contribute almost equally to the total rain. Results are further discussed in terms of the possible impact of the two rain fractions on circulation based on possible difference is vertical profiles of latent heat of two types of rain. Substantial differences in the lower and upper tropospheric circulation regimes are noticed in both deficit and excess monsoon months/seasons, emphasizing the interaction between rainfall (latent heat) and circulation.     

基于GPM卫星的广东汛期降水日变化特征与评估

新一代全球降水观测计划GPM作为TRMM卫星的继承者,在物理探测和降水反演算法上具有明显进步。以广东省雨量自动站为基准,对2014—2018年间GPM的格点降水估测产品IMERG（V5B）的日变化特征和估测误差进行分析。结果表明,IMERG能清晰反映广东前、后汛期的降水双峰型特征,但对下午降水峰值明显高估,峰值出现时间滞后;而对于沿海早晨峰值降水则明显低估,对于降水极值,低估更加显著。IMERG对两个峰值的估测误差受不同因素影响,下午峰值降水的相对偏差与地形密切相关,珠江三角洲平原为稳定高估区,地形高度越高,低估幅度越大;而早晨峰值降水极值负偏差与地形高度、降水量的相关性均较小。对出现显著负偏差的早晨沿海降水样本日进行925 hPa风场合成,可知IMERG明显低估时,对应区域上游较强的超低空西南气流与风速夜间增长。IMERG对这一季风活动背景降水的低估构成了其估测早晨降水误差的主要来源。