DIURNAL CYCLES OF CONVECTIVE AND STRATIFORM PRECIPITATION OVER NORTH CHINA DURING SUMMER

The diurnal cycles of precipitation over north China during summer in four strong rainfall years are examined using two-dimensional cloud-resolving modeling data. The diurnal signals are analyzed in terms of precipitation budget, fractional rainfall coverage and rain intensity over convective and stratiform rainfall area. The analysis of precipitation budget shows that the diurnal cycles of convective and stratiform precipitation mainly correspond respectively to those of water vapor convergence and transport of hydrometeor from convective rainfall area to stratiform rainfall area in 1964, 1994 and 1995, whereas they mainly correspond to those of water vapor convergence in 2013. The diurnal cycles of convective and stratiform precipitation are mainly associated with those of rain intensity in 1964, 1994 and 1995. In 2013, the diurnal cycle of stratiform precipitation is mainly related to that of fractional rainfall coverage over stratiform rainfall area. The multiple peaks of convective precipitation mainly correspond to the rain intensity maxima associated with strong water vapor convergence.     

亚洲季风区积云降水和层云降水时空分布特征及其可能成因分析

本文利用最近12年的TRMM (Tropical Rainfall Measuring Mission)卫星资料,分析了亚洲季风区积云降水和层云降水的时空分布特征.结果表明:从多年平均角度看,亚洲季风区积云降水和层云降水空间分布主要呈现出随纬度变化的特征:25°N以北的副热带季风区以层云降水方式为主,其所占比例在50％...     

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     

Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall

Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall are examined with the equilibrium simulation data from three experiments conducted with a two-dimensional cloud resolving model with imposed temporally and zonally invariant winds and sea surface temperature and zero mean vertical velocity. The experiment without ice radiative effects is compared with the control experiment with ice microphysics (both the ice radiative and microphysical effects) to study effects of ice radiative effects on diurnal rainfall variations whereas it is compared with the experiment without ice microphysics to examine ice microphysical effects on the diurnal rainfall variations. The ice radiative processes mainly affect diurnal cycle of convective rainfall whereas the ice microphysical processes have important impacts on the diurnal cycles of both convective and stratiform rainfall. Turning off the ice radiative effects generally enhances convective rainfall during the morning and evening and suppresses convective rainfall in the afternoon whereas turning off the ice microphysical effects generally suppresses convective and stratiform rainfall during the morning and enhances convective and stratiform rainfall in the afternoon and evening. The ice radiative and microphysical effects on the diurnal cycle of surface rainfall are mainly associated with that of vapor condensation and deposition, which is controlled by air temperature through saturation specific humidity. The ice effects on the diurnal cycle of local temperature tendency are largely explained by that of latent heating since the diurnal cycle of radiation is insensitive to the ice effects.     

两次华北冷涡降水成因及预报偏差对比分析

利用多种常规及非常规观测资料、美国国家环境预报中心全球模式业务系统分析资料(NCEP/FNL)以及三家全球确定性模式产品对2017年两次华北冷涡降水过程成因及模式预报偏差进行了对比分析。结果表明;个例1(6月22日)降水回波为层-积混合型,对流发展高度低,小时雨强小,先后经历了持续的稳定降水和弱对流降水两个阶段;个例2(7月6日)降水以积云状对流回波为主,对流发展高度高,短历时强降水特点明显。二者对应的环境场差异较大,前者冷涡处在成熟期,副热带高压位置偏南,前期暖区对流冷池降温明显,对流能量及水汽条件一般;后者冷涡为发展期,副热带高压位置偏北,中低纬相互作用明显,水汽与能量充沛。两次过程北京均出现了暴雨及以上量级降水,对应的中尺度对流系统(MCS)特征、对流触发机制以及对流不稳定能量重建过程存在明显差异。前者为层状云中发展的γ中尺度MCS,边界层偏东风增强为MCS提供了触发机制,中低层偏东风暖湿输送以及对流层高层干冷平流有利于对流不稳定能量重建;后者为组织化的β中尺度MCS,列车效应明显,偏南低空急流及其气旋式切变配合地形为MCS发展提供了抬升条件,对流不稳定能量建立与中低层偏南低空急流强暖湿输送有关。各家数值模式对不同类型冷涡降水的预报偏差特征一致,即对冷涡成熟期的降水,因对动力条件预报过强导致空报降水;而对冷涡发展期的降水,由于对槽前暖区辐合及其对流性降水预报不足导致强降水出现漏报。     

Diurnal phase of late-night against late-afternoon of stratiform and convective precipitation in summer southern contiguous China

Using the tropical rainfall measuring mission (TRMM) Precipitation Radar (PR) observations combined with the surface rain gauge data during 1998–2006, the robust diurnal features of summer stratiform and convective precipitation over the southern contiguous China are revealed by exploring the diurnal variations of rain rate and precipitation profile. The precipitation over the southern contiguous China exhibits two distinguishing diurnal phases: late-night (2200–0600 LST) and late-afternoon (1400–2200 LST), dependent on the location, precipitation type and duration time. Generally, the maximum rain rate and the highest profile of stratiform precipitation occur in the late-afternoon (late-night) over the southeastern (southwestern) China, while most of the stratiform short-duration rain rate tends to present late-afternoon peaks over the southern China. For convective precipitation, the maximum rain rate and the highest profile occur in the late-afternoon over most of the southern contiguous China, while the convective long-duration rain rate exhibits late-night peaks over the southwestern China. Without regional dependence, the convective precipitation exhibits much larger amplitude of diurnal variations in both near surface rain rate and vertical extension compared with stratiform precipitation and the convective rain top rises most rapidly between noon and afternoon. However, there are two distinctive sub-regions. The diurnal phases of precipitation there are very weakly dependent on precipitation type and duration time. Over the eastern periphery of the Tibetan Plateau, the maximum rain rate and the highest profile of either convective or stratiform precipitation occur in the late-night. Over the southeastern coastal regions, both the near surface rain rate and rain top of convective and stratiform precipitation peak in the late-afternoon.     

On the Diurnal Cycle of Heavy Rainfall over the Sichuan Basin during 10–18 August 2020※

A sustained heavy rainfall event occurred over the Sichuan basin in southwest China during 10–18 August 2020, showing pronounced diurnal rainfall variations with nighttime peak and afternoon minimum values, except on the first day. Results show that the westward extension of the anomalously strong western Pacific subtropical high was conducive to the maintenance of a southerly low-level jet (LLJ) in and to the southeast of the basin, which favored continuous water vapor transport and abnormally high precipitable water in the basin. The diurnal cycle of rainfall over the basin was closely related to the periodic oscillation of the LLJ in both wind speed and direction that was caused by the combination of inertial oscillation and terrain thermal forcing. The nocturnally enhanced rainfall was produced by moist convection mostly initiated during the evening hours over the southwest part of the basin where high convective available potential energy with moister near-surface moist air was present. The convective initiation took place as cold air from either previous precipitating clouds from the western Sichuan Plateau or a larger-scale northerly flow met a warm and humid current from the south. It was the slantwise lifting of the warm, moist airflow above the cold air, often facilitated by southwest vortices and quasi-geostrophic ascent, that released the convective instability and produced heavy rainfall.     

星载测雨雷达探测的夏季亚洲对流与层云降水雨顶高度气候特征

利用热带测雨卫星测雨雷达的10年探测结果,对夏季亚洲对流降水与层云降水雨顶高度分布、雨顶高度与地表降水强度的关系、雨顶高度日变化特征进行了研究。结果表明,青藏高原和中国东部平原的多数(70%以上)对流降水雨顶高度分布在8—12和5—10km,其他地区分布在5—9km;陆面对流降水雨顶平均高度高于洋面。洋面和陆面层云降水雨顶高度没有明显差异,多在5—8km。夏季亚洲浅对流降水比例少,而深厚对流主要出现在中国东部平原、西南、印度次大陆西部至伊朗高原东部地区,比例约40%。洋面和陆面的弱对流降水的雨顶平均高度在7—8km,弱层云降水相应的雨顶平均高度多小于7.5km;陆面约90%的强对流降水雨顶平均高度在9km以上,而强层云降水雨顶的平均高度通常不超过8.5km。夏季亚洲对流降水和层云降水的雨顶平均高度均随着地面平均降水率的增大而升高,两者遵从二次函数关系。对流降水及层云降水频次、强度和雨顶高度的日变化峰值分析表明,陆面这些参量的日变化强于洋面,并且三者的日变化基本同步。     

对流尺度数值预报中的云物理初始化方法改进及个例试验

通过在云初始化方案中增加由地表感热和潜热通量确定的对流尺度速度作为对流判据,同时增加层云云冰、云水计算方案,改进云分析方法,并基于第2代华东快速更新循环同化模式预报系统,针对2015年4月28日华东强对流个例,进行对比试验,分析了改进的云初始化方案对云分析结果和模式预报效果的影响。试验表明:在云分析中增加对流判据,使得平均40%左右的云分析格点判定为非对流格点,对流格点分布与正的感热通量分布相似,在陆地上有显著日变化。在对流和层云格点判定之后,增加层云云冰、云水计算方案分析层云格点,显著地减小了模式初始场的云冰、云水混合比,有效地减弱了模式积分初始阶段云冰、云水含量的剧烈调整,尤其是在陆地区域。采用改进的云初始化方案进行预报,可以减少模式前1 h和前6 h的降水强度;尤其在个例的循环试验中,强降水中心强度和面积的预报比原方案显著减弱。      

A Modeling Study of Surface Rainfall Processes Associated with a Torrential Rainfall Event over Hubei, China, during July 2007

The surface rainfall processes associated with the torrential rainfall event over Hubei,China,during July 2007 were investigated using a two-dimensional cloud-resolving model.The model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction(NCEP)/Global Data Assimilation System(GDAS) for 5 days.The time and model domain mean surface rain rate was used to identify the onset,mature,and decay periods of rainfall.During the onset period,the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface rainfall.The local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform rainfall.During the mature periods,the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform rainfall.Both convective and stratiform rainfalls made important contributions to the model domain mean surface rainfall.During the decay period,descending motion data input into the model prevailed,making stratiform rainfall dominant.Stratiform rainfall was mainly caused by the water vapor convergence over raining stratiform regions.     

TRMM测雨雷达对1998年东亚降水季节性特征的研究

利用热带测雨计划卫星上的测雨雷达得到的降水资料,对1998年东亚降水,特别是中国大陆东部、东海和南海的降水,进行了分析研究,并对比了热带降水研究结果。年统计结果表明,东亚地区层状云降水出现概率极高(比面积达83.7％),对流云降水的比面积仅占13.6％,然而两者对总降水量的贡献相当。结果还表明,暖对流云降水出现的比例和对总降水量的贡献很小。在季节尺度,对流云和层状云降水的比与两者的面积比成比例关系。除夏季外,测雨雷达降水量与GPCP降水量可比性好。研究结果还指出:在中纬度陆地和海洋上对流云和层状云的比降水量和比面积呈相反方向作季节性南北移动,这一活动与东亚季风变化一致;该地区降水的季节性变化还表现为降水垂直廓线的变化。除冬季外,南海地区降水垂直结构呈热带特征。CRAD分析表明,对流云降水的地面雨强变化大,尤其在陆地上,而层状云多表现为地面弱降水。     

A STUDY ON THE PRECIPITATION CHARACTERISTICS OVER THE SOUTH CHINA SEA BEFORE AND AFTER THE MONSOON ONSET

This paper presents a study on the temporal and spatial variations of the precipitation over the area of the South China Sea (SCS) during the monsoon onset period. The data used are from the Tropical Rainfall Measuring Mission (TRMM) observations between April and June over the nine years from 1998 to 2006. This study focuses on the central and northern part of South China Sea (110-120°E, 10-20°N). Based on the observations, the 27th pentad is selected as the occurrence time of the SCS monsoon onset. The conclusions are as follows. (1) After the monsoon onset, the specific area, defined as the ratio of the number of pixels with certain type of precipitation to the number of total pixels, extends significantly for both convective and stratiform rain, with the latter having a larger magnitude. The specific rainfall, defined as the ratio of the amount of certain type of precipitation to the total amount of precipitation, decreases for convective rain and increases for stratiform rain. (2) Results also show significant increase in heavy rain and decrease in light rain after the monsoon onset. (3) Changes are also observed in the rainfall horizontal distributions over the SCS before and after the monsoon onset, manifested by the relocation of precipitation minima for both convective and stratiform rain. (4) After the monsoon onset, the variability in characteristics of precipitation vertical structure increases significantly, leading to more latent heat release and consequently deeper convection. Meanwhile, the bright-band altitude of stratiform precipitation is also elevated.     

Statistical Characteristics of Raindrop Size Distribution in the Tibetan Plateau and Southern China

The characteristics of raindrop size distribution(DSD) over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu and Yangjiang, comprising a total of 9430 and 6366 1-min raindrop spectra, respectively. The raindrop spectra, characteristics of parameter variations with rainfall rate, and the relationships between reflectivity factor(Z) and rainfall rate(R) are analyzed, as well as their DSD changes with precipitation type and rainfall rate. The results show that the average raindrop spectra appear to be one-peak curves, the number concentration for larger drops increase significantly with rainfall rate, and its value over southern China is much higher, especially in convective rain. Standardized Gamma distributions better describe DSD for larger drops, especially for convective rain in southern China. All three Gamma parameters for stratiform precipitation over the Tibetan Plateau are much higher, while its shape parameter(μ) and mass-weighted mean diameter(D_m), for convective precipitation, are less. In terms of parameter variation with rainfall rate, the normalized intercept parameter(N_w) over the Tibetan Plateau for stratiform rain increases with rainfall rate, which is opposite to the situation in convective rain. The μover the Tibetan Plateau for stratiform and convective precipitation types decreases with an increase in rainfall rate, which is opposite to the case for D m variation. In Z–R relationships, like "Z = AR~b", the coefficient A over the Tibetan Plateau is smaller, while its b is higher, when the rain type transfers from stratiform to convective ones. Furthermore, with an increase in rainfall rate, parameters A and b over southern China increase gradually, while A over the Tibetan Plateau decreases substantially, which differs from the findings of previous studies. In terms of geographic location and climate over the Tibetan Plateau and southern China, the precipitation in the pre-flood seasons is dominated by strong convective rain, while weak convective rain occurs frequently in northern Tibet with lower humidity and higher altitude.     

利用星载测雨雷达探测结果对夏季中国南方对流和层云降水气候特征的分析

本文利用热带测雨卫星(TRMM)上搭载的测雨雷达(PR)十年的探测结果, 对夏季中国南方对流降水和层云降水的气候特征进行了分析。研究结果表明:夏季中国南方层云降水频次较对流降水频次高出两倍以上, 而对流降水强度至少是层云降水强度的4倍; 就整个中国南方而言, 这两种类型的降水对总降水量贡献相当。日变化分析表明夏季中国南方大部分地区的对流降水主要出现在午后, 层云降水出现时间并不集中, 但这两类降水的频次日变化均显示了明显的地域性特征; 对降水廓线日变化的分析结果表明, 对流降水和层云降水廓线的日变化主要表现在“雨顶”高度的日变化, 即对流降水云的厚度有明显的日变化变化特征, 不同地区的降水廓线存在明显的差异。降水率剖面分析结果显示了对流降水的“雨顶” 高度日变化较层云降水剧烈, 降水率的日变化则相反, 且层云降水率的地域性特征更强。     

Simulation of the annual and diurnal cycles of rainfall over South Africa by a regional climate model

The capability of a current state-of-the-art regional climate model for simulating the diurnal and annual cycles of rainfall over a complex subtropical region is documented here. Hourly rainfall is simulated over Southern Africa for 1998–2006 by the non-hydrostatic model weather research and forecasting (WRF), and compared to a network of 103 stations covering South Africa. We used five simulations, four of which consist of different parameterizations for atmospheric convection at a 0.5 × 0.5° resolution, performed to test the physic-dependency of the results. The fifth experiment uses explicit convection over tropical South Africa at a 1/30° resolution. WRF simulates realistic mean rainfall fields, albeit wet biases over tropical Africa. The model mean biases are strongly modulated by the convective scheme used for the simulations. The annual cycle of rainfall is well simulated over South Africa, mostly influenced by tropical summer rainfall except in the Western Cape region experiencing winter rainfall. The diurnal cycle shows a timing bias, with atmospheric convection occurring too early in the afternoon, and causing too abundant rainfall. This result, particularly true in summer over the northeastern part of the country, is weakly physic-dependent. Cloud-resolving simulations do not clearly reduce the diurnal cycle biases. In the end, the rainfall overestimations appear to be mostly imputable to the afternoon hours of the austral summer rainy season, i.e., the periods during which convective activity is intense over the region.     

Introduction to the Regional Coupled Model WRF4-LICOM: Performance and Model Intercomparison over the Western North Pacific

Regional coupled modeling is one of the frontiers of regional climate modeling, but intercomparison has not been well coordinated. In this study, a community regional climate model, WRF4, with a resolution of 15 km, was coupled with a high-resolution(0.1°) North Pacific Ocean model(LICOM_np). The performance of the regional coupled model,WRF4_LICOM, was compared to that of another regional coupled model, RegCM4_LICOM, which was a coupling of version 4 of the Regional Climate Model(RegCM4) with LICOM_np. The analysis focused on the 2005 western North Pacific summer monsoon rainfall. The results showed that the regional coupled models with either RegCM4 or WRF4 as their atmospheric model component simulated the broad features over the WNP reasonably well. Quantitative intercomparison of the regional coupled simulations exhibited different biases for different climate variables.RegCM4_LICOM exhibited smaller biases in its simulation of the averaged June–July–August SST and rainfall, while WRF4_LICOM better captured the tropical cyclone(TC) intensity, the percentage contributions of rainfall induced by TCs to the total rainfall, and the diurnal cycle of rainfall and stratiform percentages, especially over land areas. The different behaviors in rainfall simulated by the two models were partly ascribed to the behaviors in the simulated western North Pacific subtropical high(WNPSH). The stronger(weaker) WNPSH in WRF4_LICOM(RegCM4_LICOM) was driven by overestimated(underestimated) diabatic heating, which peaked at approximately 450 hPa over the region around the Philippines in association with different condensation–radiation processes. Coupling of WRF4 with LIOCM is a crucial step towards the development of the next generation of regional earth system models at the Chinese Academy of Sciences.     

Warm-Season Diurnal Variations of Total,Stratiform, Convective,and Extreme Hourly Precipitation over Central and Eastern China

Diurnal variations in amount, frequency and intensity of warm-season hourly precipitation(HP) at seven levels, which are defined as HP 0.1, 0.5, 1, 5, 10, 20 and 50 mm, are revealed based on no less than 30 years of hourly rain-gauge observations at national stations over central and eastern China(CEC). This study investigates the variations, relationships, differences and similarities of total, stratiform, convective and extreme HP over the entire CEC and various subregions. Results indicate that the variations in the amount and frequency of HP at the seven levels over the entire CEC all display a bimodal feature. For various regions, the variations of total HP mostly feature two peaks, while convective HP mainly occurs in the late afternoon and determines the diurnal variation of total HP intensity. On the basis of the primary peak time periods of HP frequency at all levels over different subregions, the variations can be classified into three main categories: late-afternoon primary peak, nocturnal primary peak, and time-shifting primary peak. However, the variations over some coastal regions like the Liaodong Peninsula, the Shandong Peninsula, and the coastal regions of Guangdong, distinctly differ from those over their corresponding larger regions. Overall, the normalized diurnal variation amplitude of amount and frequency increases with the increasing HP intensity; convective precipitation can be represented by HP 10 mm; and the intensity of HP 50 mm is slightly larger during the nighttime than during the daytime over the entire CEC. In northern China, diurnal variation in HP 5 mm can represent well that in convective precipitation.     

Surface rainfall and cloud budgets associated with mei-yu torrential rainfall over eastern China during June 2011

Surface rainfall and cloud budgets associated with three heavy rainfall events that occurred over eastern China during the mei-yu season in June 2011 were analyzed using 2D cumulus ensemble model simulation data.Model domain mean rainfall showed three peaks in response to three prescribed ascending motion maxima,primarily through the mean moisture convergence during the torrential rainfall period.Prescribed ascending motion throughout the troposphere produced strong convective rainfall during the first （9 June） and third （17-18 June） rainfall events,whereas strong prescribed ascending motion in the mid and upper troposphere and weak subsidence near the surface generated equally important stratiform and convective rainfall during the second rainfall event （14 June）.The analysis of surface rainfall budgets reveals that convective rainfall was associated with atmospheric drying during the first event and moisture convergence during the third event.Both stratiform and convective rainfall responded primarily to moisture convergence during the second event.An analysis of grid data shows that the first and third mean rainfall maxima had smaller horizontal scales of the precipitation system than the second.     

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。     

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.