Abstract:
The short-duration heavy rain (hereafter SDHR) is one type of severe connective weather, and can directly or indirectly lead to large property and life losses.Based on the qualified hourly rain-gauge data from the 876 stations during April-September of 1991-2009 provided by the National Meteorological Information Center of China, the spatiotemporal distribution of SDHR over China during the warm season(April-September) is presented,and the comparison between SDHR and the MCS diurnal variations is focused on.It is found that the frequency spatial distributions of the SDHR denoted by hourly rainfall ≥10 mm,20 mm, 30 mm and 40 mm are very similar to that of heavy rainfall (daily rainfall ≥50 mm) over China (excluding Taiwan).However, the frequencies of the SDHR denoted by hourly rainfall ≥50 mm are much lower than those ≥20 mm/h, and,therefore,their spatial distributions are also much different.(hhe most active SDHR region is South China, and the second most active regions are southern Yunnan Province,Sichuan Basin,southern Uuizhou Province,Jiangxi Province,the lower rcaches of the Yangtze River, and so on.The heaviest hourly rainfall over China (excluding Taiwan) is more than 180 mm (over Hainan Island),and there are lots of SDHR events with hourly rainfall ≥50 mm over the inactive SDHR regions, such as the western Xinjiang Uygur Autonomous Region,the middle and eastern Inner Mongolia Autonomous Region.(hhe monthly variations of SDHR show that the most active SDHR month is July, and August the second most active.The pentad variations of SDHR reveal that the evolvement of SDHR has a characteristic of intermittence, and the most active SDHR pentad is the fourth pentad of July.The SDHR frequencies enhance slowly and weaken rapidly with the advance and withdraw of the summer monsoon over East Asia as shown in the monthly and pentad varitaions of SDHR over China.Over the entire China, the most active diurnal peak is 16:00-17:00 BT,the second and third active peaks 01:00-02:00 BT and 07:00-08:00 BT,respectively, and the most inactive period 10:00-13:00 BT.The diurnal variations of SDHR show that the active periods and propagation of SDHR and MCSs are different over the different regions of different underlying surface,with a single peak,two peaks,multiplc peaks and continued active type,which are not only associated with the largerscale atmospheric circulation,but also closely related to the terrain and land-sea distributions, for example,over South China, Guizhou Province,and Sichuan Province.