中国暖季短时强降水分布和日变化特征及其与中尺度对流系统日变化关系分析

Analysis of the climatological distribution and diurnal variations of the short-duration heavy rain and its relation with diurnal variations of the MCSs over China during the warm season

  • 摘要: 短时强降水是强对流天气的一类.基于中国国家气象信息中心质量控制后的1991-2009年876个基本基准气象站整点逐时降水资料,通过不同时段的发生时次频率分析,给出了中国暖季(4-9月)不小于10、20、30、40、50 mm/h短时强降水的时空分布特征,并重点同利用静止气象卫星红外相当黑体亮度温度(TBB)资料获得的中尺度对流系统(MCS)日变化特征进行了对比分析.结果表明,中国短时强降水时次频率地理分布同暴雨(≥50mm/d)分布都非常相似,但50mm/h以上的短时强降水时次频率非常低,地理分布差异显着.短时强降水发生频率最高的区域为华南,其次为云南南部、四川盆地、贵州南部、江西和长江下游等地.最大降水强度可超过180mm/h(海南);在短时强降水发生频率很低的区域,也有超过50mm/h的强降水.从月际变化来看,7月最为活跃,其次为8月.逐候变化显示,短时强降水具有显着的间歇性发展特征(跳跃性分布的特征),但总体上呈现缓慢增强、迅速减弱的特点;以7月第4候最为活跃.中国总体平均的短时强降水的频率和最大强度的日变化有3个峰值,主峰在午后(16-17时,北京时),次峰在午夜后(01-02时)和早晨(07-08时);中午前后(10-13时)最不活跃.中国短时强降水和中尺度对流系统的日变化特征基本一致,但午夜后时段二者存在较大差异.不同区域的短时强降水和中尺度对流系统日变化具有不同的活跃时段和传播特征,具有单峰型、双峰型、多峰型和持续活跃型等日变化类型,这不仅与较大尺度的天气系统环流相关,且与地势、海陆等地理分布密切相关.

     

    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.

     

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