江苏暖季短时强降水的时空不均匀特征分析

Temporal and spatial heterogeneity of warm-season short-time heavy rainfall in Jiangsu Province

摘要:

利用江苏近10 a（2005-2014年）暖季（5-9月）69站逐时降水资料，详细分析了短时强降水的空间分布、年际变化、季节内演变以及日变化特征。分析结果表明：短时强降水空间分布不均，整体上北部比南部活跃，最活跃区均位于沿淮西部，高强度短时强降水多发生在淮北东部，且空间分布集中。近10 a来江苏短时强降水整体呈减少趋势，主要表现为北部地区减少最为显著。短时强降水季节内分布不均匀，以7月最为活跃，高强度短时强降水在8月最为频繁；其逐候分布显示，梅期短时强降水骤增，于7月第2候达到峰值，盛夏期间高强度短时强降水增多，8月第3候达到峰值。江苏短时强降水的日变化整体呈双峰结构，主峰和次峰分别出现在傍晚17时（北京时间，下同）和清晨07时，高强度短时强降水多发于午后；短时强降水日变化存在季节内演变的阶段性特征和地域性差异，其中梅期和盛夏两个高发阶段均呈单峰结构，但梅期峰值出现在清晨，盛夏阶段峰值则出现在傍晚；由南向北，日变化特征由单峰向双峰、多峰演变，在淮河以南地区日峰值大多出现在午后至傍晚，而淮河以北地区多出现在夜间至清晨。

关键词:短时强降水;日变化;时空不均匀;暖季

Abstract:

Based on hourly precipitation observation data during the warm season(May to September) of 2005-2014 from 69 gauge stations in Jiangsu,the spatial and temporal distributions of short-time heavy rainfall(≥ 20 mm/h) have been analyzed,which showed obvious heterogeneity in space and time.The occurrence frequency of short-time heavy rainfall in northern Jiangsu area was higher than that in the southern region,and its most active region is located in the western area along Huaihe River.Meanwhile,extreme short-time rainfall events(≥ 50 mm/h) frequently occurred in the eastern Huaibei with concentrated rainfall distributions.The occurrence frequency of short-time heavy rainfall showed the decreasing trend in the past decade,especially in northern Jiangsu.In general,July was the most active month of short-time heavy rainfall,and the extreme short-time rainfall events occurred most frequently in August.The pentad short-time heavy rainfall evolved with the phase variations that the frequency of short-time heavy rainfall increased rapidly during Meiyu season with the peak in the second pentad of July,and then the frequency of extreme short-time rainfall events increased obviously during mid-summer and reached its peak in the third pentad of August.In average,the diurnal variations of short-time heavy rainfall showed a double-peak pattern,with the highest peak around 17:00 BST and the secondary peak around 07:00 BST,while extreme short-time heavy rainfall events tended to occur in the afternoon.The diurnal variations of short-time heavy rainfall also demonstrated obvious sub-seasonal variability and spatial differences.It had a single peak in early morning during Meiyu season and a single peak in the evening during mid-summer.From the south to the north of Jiangsu,the diurnal pattern evolved from a single peak to double and multiple peaks.The peak appeared mostly in the afternoon in the southern area of Huaihe River,while mainly appeared during the night to early morning in the northern area of Huaihe River.

Key words:short-time heavy rainfall;diurnal variation;temporal and spatial heterogeneity;warm-season