2008—2012年南京短时强降水特征分析

Characteristics of short-time heavy precipitation from 2008 to 2012 in Nanjing

利用2008—2012年南京自动气象站逐时降水量的观测资料,分析南京短时强降水的发生规律,包括短时强降水的年变化、月变化、日变化和空间分布等特征。结果表明:2008—2012年南京雨强大于50 mm·h-1的致灾性短时强降水过程的发生次数呈显著增长的趋势;短时强降水天气主要出现在6—9月,其中7—8月出现日数最多,雨强最大。春雨期短时强降水最易发生在凌晨,梅雨期短时强降水最易发生在上午和傍晚,台汛期短时强降水最易发生在上午;下半夜—凌晨短时强降水出现次数较少,傍晚前后是短时强降水多发时段。短时强降水天气的空间分布具有明显的城郊差异,城市化效应不能引起城区的局地降雨,但在大尺度天气系统过境时,会使城区的对流活动较郊区更活跃,且城市下风向地区的降水也因此增强。

Based on hourly observed data from automatic weather stations in Nanjing from 2008 to 2012 annual,monthly and daily variation of short-time heavy precipitation and their spatial distribution were analyzed.The results indicate that the number of short-time heavy precipitation more than 50 mm·h^（-1） is in a significantly increasing trend from 2008 to 2012.Short-time heavy precipitation mainly occurs during June to September especially during July and August with the highest days and strongest intensity.For spring rain period,short-time heavy precipitation often occurs in the early morning;for Meiyu period it is often in the morning and early evening;for typhoon and flood period,it is also in the morning.In general,short-time heavy precipitation seldom occurs during midnight to early morning,while it often occurs about early evening.The spatial distribution characteristics of short-time heavy rain have obvious differences between urban and rural areas.The effect of urbanization does not lead to local heavy rain in the urban area,while it only makes the convection more active in the urban area than in the rural area under large scale weather system.Also precipitation in the lower reaches of urban area enhances because of the above reason.