Abstract:

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 occurs often 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.

Key words: Short-time heavy precipitation, Urbanization, Temporal and spatial distribution