The characteristics of flood season daily precipitation were analyzed in the term of rainfall amount, frequency and intensity using the hourly data in Anhui during 1981-2010. The main results are as follows. (1) The daily rainfall amount and frequency have two diurnal peaks, one in the early morning and the other in the late afternoon,while the rainfall intensity doesn't reflect an obvious peak. The peaks of light and moderate rain days lie in afternoon, and there are two peaks in heavy rain days. However, the peak of torrential rain days lies in morning. These differences are due to the different lasting rainfall events. (2)The spatial distributions of rainfall have large diurnal variation with considerable regional features. As amount of daily rainfall increasing,the spatial distribution of peak time performs less consistent. (3)In the 30 years, the annual change of afternoon-peak in rain amount and intensity is almost the same, reflecting an increase between 1993 and 2010. There are more stations of morning peak time in weak monsoon years than strong monsoon years.%采用1981—2010年安徽省逐时降水资料,从降水量、降水频次和降水强度三个方面对不同量级降水日变化进行分析,研究表明:(1)降水量和降水频次呈双峰结构,降水强度则无明显峰值.小雨和中雨降水量峰值时间主要在下午,大雨呈现出上下午双峰结构,暴雨的峰值则出现于上午.经分析,这是由于不同日降水量级下持续性降水事件的构成不同所导致;(2)在空间分布上,各量级降水日变化有明显区域性特征.总体来看量级较小的降水峰值出现时间的空间分布较为一致,量级越大则一致性越差;(3)近30 a出现在下午的降水量峰值和降水强度峰值的年际变化较为一致,均在1993—2001年间有所加强.且在东亚夏季风较强的年份,安徽省降水峰值时间主要集中在午后;而在弱季风年,峰值时间出现于早晨的站点偏多.
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