Characteristics of the diurnal variations of flood period precipitation in Anhui during the last 30 years

The characteristics of flood season daily precipitation were analyzed in the term of rainfall amount, frequency and intensity usingthe hourly data in Anhui during 1981-2010.The main results are as follows.(1) The daily rainfall amount and frequency have two diurnalpeaks, one in the early morning and the other in the late afternoon, while the rainfall intensity doesn't reflect an obvious peak.The peaks oflight and moderate rain days lie in afternoon, and there are two peaks in heavy rain days.However, the peak of torrential rain days lies inmorning.These differences are due to the different lasting rainfall events.(2)The spatial distributions of rainfall have large diurnal variationwith considerable regional features.As amount of daily rainfall increasing, the spatial distribution of peak time performs less consistent.(3)Inthe 30 years, the annual change of afternoon-peak in rain amount and intensity is almost the same, reflecting an increase between 1993 and2010.There are more stations of morning peak time in weak monsoon years than strong monsoon years.