Regional characteristics of diurnal peak phases of precipitation over contiguous China

Diurnal variations in amount, frequency, and intensity of warm season precipitation were studied and compared using the hourly rain-gauge data from the high-resolution national surface stations of China. It was found that there are three kind phases for the diurnal peak of precipitation: afternoon, early morning, and night. Overall, the frequency tends to peak in the early morning, while the intensity reaches the maximum in the afternoon. Taking the peak phases of both amount and frequency into account simultaneously, seven key regions were divided: two afternoon-peak regions (AN_N, AN_S), two night-peak regions (MN_N, MN_S), two early-morning-peak regions (EM_N, EM_S), and a region over the Tibetan Plateau (EVE_TP, with evening peaks). Precipitation amount and frequency at most stations within these key regions present coherent peak phases. In contrast, stations located out of the key regions tend to have opposite peak phases: the afternoon peak of precipitation amount versus the early morning peak of precipitation frequency. An important feature of the overall phase pattern is that the phase of the amount lags (leads) that of the intensity (frequency) in regions with afternoon, evening, or night peaks,which indicates the asymmetry of precipitation processes and the evolvement of convective clouds.