Diurnal variation of precipitation over southeastern China: Spatial distribution and its seasonality

Using the satellite data, spatial patterns of precipitation diurnal cycles and their seasonality were examined with emphasis on southeastern China (SEC). Results show that spatial distributions of diurnal cycles over SEC have a robust large-scale seasonality in which the regional differences are evidently embedded. Rainfall diurnal variability is weak in spring but it becomes more pronounced from presummer. Both the mean rain rates and amplitudes of diurnal cycles experience remarkable amplification during presummer. The widespread and strong morning rainfall dominates the SEC area, especially inland valleys and plains, and offshore areas. The morning peak rainfall over western SEC is largely contributed by the increasing rain frequency and diurnally varying intense rain rates. Even over eastern SEC, morning rainfall still has a comparable magnitude to afternoon rainfall. In contrast, spatial distributions of diurnal cycles in midsummer are dependent primarily on topography. The morning (afternoon) rainfall is mainly located over valleys, basins, and oceans (plateaus and mountains). The afternoon peak rainfall becomes a notable feature over southern China. The signature of widespread morning rainfall decays during midsummer and remains apparent only in central eastern China, which is likely related to the north shift of summer rainband.