Analysis of hourly precipitation characteristics during the warm season over different districts of Northeast China

Northeast China (NEC) has frequent flood disasters and significant spatial distribution differences in precipitation. In order to reveal precise precipitation characteristics of different regions in NEC, based on the hourly precipitation dataset of 1 611 national automatic weather stations over NEC in warm seasons (from May to September) from 2009 to 2021, the article first analyses spatial distribution of precipitation amount, frequency, intensity and duration, and studies characteristics of intensity structure in different districts via E-index fitting method and the relationship between precipitation characteristics and altitude in representative districts. Then, the diurnal characteristics of precipitation and precipitation events with different durations precipitation in four typical districts in NEC are analyzed based on the peak time and amplitude of precipitation characteristics. Finally, the symmetry of precipitation in NEC is analyzed, and the asymmetry and temporal evolution characteristics of precipitation characteristics in two typical districts are synthesized and analyzed based on the peak time of heavy precipitation events. The results are as follows:(1) The precipitation and frequency in NEC show a distribution of more in the east and less in the west, while the hourly precipitation intensity is stronger in plains than in mountains, with both precipitation amount and frequency increasing as the altitude rises. Precipitation over Greater Khingan Mountain is relatively weak, with both precipitation amount and frequency decreasing as the altitude rises. (2) Both the diurnal peaks of precipitation amount and precipitation intensity occur in the afternoon over most of NEC, which is dominated by short-duration strong precipitation, while the diurnal peak of precipitation frequency occurs in the midnight and early morning over NEC plains and Changbai Mountain, which is mainly contributed by long-duration weak precipitation in Changbai Mountain area. (3) Based on the composite peak time of the precipitation process, certain asymmetry is found before and after the peak of strong precipitation events in the Northeast region, where precipitation can reach the peak quickly and maintain for a long time after reaching the peak. The asymmetry of precipitation evolution over Changbai Mountain is weaker than that of other regions.