Abstract:

Based on the daily data of 103 meteorological stations in He'nan province from 1961 to 2019, the temporal statistical characteristics and spatial distribution characteristics of regional continuous precipitation were analyzed using moving average, wavelet analysis, and EOF decomposition. The regional circulation of continuous precipitation was objectively classified using the self-organizing maps (SOM) of neural network method. The results show that the process of continuous precipitation in autumn in He'nan province is mainly 7-9 days, followed by more than 10 days. In the 1960s and 1980s, the regional continuous precipitation in autumn occurs frequently in He'nan province, and in the 1990s, it occurs less frequently. The frequency in the 1970s and 2010s is the same as the average annual frequency in the recent 59 years. In the 2010s, it is stronger than that in other years, and the intensity is the weakest in the 1990s. The mean precipitation of continuous precipitation in autumn in the 1970s has a quasi-5-year period, and in the first half of the 2000s and 1980s it has a 2-3-year period. In recent 59 years, the regional mean precipitation of continuous precipitation in autumn in He'nan province is higher in the south of the Yellow River than that in the north of the Yellow River, and higher in the mountainous area than that in the plain area. The distribution of large precipitation values is basically the same as that of the mountainous area. On the spatial distribution pattern of regional mean precipitation of continuous precipitation in autumn in He'nan province, the most important characteristic is the consistent variation pattern of the whole province, followed by the inverse pattern of the north and south. The SOM method can not only distinguish the difference of circulation shape, but also distinguish the occurrence time of circulation pattern and the periodic evolution characteristics of circulation during continuous rainy and cloudy periods. According to the SOM classification, there are 8 types of regional circulation types with continuous precipitation, which can be summarized as blocking, low trough and direct circulations in synoptic sense. Most of the regional continuous precipitation processes in He'nan province are the combination of two or three circulation types, and there is a conversion relationship among different circulation types.

Key words: Regional continuous precipitation, SOM (self organizing maps), Circulation types