Characteristics of temporal and spatial distribution of regional rainstorm processes to the east of 95°E in China during 1981-2015

The events of the regional rainstorm processes (RRP) to the east of 95°E in China over 1981-2015 are constructed based on intensive daily observations of precipitation in China and NCEP/NCAR reanalysis data by means of subjective and objective analyses. Temporal and spatial characteristic distribution of RRP in China are further investigated using the methods of wavelet power spectrum, nine-point binomial smoothing and Ward cluster analysis. The main conclusions are as follows. (1) The annual average number of RRP to the east of 95°E in China is nearly 30. RRP in the Yangtze-Huaihe River valley occur most frequently among the six subareas with an annual average number of about 19, followed by that in South China and eastern part of Southwest China with annual average numbers of 10.5 and 5.8 times respectively. Annual average number of RRP is only about 1-3 in other subareas. (2) The inter-annual and inter-decadal variations of the annual number of RRP exhibit distinct fluctuation characteristics. The inter-annual and inter-decadal fluctuating variation in the Yangtze-Huaihe River valley is the most consistent with that to the east of 95°E in China. Moreover, the fluctuating variations have a significant positive correlation between South China and eastern part of Southwest China, and also between Northeast China and North China. The annual number of RRP over the east of 95°E in China and its subareas demonstrates a periodic variation of 2-4 a, and also a periodic variation of 6-10 a in the Yangtze-Huaihe River valley, South China and eastern part of Northwest China, while a 13-17 a oscillation can be found in North China. (3) On the whole, the occurrence frequency of RRP to the east of 95°E in China is the most in summer (especially in July), the least in winter, and higher in spring than in autumn. The months when RRP occur most frequently are June and July in the Yangtze-Huaihe River valley and eastern part of Southwest China, and May and June in South China. RRP mainly appear in July and August in other subareas. (4) The distribution pattern of RRP to the east of 95°E in China are divided into 7 types. The heavy precipitation areas for pattern Ⅰ-Ⅳ migrate northward step by step from South China and southern part of Yangtze River valley to Huanghuai Basin and eastern part of Sichuan Basin. The heavy precipitation areas of pattern Ⅴ-Ⅶ all are located at the coastal region of Southeast China, moreover precipitation of pattern Ⅴ are concentrated from the eastern part of South China to Huaihe River, and precipitation of pattern Ⅵ are located from the northern part of Huanghuai Basin to central-southern part of Northeast China, precipitation of pattern Ⅶ are concentrated over the western part of Huanghuai Basin and central-southern part of North China.