Spatial and temporal patterns of precipitation variability over mainland China:I: Climatology

Climatological characteristics of precipitation in mainland China are analysed by using an updated daily precipitation dataset from 2 300 stations for period 1956—2013. The new findings are as follows: ① The largest precipitation amount, days and intensity of rainstorms concentrate in the coastal zone of southern China, while the largest precipitation amount and days of light rain are mainly seen in inland mountains and hills south of the Yangtze River; in the eastern summer monsoon region, the highly intensive rain generally occurs in the low-laying plains and coastal zones, and the light rain mostly in the mountains and hills. ② Precipitation of all the seasons decreases from southeast to northwest; precipitation of autumn is much less than that of spring in southern China, but the autumn precipitation is more abundant in the Qinling Mountains, the Daba Mountains and the Sichuan Basin, and along the narrow coastal zone; the largest winter precipitation occurs in the hills region of south-eastern China. ③ Double to triple peaks of precipitation in a year appear in the Pear River basin, the south-eastern rivers and the mid-to lower Yangtze River basin, with the main peak in mid-to late June and secondary one in late August for the south-eastern rivers, for example, and main peak in June and secondary one in mid-August for the Pear River basin; all the northern rivers witness a single peak in late July. ④ The southern large rivers enter into rainy season gradually from late February to mid-to late June, and the northern large rivers enter into rainy season almost simultaneously in late June and early July; the close dates of rainy season are much concentrated across the eastern China, with the beginning time lasting for more than 120 d from the south to the north, and the closing time from the north to the south only lasting for less than 45 d. ⑤ The beginning and closing dates of potential flood season occur in the early May and the early September in the Pear River basin, the early May and the early July and then the late August and the beginning of September for second time in the south-eastern large river basins, the mid-to late June and the mid-July in the Yangtze River basin, the mid-July and the late August in the south-western large river basins, and the early July and the beginning of August in the Huaihe River basin; a very short potential flood season appears between the end of July and the beginning August in the Liaohe River basin, and no such a period can be found for the other northern large rivers. ⑥ The largest variability coefficients of annual and seasonal precipitation are found in the southwestern Tibetan Plateau, the Talimu Basin, the Alashan Plateau, northern part of the North China Plain and the Fenhe River basin of eastern Loess Plateau; the vast region south of the Yangtze River witnesses smaller inter-annual variability; the Haihe River basin registers the largest basin-averaged variability coefficients of annual precipitation in all of the ten large river basins of mainland China.