Evolution characteristics of the interannual and intra-annual precipitation in China from 1956 to 2016

To analyze the spatio-temporal distribution pattern of precipitation in China, the trend and mutation characteristics of the annual precipitation, as well as the temporal and spatial evolution of the intra-annual distribution, are summarized and analyzed using multiple methods based on the fused monthly precipitation monitoring data of the water conservancy department and the meteorological department of 4 177 stations from 1956 to 2016. These methods include the Mann-Kendall test, PETTITT test, and vector algorithm for intra-annual distribution, which explores the distribution pattern of several indices, including the precipitation-concentration degree, precipitation-concentration period, and the proportion indices of the maximum accumulated precipitation in four months to one year. The following conclusions are drawn : ① The temporal and spatial distribution of precipitation across China is not uniform. In general, the annual precipitation decreases, and the concentration of annual precipitation distribution increases from southeast to northwest; the changing trend of the annual precipitation at the stations shows a strong zonality with three bands of "increase-decrease-increase" from the southeast to the northwest; the bands showing a significant increase are located in the Southeast and Western China, and the bands showing a significant decrease are located in the central region, stretching from the northeast to the southwest to the border; and abrupt changes are often accompanied with the trend changes of the annual precipitation, of which most sites occur in the 1980s. ② Along the 200 and 400 mm annual precipitation contours, one band shows "flood season precipitation reduction" with strong temporal variation in North China. On the monthly scale, the proportion of precipitation in the flood season of the station decreases, and it increases in the non-flood season, while the opposite is true on the daily scale. The amplitude of accumulated precipitation for 3—7 consecutive days increases, suggesting that the extreme degree of precipitation events is increasing. ③ The changes in the precipitation series and the changes in the runoff series are well synchronized. The annual precipitation in Northwest and Southeast China shows an increasing trend, and the statistical discharge of the typical hydrological stations increases synchronously. However, the stations at which the annual precipitation decreases significantly and where the proportion indices of the maximum accumulated precipitation in four months to one year declines more than 10%, are concentrated in the non-humid areas of Northern China, such as the Liaohe River basin, Haihe River basin, and Yellow River basin. In these regions, the statistical discharge of the hydrological stations has decreased significantly.