关键词: 宁夏, 降水, 集中度, 集中期

Abstract: Actually, most studies on the characteristics of spatiotemporal distributions of precipitation and its change trend are based on the annual or monthly average data in China. But these questions can not be made prominent about the change of maximum or minimum precipitation in a specific period. And these study subjects on the regional flood or drought are very important. So in this paper, based on the data of pentad precipitation from 1961 to 2010 including the main stations in Ningxia, the characteristics of spatiotemporal distributions of precipitation-concentration degree and precipitation-concentration period are studied. Using standard deviation, trend, correlation, synthesis and other statistical analysis methods, spatiotemporal distributions of PCD, PCP and their change trends are studied. Meanwhile, the effect of Arctic Oscillation and South China Sea monsoon in precipitation-concentration period are discussed. The study in this paper is expected to reveal the law of the precipitation change, to provide the basis on the Ningxia drought and flood forecasting. The result shows that the spatial distribution of PCP and PCD in Ningxia are obvious, PCP in central and northern areas of Ningxia is 1 pentad earlier than that in south mountain part of Ningxia. PCD was reduced from north to south. The temporal variability of yearly maximum precipitation in the north of Ningxia is bigger, and extreme precipitation in the north of Ningxia appears more likely than in the center and south of Ningxia. PCD and PCP in Ningxia displayed a weak decreasing trend from 1961 to 2010. But PCD was increased significantly and PCP was delayed significantly in recent 20 years. There is a good positive relationship between the PCD and PCP. The later PCP appears, more concentrative PCD is. There are good positive relationships between PCD and annual precipitation, flood season precipitation, daily maximum precipitation, and the center regions of positive relationships locate in Huinong，Taole, Zhongwei, Yanchi, Mahuangshan and the most region of south Ningxia. The more concentrative the precipitation is, the larger the annual precipitation, flood season precipitation, daily maximum precipitation are in those regions. It will lead to the floods possibility more likely. The precipitation is more concentrative in more precipitation years of flood season over parts of Ningxia. Large precipitation appears earlier in the north, later in the south of Ningxia. The impact of Arctic Oscillation in high latitudes and South China Sea monsoon in low latitudes against Ningxia precipitation-concentration is distinguished. Annual precipitation around Ningxia is concentrated in the years that Arctic Oscillation is weakness or South China Sea monsoon onset earlier, and vice versa. This paper[JP8]’s[JP] innovative points are as follows：PCD and PCP had a decreasing tendency nearly 50 years in Ningxia, but a present rising trend appears in the recent years; Higher PCD means more ability of drought, vice versa. In addition, there are some relationships between PCD and conditions of subtropical high pressure, activities of Arctic Oscillation (AO) and South China Sea summer monsoon.

Key words: Ningxia, precipitation, precipitation-concentration degree, precipitation-concentration period