Analysis of characteristics of precipitation variation and mutation in Northern Shanxi

Based on the monthly precipitation data from 1960—2008 of 18 observation stations of Northern Shanxi,the spatial-temporal variation characteristics of precipitation are analyzed.The main results are as follows: The annual precipitation and the precipitation in summer and autumn is holistically in an increase trend,while the precipitation in spring and winter is holistically in a decrease trend.From the variations of spatial distribution,the annual and the seasonal precipitation increases gradually from the north to the south.The linear trend coefficients of annual precipitation are negative in most stations,but positive for the whole study area in spring,only positive in Fanshi in summer,negative in the southwestern region and positive in the northeastern region in autumn,with an equipotent probability of positive and negative in winter.The jumps are examined with methods including Mann-Kendall test,moving t-test and cumulative anomaly.The results show that an obvious abrupt change point in 1979 can be detected.From that time on,the annual precipitation begins to decline evidently.The abrupt change time in spring is near 1964 and 1991,while it is 1996 in summer.