关键词: 干旱半干旱地区, 年降水, 时空变异性, 插补

Abstract: Shapotou area is belonged to a steppe desert zone with a mean annual precipitation (MAP) of 191.1 mm (during 1955-2000). The stability of artificial-natural vegetation system in this area depends closely o n the annual precipitation character. Meanwhile, every precipitation event comes along with dust storm, which will contribute to the crust formation on the fixed sand dunes. For understanding the ecological function of this special phenomen on, the study on distribution, trends and variability of precipitation in Shapotou region is necessary. Time series of annual precipitation were examined for distribution and trends using Mann-Kendall rank statistic, and for variability using first order autocorrelation analysis. Results indicate that the annual precipitation in the 5-year moving value is above mean annual precipitation during the periods of 1967-1972 and 1977-1982, respectively. From 1983 to 2000, it is obviously that the annual precipitation is below MAP. The precipitation value in creased after it was decreased in two successive years in 1970s, but the trend is declined in general. In the case by calculating moving means, here illustrated the 5-year moving mean accentuates the oscillatory pattern suggested by the annual time series. The drought spells prolonged after the peak precipitation in 1 978, and it was terminated till 1985, which suggests the principle of prolonged dry spells usually precede or follow a precipitation season in desert region. In the transitional area of arid and semiarid region, Shapotou area is likely subjected to the arid zone.

Key words: arid and semiarid region, annual precipitation, spatial and temporal variability, interpolation