| Using 0～30 cm soil moisture data per ten days during March to October from 1981 to 2002 in fixed locations of 17 meteorological stations,the temporal and spatial variations of shallow soil moisture in the east of Northwest China in recent 22 years were analyzed.The results show that soil moisture reduced from southwest to northwest.It had an obvious down tendency from 1981 to 2002,and it reached its peak in the first half of the 1980s.Soil moisture variable cycle is mostly 5 to 6 years.The period from 1986 to 1988 was a more consistent time of drought.Among spring,summer and autumn,the soil moisture in spring was the smallest and it was the largest in the autumn.In the past 22 years,soil moisture was reduced significantly in spring and autumn,especially in central Gansu. |