Characteristics of soil drought at Loess Plateau of China

By investigating the meteorological data of 51 stations during recent 40 years,the whole and regional distribution of soil drought variation at the Loess Plateau of China was studied.The results show that the main spatial-temporal variability of abnormal soil drought has the same trend in whole of the plateau that the soil drought has gradually aggravated in recent years.In soil drought calculation,1973 and 1989 was Petitt change points.The drought years were less than rainy ones before 1973 and more than rainy ones after 1989 in the region.The sensitivity area of soil-drought was in the center of the Loess Plateau.Range of drought change in peripheral area of the plateau was less than other areas.In wavelet analysis,soil drought has a remarkable 2-4 year period and a clear spatial evolution of 2 year sub-oscillation.The variation of soil drought spread from center to periphery of the plateau within 5 months.The soil drought varied slower in the edge part than that in the center of the plateau in the next 5 months.Spatiotemporal change and intensity of soil drought have regional difference,which mainly distributed at the 5 sub-regions of the Loess Plateau: the west part of the plateau,the middle Shanxi basin,the north-east part of the plateau,the central Shaanxi Plain and the upper reaches of the Weihe River.