Analysis Of Drought Characteristics In The Southern Slope Of Qilian Mountains In The Recent 60 Years

The southern slope of Qilian Mountains is an important virgin forest distribution area and water source conservation area of Qinghai Province,and its ecological environment have the direct bearing on the water resource safety of Qinghai Province and Gansu Province.The distribution of precipitation is uneven in the southern slope of Qilian Mountains,and the precipitation is mainly concentrate in the summer.There is long duration of sunshine and strong evaporation where is easy to happen drought.It is of great theoretical and practical significance to the ecological security and water resources security in the southern slope of Qilian Mountains that understand the drought characteristics in the southern slope of Qilian Mountains.In this paper,the observed meteorological data of 4 meteorological stations from 1960 to 2015 in the southern slope of Qilian Mountains and the MODIS from 2001 to 2015 were collected,and the precipitation anomaly percentage(Pa),Z index and vegetation state index(VCI)was used.Based on the Pa,Z and VCI this paper analysis the drought characteristics in the southern slope of Qilian Mountains,which reveals the temporal,spatial and periodic characteristics of drought in the southern slope of Qilian Mountains in the past 60 years,provides the theoretical reference to protect ecological environment and water resources security in the southern slope of Qilian Mountain..The main research results were listed as follows:(1)Precipitation anomaly percentage reflects that January and December is easy to happen excessive drought while Z index reflects that the probability of light drought was the largest in January and December.Drought type of the four seasons mainly is light drought and moderate drought.Precipitation anomaly percentage reflects that high and excessive drought often occurs in the autumn and winter,Z index reflects the autumn and winter is prone to light drought.The drought level in the study area gradually decrease and the drought is prone to light drought in the recent 60 years.(2)The first major cycles of drought changes based on the precipitation anomaly percentage are about 13 years,16 years,12 years and 6 years at Tuole Station,Yeniugou Station,Qilian Station,and Menyuan Station respectively.The Yeniugou station and Menyuan station have obvious dry-wet changes on the 15-20 year time scale,the Tuole station and Qilian station have obvious dry-wet alternating process on the 10-15 year time scale.(3)The drought conditions of winter is more serious and high drought occurs in the large areas in the study area.In the summer,most areas without drought or light drought occurs in the study area,and high drought and moderate drought occurs in a small part of the study area.