| The ecological environment in arid areas is extremely fragile,it severely restricts the construction of local ecological environment and economic development.As one of the important roles in the fields of agricultural production and life,hydrological dynamics research,and ecological environmental protection,soil moisture is a relative variable representing soil water content,and it is the key connection point of the coupling mechanism of atmospheric water,surface water and groundwater.Therefore,it has great significance to study the distribution of soil moisture and its influencing factors for the hydrothermal balance and ecological environmental protection in arid areas.Located in the middle of the southern margin of Qaidam Basin,Golmud river basin is a typical arid area.Based on MODIS data,this paper inverts the spatial and temporal variation of soil moisture in the Golmud River Basin from 2002 to 2016 and analyzes its influencing factors using the method of apparent thermal inertia(ATI).The result has great significance to the development and utilization of local water resources and the protection of ecological environment.The result indicated that:(1)Generally,ATI was increased from 2002 to 2016 and the trends was validated using Mann-Kendall test.It is showed that ATI had a mutation in 2008 and the increase trend was very obvious.(2)According to the interpretation of different land use,the mean value of ATI in the salt pond in the northernmost part of the study area was the highest(0.088),followed by natural vegetation(0.034)and cultivated land(0.033)which were distributed around the east side and west side of Golmud city.The distribution of ATI in rivers was less and sparse,and the mean value of ATI was slightly lower than that of plants.The mean value of ATI in bare desert soil in the north-central and southern regions was the lowest(0.028).(3)The reliability of the inversion results was verified by using 2 methods.The coefficient of determination of CLDAS soil moisture products and remote sensing inversion results is 0.853,the coefficient of determination of measured soil moisture content and remote sensing inversion results is 0.588,respectively,showing a high correlation.The results of soil moisture inversion by the method of Apparent Thermal Inertia are reliable.(4)Between 2002 and 2016,NDVI and ATI showed an overall increasing trend,the distribution of NDVI(excluding water)was generally consistent with the distribution of ATI,and the determination coefficient was up to 0.920.In arid and semi-arid regions,vegetation had a certain indicating effect on soil moisture.(5)Between 2002 and 2016,evaporation(ET)and Apparent Thermal Inertia(ATI)showed the same increasing trend,and the determination coefficient was 0.788.The determination coefficient between ET and ATI was over 0.8,and the spatial distribution of them was consistent.In regions with high ET values,ATI was relatively high.(6)Quantitative analysis of the correlation between meteorological factors such as average temperature,rainfall and wind speed and ATI changes over the years was discussed based on meteorological data from June to September during the period 2002-2016 in Golmud meteorological station.The ATI value increases with the decrease of temperature,the increase of precipitation and the decrease of wind speed,and the corresponding soil moisture content also increases.(7)The ATI is relatively large and the vegetation growth is well when the groundwater depth is 2~3m.The groundwater depth has no effect on surface soil moisture when the water depth is bigger than 15 m and also the ATI is as small as bare soil value. |
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