Spatiotemporal Variation Of Soil Moisture In Arid Area Based On VIC Land Surface Model And Remote Sensing

Large-scale,long-term sequence and high-precision research on soil moisture has important scientific guiding significance for improving drought early warning ability,ecological environment restoration ability and precision agricultural development.With the development of remote sensing technology and land surface process model,people realize that remote sensing monitoring soil moisture has the advantages of large range and high time efficiency,but the underlying surface heterogeneity and weather impact are the biggest problems in monitoring,combined with land surface processes.For the simulation of soil moisture continuity and authenticity,the combination of remote sensing technology and land surface process model simulation can more accurately study the change pattern of soil moisture in spatiotemporal variation.Based on Landsat TM data and VIC land surface process model,this paper uses Wei-Ku Oasis as a typical drought-like area,using geostatistics,3S technology,numerical simulation,land use classification method,From the perspective of VIC model simulation and TVDI remote sensing monitoring,the spatiotemporal variation of soil moisture in different seasons in the study area from 2008 to 2016 was discussed.Analysis of irrigated area and crop water demand,land use area change impact on simulation results.The accuracy and verification were compared with the measured data.The following were the main research results:(1)In the past ten years,the area of cultivated land and saline land had increased significantly,and rainfall and temperature changes have been flat.Using the land use transfer matrix to analyze the changes in the four land types in the oasis,from 2007 to 2017,the area of cultivated land and saline land had increased by more than 35%,the area of wasteland had decreased by 46% compared with 2009,and the area of shrub land had increased by about 15%.The trend of land desertification in the study area had been reversed and the overall ecological environment had been improved.(2)The TVDI model better reveals the temporal and spatial changes of soil moisture content in the study area.From 2008 to 2016,in spring,the overall TVDI value was below 0.37,the wet area was close to the northern part of the oasis;the summer TVDI value was above 0.5;in autumn,the TVDI value in the oasis was greater than the outer moisture content of the oasis by 22.12%,and the external moisture content had a decreasing trend.(3)From the perspective of space,From January to June,the soil moisture content in the southwestern region was about 11% lower than that in the northeast region;From July to September,the soil moisture content in the northeastern region of the study area was generally higher than 35.21 mm,and the arid region was concentrated in the southwest,northwest and south regions;from October to December,The southwestern region was generally 13% lower than the soil moisture in the northeastern region.From the perspective of space,The surface soil moisture content of saline soil was about 0.06% higher than that of cultivated land.In the rainy season,the soil moisture content of shrub soil was about 0.02% higher than that of the other three types of land.During the dry season,the soil moisture content of wasteland was at a low value of 28.41 mm.In the rainy season,the soil moisture content increased to a high value of about 56.78mm;due to the conversion of a large amount of wasteland into cultivated land,the soil moisture content of the oasis wasteland and the cultivated soil were close to each other,between 28.784 and 53.741 mm.The simulated soil moisture value of cultivated land VIC responds well to the monthly change of crop water requirement(4)Combining the temporal coupling degree of the two models,the soil moisture content of shrubs and saline soils was higher than that of cultivated land and wasteland,and the dry and wet changes were obvious,and the abnormal years were less;the VIC simulation curve of soil moisture content of cultivated land and wasteland had a large variation range and more abnormal years.In the field of soil moisture measured in different years and its VIC simulation value R2 was above 0.34,the simulation accuracy was reliable.In this study,the advantages of refinement simulation of land surface process model provide solid data support for water and salt scenario simulation and salinization dynamic prediction in arid areas.