The Study, Based On Modis Remote Sensing Monitoring Of The Drought In Shaanxi Province

The drought monitoring in Shaanxi province which was based on the NOAA data has been developed for nearly 10 years.Looking from the practical application effect of the previous years,it has mainly solved the dynamic monitor problems of the occurrence and development in the entire province macroscopically,but it can't meet the services demand of the city and the county governments.Especially in Shaanxi province,from south to north,the climatic conditions,geology, surface vegetation cover and planting systems have great differences,which requires refinement of drought monitoring and assessment.MODIS data has more significant advantages than the NOAA data in wave band and explore precision.With the widespread use of MODIS data,how to achieve the refinement of the drought monitoring using MODIS date has become an important developing direction of remote sensing quantitative application,and which is also the key issue in this paper.On the basis that the research achievements and experiences on drought monitoring models being widely summarized,and on the view of can be operated and applied,we carded on the operational research methods about Shaanxi province drought remote monitoring by using the method of thermal inertia and vegetation supply water index based on the MODIS data.First,MODIS-1B datas are preprocessed by the way of atmospheric correction,Bow-tie effect processing,projection transformation,geometric correction and so on.Based on this carried on the key parameter inversion,using the two-phase daily MODIS data of day and night,we established the thermal inertia remote sensing monitoring model.The thermal inertia model belongs to the quota expression method.And usually,the real thermal inertia is replaced by the apparent thermal inertia. We calculated the apparent thermal inertia ATI through the expression ATI=B(1-ABE)/ΔT,then gain the correlation analysis about ATI and the soil moisture value.The conclusion is,in the three models,the exponential model is the best,the line model is the second,and the logarithm model is a little less.But the three kinds of model have all achieved the relevant level,in the view of the fact that the linear model computed easily,the linear model is chose frequently in the actual monitor.The drought situation rank division is as follows:heavy drought Y≤40;drought 40＜Y≤50;light drought 50＜Y≤60;not dry 60＜Y≤80;moist Y＞80.Vegetation supply water index model only needs a phase of information.This paper has first divided the drought monitoring district into five parts on the basis of climate characteristic,NDVI and LST were selected as input parameter.And each day's vegetation supply water index VSWI was calculated through the expression VSWI=T_s/NDVI,then the ten-day period largest vegetation supply water index can be obtained through the computation,use the monitoring dates of soil moisture on the ground in every monitoring area as the calibration spot,according to the division standard about drought situation of agriculture meteorology,each district's vegetation supply water index is divided into five ranks to reflect the relative degree of drought.Selects May 2007 MODIS satellite remote sensing date to carry on the confirmation,draws a conclusion,the monitor result of this method is quite match with the actual drought situation.Looking from the findings,the results of using MODIS data for drought remote sensing monitoring are basically consistent with the ground actual observation results and its accuracy is higher,what's more,its visualization effect is batter than NOAA satellite.It can live up to the requirement of Shaanxi province's drought monitoring considering of operation and application,not only has an access to the province drought monitoring macro information,but also can obtain drought monitoring refinement products from a variety of cities and counties according to the physical service demand.