Research On Agricultural Drought Monitoring Based On Ts-NDVI Space Of Chongqing

Drought is one of major natural disasters that happens frequently inworld-wide inrecent years, they not only disturbed social and economicsustainable developmentseriously,but also affected agriculture especially. In the southwest of China,due to thecomplicated terrain condition,poor capacity of waterstorage in soil，uneven spatial andtemporal distribution of rainfall and so on,regional and periodicdroughts often occur inChongqing.It brings great losses to the agricultural production and nationallives.Compare with the traditional agricultural drought monitoring,remote sensing ismore and more applied in agricultural drought monitoring for its fast,efficient,low costand other characteristics.Therefore,it has an important practical significance on makinguse of3S technology(GIS,GPS,RS)to monitor drought information,assess drought,takepositive and effective measures to minimize losses,timely and accurately.Land surface temperature and vegetation index has the close relationship with thevegetation physiology and growth,so they have become the important indexes ofagricultural drought monitoring. But only one index for drought monitoring will cause aproblem which reduces the accuracy and usefulness of the drought monitoring becauseshort-term vegetation subjected to water stress can maintain the original green time. Sothe methods which use two indexes become an important direction of current droughtmonitoring.In this paper, using MODIS land surface temperature data and surface reflectivitydata between May and September from2000to2011to retrieved TVDI in thewesternregion of Chongqing, and analyze the relationship between TVDI with Ts,NDVI and meteorological precipitation data as well as its spatial variability inter-month,inter-annual change. The conclusions are as follows:(1) The study area of Ts-NDVI feature space dry and wet edge are not a straightline at all, and there are similar shapes of dry or wet edge in different feature space; theslope of dry and wet edge changes with the NDVI values.(2) There are some relationships between TVDI with Ts, NDVI and meteorological precipitation data; we can conclude that temperature vegetation drought index isreasonable to indicate the evaluation of drought. From the correlation of TVDI and Ts,NDVI showed that TVDI and Ts has a significant positive correlation, TVDI and NDVIhas a negatively correlation.TVDI with the precipitation showed that the data changetrend has a contrary trend with the increase of TVDI values.(3) From month change of Chongqing from2000to2011, we can find that therewas little change in the wet areas of northern of region; the drought was light dry andsevere dry in the western region of Jilin Province at May and June and it was easy tocause the spring drought；With the development, the middle dry and severe dryincreased between July and September, and the normal and light dry reduced at thesame time.Summer drought is always happened in Chongqing.(4) The inter-annual variability from2000to2011analysis showed that, the regionwas mainly in middle drought and severe drought. And the drought changed with lightdrought to severe drought from northeast to southwest,especially in west ofChongqing.Between2000and2011, there were the biggest areas of the light drought,middle drought and the severe drought in2006, three areas were accounted for90.54percent of the region.