Drought Monitoring And Warning In The Middle Reach Of Yangtze River

Drought has been seriously concerned by many countries as a natural disaster. How to develop an effective method of drought monitoring and provide reasonable decision and effective measures support for the relevant government departments by remote sensing technology is of great significance. There are many methods using for drought monitoring. The main approaches include traditional drought monitoring and drought monitoring by remote sensing.Two drought monitoring methods are mainly utilized in the middle reaches of the Yangtze River from 2005 to 2010. One is temperature vegetation dryness index(TVDI), and the other is crop water stress index(CWSI). The paper is organized as follows:1) Establish the NDVI-LST feature space using NDVI and LST products. Then calculating the TVDI index by using temperature vegetation dryness index model to drought monitoring research.2) Using products of MODIS and meteorological data to calculate component of Surface energy balance by SEBAL model. Then calculating daily evapotranspiration. Finally verified evapotranspiration in the study area.According to Priestley-Taylor model using MODIS image and meteorological data to calculate the potential evapotranspiration in the study area.3) Daily evapotranspiration and potential evapotranspiration are calculated by SEBAL model and Priestley-Taylor model in the study area. Then calculate the CWSI index by using crop water stress index model to drought monitoring research.4) Drought early-warning index is established basing on soil moisture, the change trend of drought and precipitation anomaly percentage. Drought warning of research area by the drought early-warning index is made.By comparing and analyzing the drought monitoring results of the two algorithms mentioned above, it is found that:the maximum difference is 14.24 percent, and the minimum is 0 between TVDI and CWSI. Absolute value of the difference between CWSI and TVDI which divided by CWSI, the maximum is 300 percent. It is a severe drought, because the percentage of dry weight is very small, resulting in a large error and the minimum is 0.The majority of the area is normal which ranges from about 30 percent to 70 percent. Area of light drought is about 20 percent to 40 percent.From the perspective of time, drought of study area is the most serious in every March. Area of drought is about 67.86 percent(Light drought accounts for 41.87, moderate drought accounts for 23.7 percent, severe drought accounts for 2.29 percent). At the end of May, area of drought is about 56.86 percent(Light drought accounts for 23.28 percent, moderate drought accounts for 30.94%, severe drought accounts for 2.64 percent). Drought is eased, light drought reduces 18.59 percent, moderate drought increase 7.24 percent, severe drought is about no change. But from the beginning of September the drought aggravated gradually. Area of drought is about 62.34 percent(Light drought accounts for 46.56 percent, moderate drought accounts for 15.7 percent, severe drought accounts for 0.06 percent). Light drought increase 9.21 percent, moderate drought increase 2.76 percent, severe drought is about no change.From the perspective of spatial, no matter TVDI or CWSI, the study area of low degree arid areas is mainly distributed in the northwest and southwest which is about 30 percent. In March, parts of Xiangfan in the northwest of China are in dry condition. Severe drought area is mainly distributed in the east and south with the proportion of 20 percent. Supply and demand balance of soil moisture in the eastern part of Ji’an in May.