Study On Inversion Model Of Drought In Zhangwu Area Based On HJ Satellite Data

The research region is Zhangwu County of Liaoning Province, and it is based on HJ satellite that can provide multi temporal and multi spectral remote sensing data from July to September in 2014, and combined with meteorological data that provide by the China Meteorological Resources Network and the data obtained from field sampling. ENVI and ArcGIS platform are used to fine processing of the remote sensing data such as radiometric calibration, geometric correction, atmospheric correction and compute the related parameters like surface temperature, vegetation index and so on.Construct the two dimensional space about temperature and NDVI to obtain the related temperature vegetation drought index, infrared band and near infrared band to obtain perpendicular drought index and modified perpendicular drought index which is combined with vegetation coverage.Fitting analysis of the soil water content at 10cm under the surface and the above three indices. Select the most relevant model as the based model and modifiy, resulting in drought monitoring model for Zhangwu area. The model is applied to the soil moisture condition, as the evaluation index, obtaining drought grade distribution in Zhangwu area in 2014. The main conclusions of this study are as follows:(1)In the process of calculating the surface temperature, the Artis algorithm is selected to retrieve the surface temperature. The change tendency of inversion temperature is basically the same with the measured result, and the inversion value is lower than the measured value. The vegetation coverage is calculated by the dimidiate pixel model,and using the SEBS model to obtain the evapotranspiration. The computational difficulty of retrieving soil moisture is reduced, and the model is easier to use.(2)The perpendicular drought index, the modified perpendicular drought index and the temperature vegetation drought index are fitted to the soil moisture at 10cm under the surface respectively. The results show that the determination coefficient R2 of these three kinds of index and the soil moisture are about 0.15,0.3 and 0.45. The correlation between the temperature vegetation drought index and the soil moisture is the highest, so it is feasible to take the temperature vegetation drought index as the basic model.(3)The soil type is more complex in Zhangwu. In order to eliminate the influence of surface soil, the enhanced vegetation index is selected as the factor to modify the temperature vegetation drought index. The model of summer drought monitoring in Zhangwu area is raised by the inversion index and the measured soil moisture data in July 14th and August 6th in 2014, the data in September 18th is used to verify the model, the correlation coefficient of this model is-0.770, the significant correlation at 0.01 level and the model accuracy is up to 85%.(4) According to the inversion results of the model, the distribution map of the drought in Zhangwu area is obtained, and the drought situation is analyzed.The drought situation is the lightest in July 14th 2014, there are more than 35% of the regions express the light drought state.The drought situation is the most serious in August 6th, more than 44% of them are in the state of severe drought, and the drought situation is eased in September 18th.