Monitoring frost disaster of cotton based on difference of vegetation index and canopy temperature by remote sensing

Frostbite can be monitored by remote sensing according to the difference of vegetation index, which has higher spatial and temporal resolution, and to the canopy temperature, which has higher precision of temperature retrieval. Remote sensing is proved feasible in monitoring crop growth, especially after stresses. So combining with the statistical data of agriculture disaster and crop development, according to the difference of NDVI and canopy temperature (CT), the remote sensing was applied to three temporal Landsat ETM images in 2000-08-07, 2001-06-07 and 2001-08-10, the remote sensing monitor the frostbite of cotton happened in Xinjiang Shawan and Shihezi county. The results showed the pixels of the absolute difference of NDVI fallen was 67.8%, the year fallen great than 0.2 was 17%, the percent of difference NDVI decreased within 20%, apparently, the crop status of cotton in 2001 was worse than the year 2000´s. The scatter plot between canopy temperature and NDVI showd the remarkably negative correlation, the correlation coefficient was 20. 63. In the cotton zone, where didn´t affected by frostbite, NDVI increased bigger, the canopy temperature was 26.4°C; where affected faintly by frostbite, the canopy temperature was 27.6°C; where affected seriously by frostbite, the canopy temperature was 29.3°C. Based on the difference of NDVI and canopy temperature, frostbite and the degree of the disaster can be monitored.