A NEW METHOD FOR DROUGHT MONITORING BASED ON LAND SURFACE ENERGY BALANCE AND ITS PRELIMINARY APPLICATION TO THE HEDONG REGION OF GANSU PROVINCE

Current drought monitoring methods based on remote sensing technique generally are not of high precision. Seeking a new remote sensing drought monitoring technique is of great help to improve and develop the technique of drought monitoring and alert. The Bowen ratio, the ratio of sensible heat flux against latent heat flux, and reflecting surface hydro-thermal characteristics can be tentatively utilized for drought monitoring. Using EOS-MODIS satellite data and synchronized meteorological data, the Bowen ratio drought monitoring model was established based on surface energy balance. Then, the correlation between soil moisture against Bowen ratio index (β) and temperature-vegetation index (TVX) was analyzed. Finally, taking the clear-sky imagery (October 5, 2014) as an example, a drought level classification standard based on β was established and droughts in the study region were evaluated. Results show that β is highly negatively related to soil relative humidity, which has a better correlation than that between TVX and soil relative humidity in the depth range of 0∼20 cm. The precision of drought monitoring is significantly improved. The distribution of dry-wet condition based on the β drought classification standard is well consistent with the distribution of antecedent precipitation over the study region. Evaluation results show that generally no drought took place over the study region on October 5, 2014, which is consistent with precipitation anomaly percentage for the period of September, 2014. Our study suggests that the surface energy balance based Bowen ratio index can achieve excellent results when applied to drought monitoring and has a good application prospect.