利用MODIS数据产品进行全国干旱监测的研究

利用MODIS植被指数和陆地表面温度产品建立全国3个农业气候区NDVI-Ts、NDVI-ΔT和NDVI-ATI空间,并由NDVI-Ts、NDVI-ΔT和NDVI-ATI空间分别建立温度植被干旱指数(TVDI)、温差植被干旱指数(DTVDI)和表观热惯量植被干旱指数(AVDI)3个干旱评价指标研究全国干旱分布,利用实测土壤含水量对3个干旱指标进行检验评价.NDVI-ΔT空间中的湿边基本与横坐标平行,表明当土壤水分处于饱和状态或植被完全无水分胁迫条件下,植被和土壤对缓冲环境温度变化的能力大体相当;由NDVI-ATI空间看出,随着植被覆盖增加,表观热惯量有增加的趋势.对比3个干旱评价指标表明:当监测范围较大,区域内地形复杂时,由NDVI-Ts空间计算的TVDI评价干旱最合理,由NDVI-ΔT空间计算的DTVDI在干旱监测中也具有一定的价值,而由NDVI-ATI空间计算的AVDI已经不能合理评价干旱.

Study on monitoring drought in China with MODIS product

In this paper,the 16 days' composite Normalized Difference Vegetation Index(NDVI) and 8 days' composite land surface temperature product in China are used to establish NDVI-Ts,NDVI-ΔT and NDVI-ATI space.From these spaces,temperature vegetation dryness index(TVDI),difference temperature vegetation dryness index(DTVDI) and apparent thermal inertia vegetation dryness index(AVDI) are suggested respectively to evaluate drought in every three agricultural climatic regions in China.The measured topsoil moisture is used to compare with TVDI,DTVDI and AVDI.From NDVI-ΔT spaces,we found that the wet edges are all parallel to the abscissa and the wet soil has the same power to hold back temperature change with the vegetation non-water stress.In NDVI-ATI space,ATI increases with the increase of NDVI.After we compare the measured topsoil moisture with TVDI,DTVDI and AVDI,the result shows that TVDI has a more significant linear correlation with soil moisture than the other two,and TVDI is the most promising method in monitoring drought for large region; DTVDI still has the potential on monitoring drought while AVDI is not competent for monitoring drought.