Abstract: The satellite-derived microwave land surface Emissivity Difference Vegetation Index (EDVI) is a good indicator of vegetation water content (VWC). And it can be used under a cloudy sky and over dense vegetation areas where satellite optical vegetation index can be easily saturated. Previous studies on EDVI used the two frequencies of 19 and 37 GHz only. The associated EDVI can only represent VWC in one single layer of the canopy. Measurements from Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) onboard NASA’s Aqua satellite provided multiple choices of satellite remote sensing VWC with EDVI. In this study, multiple source measurements, including microwave brightness temperature from AMSR-E, cloud parameters from Moderate-resolution Imaging Spectroradiometer (MODIS), and reanalysis of atmosphere states from ECMWF were synergized, to retrieve the microwave land surface emissivity at 6.925, 10.65, 18.7 and 36.5 GHz in eastern and southeastern Asia from 2003 to 2010. The retrievals were then used to define multiple channel EDVIs of EDVI(6v, 37v)，EDVI(10v, 37v) and EDVI(18v, 37v) and the characteristics of those EDVIs over forest and cropland areas were studied. The results showed that, EDVI(6v, 37v) and EDVI(10v, 37v) are greater than EDVI(18v, 37v) in forest dominated areas. This is most likely due to the fact that the penetration depth of EDVI(6v, 37v) and EDVI(10v, 37v) are deeper than that of EDVI(18v, 37v), thus indicating relatively more VWC in thicker canopy layer of the forest. The differences among the three EDVIs can be used to represent the vertical distribution of VWC in upper, middle and lower layers of high and dense vegetation. However, for the shallow and sparse vegetation without significant vertical variation of VWC, the differences among the three EDVIs are too small to be used.

Key words: satellite remote sensing, microwave land surface emissivity, emissivity difference vegetation index(EDVI), vegetation water content, vertical structure of vegetation