Comparison of SMOS and AMSR-E vegetation optical depth to four MODIS-based vegetation indices

摘要

The main objectives of this study were to provide a proxy "validation" of the Soil Moisture and Ocean Salinity (SMOS) mission's vegetation optical depth product (tau(SMOS)) on a global scale, to give a first indication of the potential of tau(SMOS) to capture large-scale vegetation dynamics, and to contribute towards investigations into the possible use of optical vegetation indices (VI's) for the estimation of tau. The analyses were performed by comparing the spatial and temporal behaviour of tau(SMOS) relative to four MODIS-based VI's, with that of the vegetation optical depth from a similar sensor, AMSR-E (tau(AMSR-E)). 16-day and annual average values of the passive microwave optical depth (tau) for the year 2010 were obtained from SMOS (1.4 GHz) and AMSR-E (6.9 GHz) observations. The VI's chosen for this study were the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Leaf Area Index (LAI) and Normalized Difference Water Index (NDWI).