A consistent record of vegetation optical depth retrieved from the AMSR-E and AMSR2 X-band observations

Vegetation optical depth (VOD) retrieved from microwave remote sensing techniques has been used as an important proxy for monitoring the vegetation dynamics at large scales. In a first study we developed new X-VOD indice inversion of X-MEB model Microwave Scanning Radiometer 2 (AMSR2, 2012-present) observations. The Advanced EOS (AMSR-E, 2002–2011) and AMSR2 share many characteristics, such local crossing time, incidence angle, frequency X-band, etc, which makes it possible to produce consistent long-term product over long period spanning 2002 present. objective this was merge AMSR-E observations in order, second step, combined periods AMSR2. main challenges retrieving data set are that (i) there is bias between two sensors; (ii) lack overlapping sensors impossible achieve direct inter-calibration. Here, overcome problem, slow rotation (AMSR-E L1S), similar characteristics provided concurrently with AMSR2, bridge calibrate brightness temperature (TB) TB. As our TB calibration AMSR-E/AMSR2 product, evaluated based on different inter-calibration, either global-based or pixel-based, methods. Both were against Aboveground Biomass (AGB), Leaf Area Index (LAI) Normalized Difference (NDVI). results suggest inter-calibration methods using homogeneous temporally stable land covers (Evergreen Broadleaf Forests Snow Ice) reference sets best results. For instance, spatial relationships AGB/LAI/NDVI highly after work. This laid solid foundation X-VOD, AGB, (almost 20 years).