This soil moisture data set is based on dual-polarization brightness temperature measurements carried out with the polar orbiting Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) at frequencies of 6.9 GHz, 10.7 GHz, and 36.5 GHz. A radiative transfer model is used to simulate the brightness temperature based on the soil surface and canopy emissivity and the surface temperature which is derived using the AMSR-E 36.5 GHz data. Simulated brightness temperatures are compared to the measured ones while iteratively changing the variable parameters until convergence is achieved. The parameters are the soil dielectric constant (depends on soil type and moisture) and the canopy optical depth (depends on canopy type, density, and water content). Once convergence between modeled and measured brightness temperature is achieved (difference below 0.25 K) the soil moisture is derived using a soil dielectric mixing model and a global data set of soil physical properties. The derived quantity is the relative volumetric water content and is given in percent. Soil moisture (and its uncertainty) is computed for both frequencies (6.9 GHz and 10.7 GHz) separately.
We offer data for years 2002-2011, i.e. the full AMSR-E measurement period. Data are offered as daily swath composites, separated for descending and ascending overpasses, i.e. there are two files per day available; one contains data from all ascending overpasses of the respective day, the other data from all descending overpasses. In principle the data set offered here via ICDC is a re-formatted (1), inconsistency-corrected (2) version of the LPRM_AMSRE_SOILM3_V002 data set of the VU Amsterdam.
(1) Soil moisture data are now in landscape mode
(2) Inconsistencies w.r.t. scale factors are corrected. In addition the netCDF-files are following the more recent CF conventions now.
Last data set update (re-formatting): August 6, 2015.