A downscaling method for distributing surface soil moisture within a microwave pixel: application to the Monsoon ’90 data

A downscaling method of the microwave surface soil moisture is applied to the PBMR data collected during the Monsoon ’90 experiment. The downscaling method requires (1) the coarse resolution microwave observation (2) the distribution at fine scale of soil temperature and (3) the distribution at fine scale of the surface conditions composed of atmospheric forcing and the parameters involved in the modeling of land surface-atmosphere interaction. During the Monsoon ’90 experiment, Preprint submitted to Elsevier Science 10 September 2005 eight ground-based meteorological and flux stations were operating over the 150 km2 study area simultaneously with the acquisition of the aircraft-based L-band PBMR data. The heterogeneous scene is hence composed of eight sub-pixels and the microwave pixel is generated by aggregating the microwave emission of all sites. The results show a good agreement between the downscaled and ground-based soil moisture as long as the intensity of solar radiation is sufficiently high to use the soil temperature as a tracer of the spatial variability of surface soil moisture.