Active and passive microwave data improve soil moisture estimates



Assimilating satellite observations from active or passive microwave sensors into models can improve soil moisture estimates, a new study shows. Passive sensors detect radiation emitted naturally from the land surface, while active sensors emit a radiation pulse toward the Earth surface and measure the energy reflected back to the satellite.Draper et al. assimilated soil moisture derived from the active Advanced Scatterometer (ASCAT) and passive Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) satellite sensors into a land surface model and assessed the resulting soil moisture estimates against in situ observations from 85 sites in the United States and Australia. The researchers found that the active and passive microwave data similarly improved the model's soil moisture estimates. Following the recent failure of AMSR-E, the new study shows that systems designed to assimilate AMSR-E soil moisture can switch to ASCAT data without loss of accuracy. Improved soil moisture estimates could be useful for applications such as weather and drought forecasting. (Geophysical Research Letters, doi:10.1029/2011GL050655, 2012)