A global passive microwave based wetness index for the monitoring of soil moisture and inundation

The objective of study is to implement an automated microwave based index to detect and monitor extreme soil wetness and flooding conditions on global scale. The proposed index is based on the Polarization Ratio (PR) that is determined from brightness temperature measures from the AMSR-E sensor. The Robust Satellite Technique (RST) is then applied to the PR to determine a Polarization Ratio Variational Index (PRVI) which is sensitive to extreme hydrological conditions in term of wetness but also drought conditions. The PRVI was determined at different frequencies ranging from the 37 GHz to the 6.9 GHz. The index was tested during extreme flooding events in Asia and Europe as well as in Northern America. The index was implemented globally using observation from passive microwave instruments. The analysis of the results on global scale shows that the index was sensitive to extreme hydrological event and that false alarms were mostly issued over northern snow covered regions only. This implies that the proposed index can be used to assess and delineate flooding conditions.