FASTEM - SMOS Evaluation

L-band SMOS brightness temperature measurements have been monitored for a long time at ECMWF using the Community Microwave Emission Modelling Platform (CMEM) forward model. CMEM is a well-established model to simulate L-band measurement over land. Over inland water bodies, coastal areas and open ocean, instead, a simplified emissivity model is used that does not account for the wind and foam dependent emissivity changes. L-band measurements over the ocean are known to be sensitive to high winds and could provide Numerical Weather Prediction (NWP) systems with wind information not given by other higher frequency passive measurements or active instruments.
In this study a preliminary analysis is carried out to investigate the use of an alternative forward model operator, RTTOV-FASTEM, over the ocean. RTTOV is widely used in the NWP community to simulate brightness temperature for high frequency passive instruments. FASTEM is the ocean emissivity model  that recently was extended to L-band. It takes account the effects of the wind induced ocean roughness and foam on the brightness temperatures. In this study the simulated SMOS brightness temperatures over the ocean have been generated using RTTOV-FASTEM and for the first time compared to CMEM simulations. The SMOS departures have been evaluated for the two forward models.
This report presents the results of the work done in the framework of the ESA contract
4000101703/10/NL/FF/fk CCN6, WP400.