Multi-sensor SAR data for improved modeling of microwave brightness temperature over boreal forest

Here, we investigate multiple ways of assimilating synthetic aperture radar (SAR) data to L-band Microwave Emission of the Biosphere (L-MEB) model to enhance the model performance over forested areas in the boreal zone. L- and C-band satellite SAR backscatter data, X-band interferometric SAR coherence, as well as auxiliary data layers from forest authorities are used as a proxy in calculating the forest transmissivity, instead of traditionally used leaf area index (LAI) parameter. Our earlier experiments have shown, that when particularly ALOS PALSAR (L-band) and multitemporal composite Sentinel-1 (C-band) data were applied, an improved agreement was achieved between the measured and simulated brightness temperatures (TBs) over forests. Here, we extend our analysis and examine data acquired by ALOS PALSAR, ESA Sentinel-1, and TanDEM-X mission of DLR, as well as several other auxiliary datasets on forest parameters. Our proposed model based approach indicates the potential of an SAR-based estimation of forest volume transmissivity and represents a viable way of active-passive microwave satellite data fusion and incorporating readily available reference data.