A new multi-band temperature retrieval model from fy-3d brightness temperatures

Estimation of surface soil temperature (ST) using passive microwave remote sensing is still a great challenge, especially under diverse land surface conditions. The microwave radiation imager (MWRI) on board Fengyun (FY)-3D satellite is the latest Chinese FY-3 series multiband microwave sensor in orbit, providing a valuable opportunity for estimating surface ST on a global scale. In this study, the FY-3D brightness temperature from 10.7 to 36.5 GHz and the topsoil temperature simulations from ERA5-Land and GEOS-FP from 2019 to 2020 were used to build the Multi-Band Temperature Retrieval Model (MBTRM). The universal global optimization algorithm was employed to establish the MBTRM on a per-pixel basis globally. Ground measurements from a total of 1221 sites worldwide were adopted to fully examine the performance of the proposed MBTRM. Moreover, four widely used passive microwave-based ST models/products were compared. The results reveal the proposed MBTRM performs the best with an averaged root mean square difference (RMSD) of 3.03 K and 3.79 K at descending and ascending overpass respectively and a correlation coefficient larger than 0.9. The advantage of the newly developed MBTRM is that it is user friendly (with explicit formula) and can be applied globally with satisfactory accuracy, and provides a good supplement to optical satellite based temperature products.