An enhanced physical method for downscaling thermal infrared radiance

Thermal infrared (TIR) imagery plays a critical role in characterizing land surface processes and modeling energy balances. However, due to the low TIR radiance emitted from the Earth's surface, TIR imagery acquired from satellite thermal sensors is often with limited spatial resolutions, which presents a serious obstacle to its applications in heterogeneous landscapes (e.g., the studies of urban heat island). In this letter, we developed a new method for downscaling TIR radiance by addressing the limitations of a previously developed physical downscaling method by Liu and Pu (2008). To validate our method, a 990-m TIR image was generated by upscaling a 90-m TIR image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer and downscaled back to the 90-m resolution using the proposed method. The results show that the enhanced physical method not only greatly reduced the block effects and smooth effects found in the original physical method but also improved the downscaling accuracy over the original method.