An atmospheric influence correction method for longwave radiation-based in-situ land surface temperature

Abstract

Obtaining in-situ land surface temperature (LST) with thermal infrared or longwave radiometers for validating satellite LST, namely the radiation-based method, is one of the most widely used approaches. Due to the relatively short path lengths, the near-surface atmosphere contribution is generally ignored in radiation-based in-situ LST measuring for narrowband radiometers. However, it is necessary to investigate the influence for broadband radiometers. In this study, nine stations in China are selected to quantify the atmospheric influence. Furthermore, a correction method combining the Radiative Transfer Equation and Multi-Layer Meteorological Parameters (RTE-MLMP) is proposed to correct the influence on radiation-based in-situ LST. Results show that the influence follows diurnal patterns and seasonal differences. Depending on the station, ignoring the near-surface atmosphere influence can cause in-situ LST to be overestimated (underestimated) by up to 3.11 (1.21) K at nighttime (daytime). For the RTE-MLMP method, the key is to estimate the near-surface atmospheric transmittance (τNS) and radiance (LNS) and to establish equations for each station. Results show that the mean and standard deviation (STD) of the error are both lower than 0.001 for the estimated τNS, and lower than 0.1 W/m2 and 0.6 W/m2 for the estimated LNS, respectively. Then, the in-situ LST is corrected with the estimated τNS and LNS. The resulting LST mean and STD of its error are both lower than 0.1 K, which is significantly lower than ignoring the near-surface atmospheric influence. Our further analysis suggests that single-layer meteorological parameters can only be used when the installation height difference between the meteorological sensor and the long-wave radiometer is within 3 m. Since the correction method relies on readily available meteorological data, further research should focus on the generalizable coefficients or strategy for atmospheric correction to enhance the accuracy of radiation-based in-situ measured LST.