A water vapor scaling (WVS) method for improving atmospheric correction of thermal infrared (TIR) data

Abstract

The thermal infrared (TIR) radiance at sensor measured by any spaceborne or airborne instrument will include atmospheric emission, scattering, and absorption by the Earth’s atmosphere. These atmospheric effects need to be removed from the observation in order to isolate the land-leaving surface radiance contribution and retrieve important surface variables such as land surface temperature (LST) and emissivity. The accuracy of the atmospheric correction is dependent upon accurate characterization of the atmospheric state using independent atmospheric profiles of temperature, water vapor, and other gas constituents. The profiles are typically input to a radiative transfer model for estimating atmospheric transmittance, path, and sky radiances. Residual errors from incomplete atmospheric correction constitute one of the largest uncertainties in derived LST and emissivity products from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on NASA’s Terra satellite. This chapter will describe a technique for improving the accuracy of the atmospheric parameters on a pixel-by-pixel basis using the Water Vapor Scaling (WVS) method. We have shown that using WVS can improve the accuracy of LST retrievals by up to 5 K for MODIS and 3 K for ASTER data in humid conditions.