Development of a Global Infrared Land Surface Emissivity Database for Application to Clear Sky Sounding Retrievals from Multispectral Satellite Radiance Measurements

TLDR

MOD11 provides emissivity at only three spectral regions, insufficient for the higher‑resolution emissivity required for accurate atmospheric temperature and moisture retrievals from satellite IR sounders. The study introduces a global IR land surface emissivity database to improve atmospheric temperature and moisture retrievals from multispectral satellite radiances. The database is constructed by applying a baseline fit model, informed by MODIS MOD11 and laboratory measurements, to interpolate emissivity across 10 hinge wavelengths (3.6–14.3 μm) and fill spectral gaps between MOD11’s six bands. The resulting database provides 10‑wavelength, 0.05° global emissivity, and its use in MODIS IR regression retrievals yields improved atmospheric moisture profiles compared to assuming constant emissivity.

Abstract

Abstract A global database of infrared (IR) land surface emissivity is introduced to support more accurate retrievals of atmospheric properties such as temperature and moisture profiles from multispectral satellite radiance measurements. Emissivity is derived using input from the Moderate Resolution Imaging Spectroradiometer (MODIS) operational land surface emissivity product (MOD11). The baseline fit method, based on a conceptual model developed from laboratory measurements of surface emissivity, is applied to fill in the spectral gaps between the six emissivity wavelengths available in MOD11. The six available MOD11 wavelengths span only three spectral regions (3.8–4, 8.6, and 11–12 μm), while the retrievals of atmospheric temperature and moisture from satellite IR sounder radiances require surface emissivity at higher spectral resolution. Emissivity in the database presented here is available globally at 10 wavelengths (3.6, 4.3, 5.0, 5.8, 7.6, 8.3, 9.3, 10.8, 12.1, and 14.3 μm) with 0.05° spatial resolution. The wavelengths in the database were chosen as hinge points to capture as much of the shape of the higher-resolution emissivity spectra as possible between 3.6 and 14.3 μm. The surface emissivity from this database is applied to the IR regression retrieval of atmospheric moisture profiles using radiances from MODIS, and improvement is shown over retrievals made with the typical assumption of constant emissivity.