Effects Of The Atmosphere And Surface Emissivity On The Thermal Infrared Spectral Signature Measured From Modis-n

We simulate effects of the atmosphere and surface emissivity on the thermal infrared spectral signature in six proposed thermal channels, for measurements of surface temperature, of MODIS-N (Moderate Resolution Imaging Spectrometer Nadirmode). Conditions for the simulations include a variety of atmospheric profiles over a wide elevation range, with difkrent visibilities near the Earth’s surface under cloud-free conditions. Calculated or measured spectral emissivities for various land surfaces-snow, clay, coarse sand and fine sand-range from 0.55 to 1.0. The upwelling band-averaged radiance at the top of the atmosphere can be exprcssed with three terms: surface emittance, reflection of the downward radiance at the surface, and the atmospheric path radiance. The model separates effects of surface temperature and emissivity from those of the atmosphere; it also includes effects of solar radiation on the medium wavelength infrared bands from 3.5 to 4.lp.m. This parameterized model is useful for development of practical algorithms for deriving surface temperature and emissivities from multi-channel MODIS-N thermal data.