Simulation of high-spectral-resolution infrared signature of overlapping cirrus clouds and mineral dust

Abstract

Numerical simulations have been carried out to understand the effects of overlapping cirrus clouds and mineral dust on the high-spectral-resolution infrared spectrum in the 600-2400 cm-1 region. A combination of the discrete ordinates radiative transfer and line-by-line models that account for the multiple scattering and monochromatic molecular absorption in the atmosphere is utilized to simulate the down-looking infrared spectrum at the top of the atmosphere with a resolution of 0.2 cm-1. It is demonstrated that the spectral slope of the infrared radiance in the 800-1000 cm-1 region can be used to discriminate coexisting cirrus-dust scenes from those associated only with cirrus clouds or dust alone. In a case for a cirrus cloud overlapping with a dust layer, the spectral features in the 1100-1200 cm-1 and 1400-1850 cm-1 regions can be potentially useful for retrieving the optical thicknesses of the dust layer and cirrus cloud, respectively. Copyright 2006 by the American Geophysical Union.