Cirrus cloud top-of-atmosphere radiance spectra in the thermal infrared

High spectral resolution top of atmosphere brightness temperatures have been simulated in the infrared (600-2500 cm(-1)) for an absorbing, emitting multiple-scattering cirrus cloud placed in a realistic atmosphere. The sensitivity to a variety of assumptions concerning the cirrus cloud properties has been studied. The single scattering parameters were characterised using Mie theory for spheres, ray-tracing optics for hexagonal columns and T-Matrix method for spheroids. Simulations have been carried out for various ice crystal sizes, shapes and size distributions. A statistical method has been used on the simulated spectra to suggest combinations of wavelengths which might best be exploited for the retrieval of cirrus cloud optical properties from data anticipated from the next generation of high-resolution spaceborne spectrometers such as the Infrared Atmospheric Sounding Interferometer, due for launch on METOP-I in 2003. (C) 1999 Elsevier Science Ltd. All rights reserved.