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

High spectral resolution top of atmosphere brightness temperatures have bee n simulated in the infrared (600-2500 cm(-1)) for an absorbing, emitting mu ltiple-scattering cirrus cloud placed in a realistic atmosphere. The sensit ivity to a variety of assumptions concerning the cirrus cloud properties ha s been studied. The single scattering parameters were characterised using M ie theory for spheres, ray-tracing optics for hexagonal columns and T-Matri x method for spheroids. Simulations have been carried out for various ice c rystal 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 propertie s from data anticipated from the next generation of high-resolution spacebo rne spectrometers such as the Infrared Atmospheric Sounding Interferometer, due for launch on METOP-I in 2003. (C) 1999 Elsevier Science Ltd. All righ ts reserved.