IMARS Mineral Dust and Ice Cloud Retrieval for IASI

Mineral dust and ice cloud optical depth at 10µm is retrieved over land and ocean with a probabilistic trispectral brightness temperature differnce apporoach based on pseudo-channels. It makes use of a range of mineralogical compositions and particle size distributions for mineral dust as well as different crystal shapes and size distributions for ice clouds. With this information optical depth is also transferred to the traditional AOD wavelength of 550nm. As terrestrial infrared spectral variability information is used in the retrieval, it is sensitive to (silicate) dust particles only. The probabilistic brightness temperature difference approach allows for dust AOD retrieval also over desert surfaces with highly variable surface emissivity. As only observations of the 8-12µm range are used, the retrieval is independent of solar illumination, thus yielding dust observations twice daily. A pixel-wise retrieval error and dust probability are as well calculated. Validation results are documented in the Algorithm Theoretical Basis Document.The IMARS results also contain retrieved cloud information (optical depth, effective radius, ice water path, cloud top temperature).