Detection and retrieval of mineral dust aerosol using AERI during the UAE2 field campaign

A method for detecting and retrieving airborne mineral dust using the surface-based Atmospheric Emitted Radiation Interferometer (AERI) has been developed using radiance data collected during the United Arab Emirates Unified Aerosol Experiment (UAE2) at Al Ain UAE, during the period of August 13 – September 30, 2004. Taking advantage of the high spectral resolution and zenith viewing capability of the AERI instrument, absorptive differences in the thermal IR window along prescribed micro-window channels are exploited to differentiate dust from cirrus clouds. Assuming a specified dust compositional model a priori, and using the T-matrix and FDTD light scattering programs for oblate spheroids and tetrahedrons, respectively, a technique for retrieving dust size parameter and optical depth has been implemented. The potential for retrieving mineral composition is also being investigated. Four dust compositional models representative of the average soils found in the global deserts ranging from quartz to various clays, including external mixtures of the minerals, are evaluated to determine the optimal fit with the observed radiance fields. Validation of the retrieved optical and microphysical parameters is achieved through inter-comparison with those from a collocated AERONET sun-photometer.