Research Project: Study of Dust Aerosol Optical and Microphysical Properties Based on Combined Spaceborne Lidar and Polarimetry Observations
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Deserts around the world emit tons of dust aerosols into the atmosphere. Except for playing a role in earth’s materials cycle, dust aerosol has been found to significantly impact the earth energy budget by acting as direct and indirect radiative forcings. The complexity of dust aerosol optical and microphysical properties leads to large variety of dust aerosol radiative effect. Current radiative transfer simulation and climate modeling usually assume constant dust aerosol property because of little knowledge of its variability. To reduce the uncertainties, it is necessary to have a quantitative understanding of spatial and temporal variability of dust aerosol properties. We propose to use combined observations from spaceborne lidar and polarimeter, together with modeling capabilities to study the variability of dust aerosol optical and microphysical properties including optical thickness, absorptive ability, effective particle size, and particle nonsphericity. Lidar is able to measure the vertical profile of dust aerosol backscattering. Our preliminary findings suggest that the lidar signal is not only sensitive to dust aerosol optical thickness and nonsphericity, but also sensitive to effective particle size. However, those dust aerosol properties cannot be determined uniquely only from lidar observation due to nonsufficient a priori knowledge. Multi-channel and multi-angle polarization measurement will provide more information of particle size and optical thickness. The latest Decadal Survey report prioritizes the observations of aerosol properties and vertical profile with backscatter lidar and multi-channel and multi-angle polarimeter. The proposed study is highly relevant to NASA and is in alignment with the concept by using combined spaceborne lidar and polarimetry observations to study dust aerosol optical and microphysical property variability.
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