Analysis of OMI Aerosol Retrievals with Coincident and Collocated Observations By MODIS and Caliop over the Ocean

Abstract:

When observing aerosols from space in the UV range , the upwelling radiation is dependent not only on the aerosol intrinsic properties but also on the location of the aerosol layer in the atmospheric column. In the current operational retrieval by the OMI 2-band algorithm (OMAERUV), the aerosol height is assumed and the aerosol optical depth (AOD) and single scattering albedo (SSA) at 388nm are derived. Since the sensitivity to aerosol altitude occurs only at UV wavelengths, it suggests that if the AOD is known a priori, the associated SSA and aerosol height can be derived. The theoretical approach and first applications of this method has been explored previously by combining OMI with MODIS AODs (extrapolated to the OMI’s wavelengths) over the ocean. However, no detailed studies have been carried out by comparing with independent measurements such as those from the CALIPSO lidar.

This poster will show detailed case studies of collocated and simultaneous observations of aerosol height (from the space borne lidar CALIOP) and AOD (from MODIS-Aqua) with the objective to evaluate the aerosol height assumed and the AOD at 500nm derived by OMAERUV. The cases were selected in areas known for biomass burning (off the coast of South Africa-Madagascar) and for dust and dust mixed with smoke (such as off the coast of Dakar). By comparing with Calipso, this analysis will highlight the sensitivity of OMAERUV retrievals to aerosol layer thickness and location in the atmospheric column, both parameters currently assumed by the retrieval algorithm.