Spaceborne lidar aerosol retrieval approaches based on improved aerosol model constraints

Abstract

Aerosol retrievals at 532 nm for the current GLAS and upcoming CALIPSO satellite lidar missions employ/will employ a table look-up approach to select climatologically based S/sub a/ model values for these retrievals when alternate, less uncertain methods for either defining S/sub a/ (the aerosol extinction-to-backscatter ratio, or aerosol lidar ratio) or providing the needed auxiliary information are unavailable. Reagan et al. (2004, 2005) addressed a revised table look-up approach that incorporated two notable revisions for improved S/sub a/ selection, which, as a consequence, enable more bounded aerosol retrievals. One is a refined, more bounded set of S/sub a/ values, both for 532 nm and 1064 nm, representative of a definitive set of aerosol types/models determined from an extensive analysis of the AERONET database. The other is an accompanying set of key spectral ratio parameters (i.e., dual wavelength, 532 nm to 1064 nm, ratios of backscatter, extinction and S/sub a/) also derived from the AERONET data which offer additional ways to bound the lidar aerosol retrievals. Thus, aerosol retrievals can be obtained subject to the constraints that the lidar data yield retrievals with spectral ratio parameters consistent with a given aerosol model (or models), to confirm the model choice and better bound the retrievals. This paper presents the simulation results made by assuming different models in support of the two-wavelength lidar constrained ratio aerosol model-fit (CRAM) retrieval approach. In addition, a performance function and multiple scattering corrections based on LITE signals are also investigated.