Novel Aerosol Extinction Coefficients and Lidar Ratios over the Ocean from Calipso Cloudsat: Evaluation and Global Statistics
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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Aerosol extinction coefficients sigmaa and lidar ratios LRs are retrieved over the ocean from CALIPSOs Cloud-Aerosol Lidar with Orthogonal Polarization CALIOP attenuated backscatter profiles by solving the lidar equation constrained with aerosol optical depths AODs derived by applying the Synergized Optical Depth of Aerosols SODA algorithm to ocean surface returns measured by CALIOP and CloudSats Cloud Profiling Radar. sigmaa and LR are retrieved for two independent scenarios that require somewhat different assumptions a a single homogeneous atmospheric layer 1L for which the LR is constant with height and b a vertically homogeneous layer with a constant LR overlying a marine boundary layer with a homogenous LR fixed at 25 sr two-layer method, 2L. These new retrievals differ from the standard CALIPSO version 4.1 V4 product, as the CALIOP-SODA method does not rely on an aerosol classification scheme to select LR. CALIOP-SODA sigmaa and LR are evaluated using airborne high-spectral-resolution lidar HSRL observations over the northwest Atlantic. CALIOP-SODA LR 1L and 2L positively correlates with its HSRL counterpart linear correlation coefficient r 0.67, with a negative bias smaller than 17.4 and a good agreement for sigmaa r 0.78 with a small negative bias vertical bar - 9.2 vertical bar. Furthermore, a global comparison of optical depths derived by CALIOP-SODA and CALIPSO V4 reveals substantial discrepancies over regions dominated by dust and smoke 0.24, whereas Aquas Moderate resolution Imaging Spectroradiometer MODIS and SODA AOD regional differences are within 0.06.