The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission has now been orbiting the Earth for over 12 years, delivering high resolution, altitude-resolved profiles of the backscatter and extinction coefficients of clouds and aerosols on a near-continuous basis. Recently, several publications (e.g., Kim et al., 2017; Thorsen et al., 2017; Toth et al., 2018; Watson-Parris et al., 2018) have highlighted the fact that CALIOP does not detect all of the aerosol known to be present in the atmosphere, thus leading to underestimates of column aerosol optical depths (AOD) and direct aerosol radiative effects (DARE). Furthermore, these deficiencies were not significantly alleviated by the substantial improvements made in the recently release CALIOP version 4 data products. In response, the CALIPSO project has embarked on a major effort to retrieve the extinction coefficients from this here-to-fore ‘absent without leave’ (AWOL) aerosol. A first critical step in this effort is to implement additional constraints in the extinction retrieval process. This presentation describes the theory and implementation of one type of previously unused constraint: AOD estimates derived from CALIPSO lidar measurements of the ocean surface, as described in Venkata and Reagan, 2016. We will briefly review the underlying theory, discuss our preliminary findings, explore the accuracies required of the ancillary data products necessary for the retrievals, and show comparisons to other retrievals of AOD and extinction coefficients.
References
Kim, M.-H. et al., 2017: Quantifying the low bias of CALIPSO’s column aerosol optical depth due to undetected aerosol layers, J. Geophys. Res. Atmos., 122, 1098–1113, doi:10.1002/2016JD025797.
Thorsen, T. J. et al., 2017: The impact of lidar detection sensitivity on assessing aerosol direct radiative effects, Geophys. Res. Lett., 44, 9059–9067, doi:10.1002/2017GL074521.
Toth, T. D. et al., 2018: Minimum Aerosol Layer Detection Sensitivities and their Subsequent Impacts on Aerosol Optical Thickness Retrievals in CALIPSO Level 2 Data Products, Atmos. Meas. Tech., 11, 499–514, doi:10.5194/amt-11-499-2018.
Venkata and Reagan, 2016: Aerosol Retrievals from CALIPSO Lidar Ocean Surface Returns, Remote Sens., 8, 1006, doi:10.3390/rs8121006.
Watson-Parris et al., 2018: On the limits of CALIOP for constraining modelled free-tropospheric aerosol, Geophys. Res. Lett., in review.
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