Determination of the instantaneous aerosol-radiation interactions (direct effects) using High Spectral Resolution Lidar (HSRL)-derived aerosol type-specific optical properties and CATCH algorithm

BETHANY SUTHERLAND, Nicholas Meskhidze, NC State University

     Abstract Number: 231
     Working Group: Aerosols, Clouds and Climate

Abstract
As aerosols remain the largest source of uncertainty in climate projections, utilizing aerosol type-specific values for the single scattering albedo (SSA) and asymmetry parameter (g) along with vertically-resolved HSRL retrievals of aerosol types (i.e. smoke, urban, dust, marine, etc.) presents a promising opportunity to lower uncertainty in aerosol-radiation interactions. The Creating Aerosol Types from Chemistry (CATCH) algorithm has been shown to produce aerosol types analogous to HSRL-retrieved types based on GEOS-Chem simulated aerosol microphysics over the North American domain during the SABOR and DISCOVER-AQ campaign periods (Dawson et al., 2017). It was also shown that average (effective) values of CATCH-derived SSA and g are generally characteristic for a given type and the variabilities in calculated type-specific values of SSA and g are within the range reported in the literature. As spatiotemporal distributions of HSRL-retrieved aerosol types are not currently available, the CATCH-derived types are used to calculate TOA radiative fluxes over the North American domain during the two campaigns. Radiative transfer calculations are performed using the RRTMG radiative transfer model, which has been implemented online in GEOS-Chem. To assess the uncertainty in the estimated direct effects due to implementing type-specific aerosol optical properties, TOA radiative fluxes with type-specific values of SSA and g as inputs in RRTMG are compared to fluxes calculated using the GEOS-Chem simulations for the same period. To estimate the uncertainty in prescribed SSA and g values for given aerosol types over the entire North American domain, the derived ranges in type-specific values for SSA and g are compared with AERONET-retrieved SSA and g on days when vertical profiles were dominated by a single aerosol type.