| Summary: | Thesis (Ph.D.)--University of Washington, 2021 The clear-sky aerosol direct radiative effect was estimated at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in Lamont, Oklahoma and Tropical Western Pacific (TWP) site in Darwin, Australia. The NASA Langley Fu-Liou radiative transfer (RT) model was used with observed inputs including aerosol vertical extinction profile from the Raman lidar (RL); spectral aerosol optical depth (AOD), single-scattering albedo and asymmetry factor from Aerosol Robotic Network (AERONET); temperature and water vapor profiles from radiosondes; and surface shortwave spectral albedo from radiometers. A radiative closure experiment was conducted for clear-sky conditions. The mean differences of modeled and observed surface downwelling shortwave total fluxes were 1 W m−2 at SGP and 2 W m−2 at TWP, which are within observational uncertainty. At SGP, the estimated annual mean clear-sky aerosol DRE is -3.00±0.58 W m−2 at the top of atmosphere (TOA) and -6.85±1.00 W m−2 at the surface. The strongest aerosol DRE of -4.81 (-10.77) W m−2 at the TOA (surface) are in the summer when AODs are largest. The weakest aerosol DRE of -1.28 (-2.77) W m−2 at the TOA (surface) are in November-January when AODs and single-scattering albedos are lowest. At TWP, the annual mean clear-sky DRE is -2.82 W m−2 at the TOA and -10.34 W m−2 at the surface. The strongest aerosol DRE of -5.95 (-22.20) W m−2 at the TOA (surface) are in November (October) due to the biomass burning season’s peak. The weakest aerosol DRE of -0.96 (-4.16) W m−2 at the TOA (surface) are in March (April) when AODs are smallest. The all-sky aerosol DRE was also estimated for the first time at the SGP site. To estimate the aerosol DRE under all-skies, the observations used to estimate the clear-sky aerosol DRE were supplemented with cloud vertical extinction profile from the RL and cloud water content profiles from the Ka-band Zenith ARM radar (KAZR) and the millimeter cloud radar (MMCR). A radiative closure ...
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