Master's Defense: Roy Prouty
Monday, January 25, 2016 · 1 - 3:30 PM
Tittle: Impact
of Above-Cloud Aerosols on the Angular Distribution Pattern of Cloud
Bidirectional Reflectance and Implication for Above-Cloud Aerosol Direct
Radiative Effect
Abstract: Although
most aerosols are emitted into the atmospheric boundary layer, they can
be convectively lifted above low-level clouds, or in some cases are
emitted at altitudes higher than the boundary layer and are subsequently
transported over low-level cloud decks. In fact, above-cloud aerosols
(ACA) have been observed in several regions of the globe. ACA is an
important component of the climate system because its interactions
(scattering and absorption) with shortwave (SW) solar radiation
(so-called direct radiative effect) could differ substantially from that
of clear-sky aerosols or below cloud aerosols, particularly for
absorbing particles.
The objective of this research is to understand how ACA influences the bi-directional reflection distribution functions (BRDF) of otherwise clean clouds. In this study, the spectral BRDFs of polluted (ACA+low-level cloud) and unpolluted scenes (cloud only) are calculated and compared. We found the BRDFs of polluted and clean clouds are similar in the near-infrared spectral region where the ACA layer is not optically active. However large differences develop in the UV and visible regions, where the radiative effects of ACA are strong. Furthermore, we analyzed how the differences depend on sun-satellite view geometry and investigated the consequent implications for deriving the direct radiative effects of ACA from satellite observations.
The objective of this research is to understand how ACA influences the bi-directional reflection distribution functions (BRDF) of otherwise clean clouds. In this study, the spectral BRDFs of polluted (ACA+low-level cloud) and unpolluted scenes (cloud only) are calculated and compared. We found the BRDFs of polluted and clean clouds are similar in the near-infrared spectral region where the ACA layer is not optically active. However large differences develop in the UV and visible regions, where the radiative effects of ACA are strong. Furthermore, we analyzed how the differences depend on sun-satellite view geometry and investigated the consequent implications for deriving the direct radiative effects of ACA from satellite observations.