The Influence of Elevated Smoke Layers on Stratocumulus Clouds over the SE Atlantic - 2

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By Sampa Das1, H. Harshvardhan2, Peter Colarco1

1. NASA Goddard Space Flight Center 2. Purdue University

Data associated with the publication "Influence of Elevated Smoke Layers on Stratocumulus Clouds over the SE Atlantic in the NASA Goddard Earth Observing System (GEOS) Model"

Version 1.0 - published on 09 Jan 2020 doi:10.4231/QB5V-DF73 - cite this Content may change until committed to the archive on 09 Feb 2020

Licensed under CC0 1.0 Universal

Description

This dataset contains output thermodynamic variables from three model experiments:

CTL: Control case, in which the GEOS model was prescribed with MERRAero (aerosol reanalysis product) aerosol mass mixing ratios.
RED: Redistributed aerosol case, in which aerosol vertical profiles were adjusted based on CALIOP Lidar climatology.
NOA: No Aerosol case, in which smoke aerosols were removed from over the redistribution domain.

This dataset is one part of a two-part series. Access the entire series here.

Previous evaluations of simulated aerosol transport over the South-east Atlantic by global aerosol models, including Goddard Earth Observing System (GEOS) Atmospheric GCM, showed that the bulk of the modeled smoke aerosol layer resided ~1-2 km lower than CALIOP lidar observations over the ocean. Using this finding as the motivation, this study examines the changes in model simulated cloud properties in response to redistributing the aerosol profiles over the ocean. Ten years (2006-15) of CALIOP retrieved smoke aerosol extinction profiles were used to redistribute the model simulated aerosol mass on a monthly mean basis, keeping the column aerosol mass conserved. The results from the model sensitivity experiments show that elevating the aerosol layer to higher levels in agreement with the observations causes an increase in cloud fractions by ~33% for shallow marine boundary layers (MBL), while cloud fractions decrease by ~30% for deeper MBL. We found that aerosol-induced warming within the shallow MBL cloud layers leads to reduced cloud presence due to decrease in relative humidity at these levels. For deeper MBL, increased MBL stability in the lower altitude aerosol case compared to the elevated aerosol layer case suppresses the cloud vertical extent, enhances the cloud cover and delays the stratocumulus to cumulus transition. Finally, aerosol redistribution impacts on radiative forcing are investigated, which appear to be mainly driven by the changes in cloud area fractions rather than in-cloud LWP changes between the model experiments.

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