Aerosol Impacts on the Diurnal Cycle of Marine Stratocumulus
Open Access
- 1 August 2008
- journal article
- Published by American Meteorological Society in Journal of the Atmospheric Sciences
- Vol. 65 (8), 2705-2718
- https://doi.org/10.1175/2008jas2451.1
Abstract
Recent large-eddy simulation (LES) studies of the impact of aerosol on the dynamics of nocturnal marine stratocumulus revealed that, depending on the large-scale forcings, an aerosol-induced increase of the droplet concentration can lead to either an increase or a decrease of the liquid water path, hence contrasting with the cloud thickening that is expected from a reduction of the precipitation efficiency. In this study, the aerosol impacts on cloud microphysics are examined in the context of the boundary-layer diurnal cycle using 36-h LES simulations of pristine and polluted clouds. These simulations corroborate previous findings that during nighttime aerosol-induced liquid water path changes are sensitive to the large-scale forcings via enhancement of cloud-top entrainment such that, ultimately, the liquid water path may be reduced when the free-tropospheric-entrained air is drier. During the day, however, enhanced entrainment, inhibition of drizzle evaporation below cloud base, and reduced sensible heat flux from the surface lead to a more pronounced decoupling of the boundary layer, which significantly amplifies the liquid water path reduction of the polluted clouds. At night the sign of the liquid water path difference between pristine and polluted clouds depends upon large-scale forcings, while during the day the liquid water path of polluted clouds is always smaller than the one of the pristine clouds. Suggestions are made on how observational studies could be designed for validation of these simulations.Keywords
This publication has 56 references indexed in Scilit:
- The Three-Dimensional Structure and Kinematics of Drizzling StratocumulusMonthly Weather Review, 2007
- Cloud droplet sedimentation, entrainment efficiency, and subtropical stratocumulus albedoGeophysical Research Letters, 2007
- Observations of the Structure of Heavily Precipitating Marine StratocumulusJournal of the Atmospheric Sciences, 2005
- Cloud microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climateJournal of Geophysical Research: Atmospheres, 2003
- An observational study of drizzle formation in stratocumulus clouds for general circulation model (GCM) parameterizationsJournal of Geophysical Research: Atmospheres, 2003
- Enhancement of cloud cover and suppression of nocturnal drizzle in stratocumulus polluted by hazeGeophysical Research Letters, 2003
- Simulations of aerosol‐cloud‐dynamical feedbacks resulting from entrainment of aerosol into the marine boundary layer during the Atlantic Stratocumulus Transition ExperimentJournal of Geophysical Research: Atmospheres, 2002
- On the parameterization of activation spectra from cloud condensation nuclei microphysical propertiesJournal of Geophysical Research: Atmospheres, 2000
- Measurements of ship‐induced tracks in clouds off the Washington coastJournal of Geophysical Research: Atmospheres, 1998
- The Relation of Air Mass Structure to the Field of Motion over the Eastern North Pacific Ocean in SummerTellus, 1960