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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D24204, doi:10.1029/2007JD008536, 2007

A single-column model intercomparison of a heavily drizzling stratocumulus-topped boundary layer

Matthew C. Wyant

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Christopher S. Bretherton

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Andreas Chlond

Max Planck Institute for Meteorology, Hamburg, Germany


Brian M. Griffin

Department of Mathematical Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA


Hiroto Kitagawa

Japan Meteorological Agency, Tokyo, Japan


Cara-Lyn Lappen

Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA


Vincent E. Larson

Department of Mathematical Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA


Adrian Lock

Met Office, Exeter, UK


Sungsu Park

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Stephan R. de Roode

Koninklijk Nederlands Meteorologisch Instituut, De Bilt, Netherlands


Junya Uchida

Department of Applied Mathematics, University of Washington, Seattle, Washington, USA


Ming Zhao

NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA


Andrew S. Ackerman

NASA Goddard Institute for Space Studies, New York, New York, USA


Abstract

This study presents an intercomparison of single-column model simulations of a nocturnal heavily drizzling marine stratocumulus-topped boundary layer. Initial conditions and forcings are based on nocturnal flight observations off the coast of California during the DYCOMS-II field experiment. Differences in turbulent and microphysical parameterizations between models were isolated by slightly idealizing and standardizing the specification of surface and radiative fluxes. For most participating models, the case was run at both typical operational vertical resolution of about 100 m and also at high vertical resolution of about 10 m. As in prior stratocumulus intercomparisons, the simulations quickly develop considerable scatter in liquid water path (LWP) between models. However, the simulated dependence of cloud base drizzle fluxes on LWP in most models is broadly consistent with recent observations. Sensitivity tests with drizzle turned off show that drizzle substantially decreases LWP for many models. The sensitivity of entrainment rate to drizzle is more muted. Simulated LWP and entrainment are also sensitive to the inclusion of cloud droplet sedimentation. Many models underestimate the fraction of drizzle that evaporates below cloud base, which may distort the simulated feedbacks of drizzle on turbulence, entrainment, and LWP.

Received 12 February 2007; accepted 2 August 2007; published 27 December 2007.

Keywords: stratocumulus; single-column model; microphysics.

Index Terms: 3310 Atmospheric Processes: Clouds and cloud feedbacks; 3354 Atmospheric Processes: Precipitation (1854); 3307 Atmospheric Processes: Boundary layer processes; 3379 Atmospheric Processes: Turbulence (4490); 0545 Computational Geophysics: Modeling (4255).

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Citation: Wyant, M. C., et al. (2007), A single-column model intercomparison of a heavily drizzling stratocumulus-topped boundary layer, J. Geophys. Res., 112, D24204, doi:10.1029/2007JD008536.