The Marine Stratus/Stratocumulus Experiment (MASE): Aerosol-cloud relationships in marine stratocumulus
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Authors
Lu, Miao-Lu
Conant, WIlliam C.
Jonsson, Haflidi H.
Varutbangkul, Varuntida
Flagan, Richard C.
Seinfeld, John H.
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Date of Issue
2007
Date
2007
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Abstract
The Marine Stratus/Stratocumulus Experiment (MASE) field campaign was
undertaken in July 2005 off the coast of Monterey, California to evaluate aerosol-cloud
relationships in the climatically important regime of eastern Pacific marine stratocumulus.
Aerosol and cloud properties were measured onboard the Center for Interdisciplinary
Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. One cloud that was
clearly impacted by ship emissions as well as the ensemble of clouds observed over the
entire mission are analyzed in detail. Results at both the individual and ensemble scales
clearly confirm the Twomey effect (first indirect effect of aerosols) and demonstrate
drizzle suppression at elevated aerosol number concentration. For the ship track impacted
cloud, suppressed drizzle in the track led to a larger cloud liquid water path (LWP) at the
same cloud thickness, in accord with the so-called second indirect effect. Ensemble
averages over all clouds sampled over the entire 13-flight mission show the opposite effect
of aerosol number concentration on LWP, presumably the result of other dynamic
influences (e.g., updraft velocity and ambient sounding profile). Individual polluted clouds
were found to exhibit a narrower cloud drop spectral width in accord with theoretical
prediction (M.-L. Lu and J. H. Seinfeld, Effect of aerosol number concentration on cloud
droplet dispersion: A large-eddy simulation study and implications for aerosol indirect
forcing, Journal of Geophysical Research, 2006). This field experiment demonstrates both
the indirect aerosol effect on ship track perturbed clouds, as well as the subtleties involved
in extracting these effects over an ensemble of clouds sampled over a 1-month period.
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Journal of Geophysical Research, Vol. 112, D10209
The article of record as published may be located at http://dx.doi.org/10.1029/2006JD007985.
The article of record as published may be located at http://dx.doi.org/10.1029/2006JD007985.
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Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS)
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.