Statistical comparison of properties of simulated and observed cumulus clouds in the vicinity of Houston during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)

Author
Jiang, Hongli
Feingold, Graham
Jonsson, Haflidi H.
Lu, Miao-Ling
Chuang, Patrick Y.
Flagan, Richard C.
Seinfeld, John H.
Date
2008Metadata
Show full item recordAbstract
We present statistical comparisons of properties of clouds generated by Large Eddy
Simulations (LES) with aircraft observations of nonprecipitating, warm cumulus
clouds made in the vicinity of Houston, TX during the Gulf of Mexico Atmospheric
Composition and Climate Study (GoMACCS), carried out in the summer of 2006. Aircraft
data were sampled with the Center for Interdisciplinary Remotely Piloted Aircraft Studies
(CIRPAS) Twin Otter airplane. Five flights (days) that are most suitable for studying
aerosol-cloud interactions are selected from the 22 flights. The model simulations are
initiated with observed environmental profiles. The simulations are used to generate an
ensemble of thousands of cumulus clouds for statistically meaningful evaluations.
Statistical comparisons focus on the properties of a set of dynamical and thermodynamical
variables, sampled either in the cloud or the cloud updraft core. The set of variables
includes cloud liquid water content (LWC), number mixing ratio of cloud droplets (Nd),
cloud effective radius (re), updraft velocity (w), and the distribution of cloud sizes. In
general, good agreement between the simulated and observed clouds is achieved in the
normalized frequency distribution functions, the profiles averaged over the cloudy
regions, the cross-cloud averages, and the cloud size distributions, despite big differences
in sample size between the model output and the aircraft data. Some unresolved
differences in frequency distributions of w and possible differences in cloud fraction are
noted. These comparisons suggest that the LES is able to successfully generate the
cumulus cloud populations that were present during GoMACCS. The extent to which this
is true will depend on the specific application.
Description
Journal of Geophysical Research, Vol. 113, D13205
The article of record as published may be located at http://dx.doi.org/10.1029/2007JD009304.
Rights
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.Collections
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