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Published July 16, 2008 | Published + Supplemental Material
Journal Article Open

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)


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.

Additional Information

© 2008 American Geophysical Union. Received 21 August 2007; revised 31 December 2007; accepted 25 February 2008; published 3 July 2008. The field experiment would not have been possible without the efforts of numerous instrument operators and the CIRPAS pilots and crew (M. Hubbell, Chris McGuire, and Roy Woods). A. Shelby Frisch helped with analysis of the vertical velocity data. Owen Cooper and Christoph Senff are thanked for their flight planning support. The excellent logistical support by Gerhard Hubler (NOAA), Cathy Burgdorf (NOAA) and Shelley Baccus (NASA) is gratefully acknowledged. H.J. and G.F. were funded by NOAA's Climate Goal. Flight operations and the participation of the California Institute of Technology group were supported by NOAA grant NA06OAR4310082.

Attached Files

Published - 268-Jiang-2008.pdf

Supplemental Material - jgrd14353-sup-0001-t01.txt

Supplemental Material - jgrd14353-sup-0002-t02.txt

Supplemental Material - jgrd14353-sup-0003-t03.txt

Supplemental Material - jgrd14353-sup-0004-t04.txt


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August 22, 2023
October 23, 2023