Lu, Miao-Ling and Wang, Jian and Freedman, Andrew and Jonsson, Haflidi H. and Flagan, Richard C. and McClatchey, Robert A. and Seinfeld, John H. (2003) Analysis of Humidity Halos around Trade Wind Cumulus Clouds. Journal of the Atmospheric Sciences, 60 (8). pp. 1041-1059. ISSN 0022-4928 http://resolver.caltech.edu/CaltechAUTHORS:LUMjas03
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Regions of enhanced humidity in the vicinity of cumulus clouds, so-called cloud halos, reflect features of cloud evolution, exert radiative effects, and may serve as a locus for new particle formation. Reported here are the results of an aircraft sampling campaign carried out near Oahu, Hawaii, from 31 July through 10 August 2001, aimed at characterizing the properties of trade wind cumulus cloud halos. An Aerodyne Research, Inc., fast spectroscopic water vapor sensor, flown for the first time in this campaign, allowed characterization of humidity properties at 10-m spatial resolution. Statistical properties of 60 traverses through cloud halos over the campaign were in general agreement with measurements reported by Perry and Hobbs. One particularly long-lived cloud is analyzed in detail, through both airborne measurement and numerical simulation, to track evolution of the cloud halos over the cloud's lifetime. Results of both observation and the simulation show that cloud halos tend to be broad at lower levels and narrow at upper levels, and broader on the downshear side than on the upshear side, broadening with time particularly in the downshear direction. The high correlation of clear-air turbulence distribution with the halo distribution temporally and spatially suggests that the halo forms, in part, due to turbulent mixing at the cloud boundary. Radiative calculations carried out on the simulated cloud and halo field indicate that the halo radiative effect is largest near cloud top during mature and dissipation stages. The halo-enhanced atmospheric shortwave absorption, averaged over this period, is about 1.3% of total solar absorption in the column.
|Additional Information:||© 2006 American Meteorological Society Manuscript received June 17, 2002, in final form November 12, 2002 This work was supported by National Science Foundation Grants ATM-9907010 and ATM-9910744. This work was also supported in part by the Office of Naval Research. The authors wish to acknowledge Dr. William C. Conant for helpful comments. We also thank anonymous reviewers for their valuable comments on this work.|
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|Deposited On:||17 Nov 2006|
|Last Modified:||26 Dec 2012 09:17|
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