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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L16804, doi:10.1029/2007GL030044, 2007

Relationships between CCN and cloud microphysics variations in clean maritime air

James G. Hudson

Desert Research Institute, Nevada System of Higher Education, Reno, Nevada, USA

Subhashree Mishra

Desert Research Institute, Nevada System of Higher Education, Reno, Nevada, USA

Abstract

Flight-averaged CCN concentrations during the Rain in Cumulus over the Ocean (RICO) field project varied by a factor of four. This was sufficient to provide correlations with flight-averaged total cloud droplet concentrations (N_c) and mean diameters (MD) that showed greater influence of CCN than updraft velocity (w) on N_c and especially MD. The product of CCN and w produced even stronger correlations with N_c and MD. An earlier RICO study had shown an inverse relationship of N_c and giant nuclei (GN) with large cloud droplet concentrations (N_LD). These two RICO studies now show that the aerosol with the most influence on N_LD (MD) is CCN. The results of the present study are similar to earlier studies in more polluted clouds that also showed more influence of CCN than GN on MD/N_LD/drizzle. The present study indicates that variations in CCN concentrations even within maritime air masses modulate precipitation.

Received 15 March 2007; accepted 19 July 2007; published 17 August 2007.

Keywords: CCN; aerosol; drizzle.

Index Terms: 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry.

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Citation: Hudson, J. G., and S. Mishra (2007), Relationships between CCN and cloud microphysics variations in clean maritime air, Geophys. Res. Lett., 34, L16804, doi:10.1029/2007GL030044.

Copyright 2007 by the American Geophysical Union.