Statistical analysis of microphysical properties and the parameterization of effective radius of warm clouds in Beijing area

In this paper warm cloud microphysical parameters including cloud droplet number concentration (N-c), liquid water content (q(l)) and effective radius (r(e)) from 75 flights around the Beijing area during 2005 and 2006 are summarized. Average N-c (cm(-3)) for Cu, Sc, Ac, As and Ns are 376 +/- 290, 257 +/- 226,147 +/- 112, 60 +/- 35 and 60 +/- 84, respectively. Many records of high N-c above 1000 cm(-3) are observed. The large standard deviations indicate a large variation of N-c and q(l) in this region. The maxima of q(l) reach 1.4 g m(-3) in Cu and 1.0 g m(-3) in Sc, respectively. Different parameterizations of effective radius are examined with the in-situ data in this area. There are different ways to obtain the prefactor representing the relationship between effective radius and mean volume radius. Significant systematic errors are found to be at the large sizes when the prefactor is expressed with relative dispersion under the Gamma Distribution. Fixed prefactor of 1, which was widely used, even produces much larger error. A prefactor of 1.22 is found to be better than the former two methods by fitting with the observed data. The effective radius is further parameterized as functions of mean volume radius, liquid water content and cloud droplet number concentration. We suggest that the effective radius can be parameterized as r(e,p) approximate to 1.20r(v) + 0.22-1.28/r(v)(2), which is a practical and more accurate scheme without too much computation complexity. (C) 2009 Elsevier B.V. All rights reserved.