Cumulus Cloud and Drizzle Microphysics Relationships With Complete CCN Spectra
James G. Hudson, Stephen Noble
Abstract
Abstract Comparisons of high‐resolution extended range CCN spectra measured at 100 m altitude with cloud and drizzle microphysics in the Rain in Cumulus over the Ocean (RICO) aircraft field project are presented. CCN concentrations, N CCN , active at supersaturations, S , >0.1% showed positive relationships with cloud droplet concentrations, N c , measured at intermediate (606–976 m) and very high altitudes (1,763–3,699 m). These correlation coefficients, R , progressively increased with S while the two‐tailed probabilities, P2, progressively decreased with S to < 10 −6 at 1.6%S. More important were the positive relationships between N CCN active at S < 0.1% and drizzle drop concentrations, N d , at high (977–1,662 m), very high and high‐very high altitudes combined (977–3,699 m). All of these relationships were consistent for eight different cloud liquid water content, L c , thresholds (for N c ) and L c bins (for N d ) ranging from 0.0002 to 0.3 g/m 3 . Negative relationships between CCN modality and low altitude (76–475 m) cloudiness coupled with no relationship of N CCN active at any S with N c of these low clouds indicated a cloud effect on ambient aerosol. This is a demonstration of clouds causing bimodal aerosol.