Low‐altitude summer/winter microphysics, dynamics, and CCN spectra of northeastern Caribbean small cumuli, and comparisons with stratus

Abstract

Low-altitude cloud microphysics and cloud condensation nuclei (CCN) spectra are presented and analyzed from two cumulus cloud aircraft field campaigns, Ice in Clouds Experiment-Tropical (ICE-T) and Rain in Cumulus over the Ocean (RICO), in the same eastern Caribbean location at opposite seasons. These are further compared with two previously analyzed stratus cloud aircraft campaigns off the central California coast, Physics of Stratocumulus Tops (POST) and Marine Stratus/Stratocumulus Experiment (MASE). Multiple regression analysis predictions of cloud droplet concentrations (N c ) based on CCN spectra, N CCN (S) where S is supersaturation, compared much better with measured N c than single N CCN -N c regressions in both cumulus projects. The addition of vertical velocity (W) to the single and multiple regressions showed small improvements. For RICO the multiple regression correlations were also superior to previous adiabatic model predictions of N c also based on N CCN (S) and mean W. More adiabatic cloud parcels with considerably higher N c , liquid water contents, and W showed only slightly better correlations than flight-averaged N c of all low clouds. Results show the value of more extensive CCN spectra and the relative unimportance of W variations for determining N c , in these Caribbean cumuli. The fact that flight-averaged N c of all low cloud data was almost as well correlated with N CCN (S) as were N c of more adiabatic cloud parcels indicates that entrainment did not significantly perturb CCN-N c relationships. As should be expected higher cloud S were determined for the cumulus clouds than for the stratus clouds. Suppression of cloud S by higher N CCN that had previously been observed in stratus was observed in ICE-T but not in RICO where the N CCN range may have been too low for cloud S suppression. But ICE-T and POST even showed this S suppression over the same limited N CCN range as RICO (< 200 cm À3 ).

CCN Spectral Shape and Stratus Cloud and Drizzle Microphysics

“…The influences on cloud and drizzle microphysics noted here are similar to the effects of higher CCN concentrations, N CCN , that is, mainly anthropogenic CCN that cause IAE (e.g., Hudson & Li, 1995;Hudson & Svensson, 1995;Hudson & Yum, 2001;Yum & Hudson, 2001b;Yum & Hudson, 2002Hudson & Mishra, 2007;HN14a;Hudson & Noble, 2014b). The difference is that the results presented here consider CCN spectral shape not N CCN at any specific S. This accounts for the variability of S eff caused by N CCN and σ w variations.…”

“…This is especially demonstrable for cases without an LWC c cloud threshold. Further along this line, Hudson and Noble () showed that cloud subadiabaticity minimally disrupted ICE‐T N CCN ‐ N c relationships in cumulus clouds where entrainment generally has a greater impact on cloud microphysics than is the case for stratus clouds such as MASE. H15 noted that the variability of N CCN and N c among the MASE flights could not be tied to the minimal air mass trajectory variability that was observed.…”

Cloud supersaturations from CCN spectra Hoppel minima

“…Here we present high‐resolution CCN spectra from two of the most recent projects. MASE was done in polluted stratus clouds off the central California coast in July 2005 [ Hudson , ; Wang et al ., ; Hudson and Noble , , hereafter HN14a; Hudson and Noble , , hereafter HN14b]. The CCN and cloud microphysics measurements during MASE are described in HN14a.…”

Aircraft measurements of the vertical distribution and activation property of aerosol particles over the Loess Plateau in China

“…Therefore, another difficulty encountered in aerosol research is the relationship between aerosol particles and cloud droplets. Researches including observations near the ground and many extensive aircraft measurements have focused on the activation properties of aerosols and CCN (Junge and McLaren, 1971;Fitzgerald, 1973;Hudson and Yum, 2001;Hudson, 2002, 2004;Frank et al, 2006;Dusek et al, 2006;Hudson and Mishra, 2007;Kuwata et al, 2008;Hudson et al, , 2010Hudson et al, , 2012, 2014a, 2014bDeng et al, 2011Deng et al, , 2013.…”