Cloud Base Cloud Condensation Nuclei Measurements in Summertime North Dakota

A major uncertainty on the prediction of future climates is exactly how clouds affect climate, however, it is not completely understood. Cloud based droplet properties in developing cumulus clouds are related to cloud condensation nuclei (CCN) concentration, which can vary greatly from location to location and atmospheric conditions. However, most cloud models and parameterizations rely on a few observations taken in a few locations to determine CCN properties and hence cloud droplet properties. To better understand and represent cloud processes within climate models, more detailed measurements and observations need to be made. During the 2008, 2010, and 2012 Polarimetric Cloud Analysis and Seeding Test (POLCAST) field campaigns, airborne CCN measurements were made in Eastern North Dakota. Airborne measurements were made right below developing cumulus clouds during the months of June and July. During the 2012 field campaign, both Droplet Measurements Technologies (DMT) and University of Wyoming (UWyo) CCN counters were used for airborne measurements. The DMT CCN counters measured at three different ambient supersaturations of 0.2%, 0.3%, and 0.6%. The UWyo CCN counters measured at a constant supersaturation of 0.6%. The DMT 0.6% supersaturation CCN concentrations measurements were systematically higher than the UWyo 0.6% supersaturation measurements. A large daily variation in CCN concentrations is seen across the field campaign.