Dynamical and microphysical characteristics and interactions in Arctic mixed-phase clouds

Arctic mixed-phase clouds play a key role in Arctic climate through their persistent nature, variability of phase composition, and frequent precipitation. Many of the key mechanisms that characterize these clouds are poorly understood due to the complexities associated with a three-phase water system, the complex interactions with aerosols, and a general dearth of observational history. A number of past experiments have provided insights into these clouds in many different conditions, including coastal fall observations during the Mixed-Phase Arctic Clouds Experiment (MPACE) in 2004, coastal spring observations during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in 2008, and summer observations over the sea-ice during the Arctic Summer Cloud Ocean Study (ASCOS) in 2008. In spite of the unique environments encountered during each of these campaigns, the mixed-phase stratocumulus clouds maintain a qualitatively similar structure of supercooled liquid water, formed via cloud-scale circulations, from which ice crystals form and fall. Thus, these different observational perspectives provide important insight into why Arctic mixed-phase stratocumulus are so persistent in spite of differing forcing mechanisms and frequent mass loss through precipitation.

Many aspects of Arctic mixed-phase stratocumulus are explored in this presentation in order to build a better understanding of their remarkable persistence. In particular, measurements from active and passive, ground-based remote sensors are combined to characterize these clouds in terms of their phase partitioning, microphysical, macrophysical and dynamical properties. In some cases this information will be considered within the context of measurements of atmospheric thermodynamic stability to further characterize the interactions between the cloud and surface. Lastly, seasonal impacts on the cloud layers and their interaction with the surface and free-troposphere will be discussed.