Cloud Microphysical Properties of Summertime Arctic Stratocumulus during the ACLOUD Campaign: Comparison with Previous Results in the European Arctic

The Arctic region is more sensitive to climate change than any other region of the Earth (Solomon et al., 2007). Clouds and particularly low-level clouds related processes have a major impact on the Arctic surface energy budget (Curry, 1995; Curry et al., 1996; Morrison et al., 2011). Observations suggest that boundary layer mixed phase clouds (MPC, mixture of liquid droplets and ice) are ubiquitous in the Arctic and persist for several days under a variety of meteorological conditions (Mioche et al., 2015; Morrison et al., 2012; Shupe et al., 2011; Shupe and Intrieri, 2004). They occur as single or multiple stratiform layers of supercooled droplets near the cloud top from which ice crystals form and precipitate (Mioche et al., 2017). These clouds have a large impact on the surface radiative fluxes and Arctic climate feedbacks (Kay et al., 2012; Kay and Gettelman, 2009) but are often poorly predicted by models (Forbes and Ahlgrimm 2014). In particular, a correct representation of the MPC microphysical properties in numerical models is needed for both weather forecasts and climate prediction (Barret et al., 2017a,b).

In May-June 2017, a suite of “in situ” microphysical probes was deployed onboard the AWI Polar 6 aircraft during the ACLOUD experiment in the Svalbard region (Arctic Cloud Observations Using airborne measurements during polar Day). ACLOUD is a joint project of different German universities and research institutes embedded in the Transregional collaborative research centre (AC)3. The general goal of ACLOUD is to gather a comprehensive data set of what will contribute to a process level understanding of clouds in the Arctic and their role in the amplified climate change observed in this region.

This campaign gave us the opportunity to explore the microphysical properties of summer arctic stratocumulus clouds over different surface conditions (open sea, sea ice and marginal sea ice zone). Cloud vertical profiles of liquid and ice water content, number concentration and effective size will be presented over different surface conditions. A special focus will be put on the the data processing procedure methodology to discriminate ice crystals from water droplets from the in situ probes : CDP, CIP/PIP and SID3. First results show the presence of higher liquid water content associated with larger droplets than what was measured in spring clouds (Mioche et al., 2017). Besides, relatively high ice particle concentrations were found in some ACLOUD cloud vertical profiles.

These results will be compared to the studies from Lloyd et al. 2015 perfomed during the ACCACIA campaign (summer/spring cloud over open sea), Young et al. 2016 (spring cloud transition from sea ice to open sea) and the cloud vertical profiles established by Mioche et al. 2017 over the Greenland and Barents seas.