Cloud liquid water path at the North Slope of Alaska has minimal sensitivity to local meteorology in Arctic winter

Source abstract

Mixed-phase clouds in the Arctic are tightly coupled to the surface energy budget in the cold months, helping to set surface temperatures and sea ice extent. However, the meteorological conditions that give rise to these clouds and their remarkable persistence across the Arctic are not well constrained, leading to model biases. Using over a decade of observations from the North Slope of Alaska, this research investigates the relationships between cloud base temperature and moisture, bulk atmospheric moisture, wind direction, large-scale circulation, and cloud liquid and ice water path. Liquid-containing clouds are ubiquitous at this site, occurring 60 %–70 % of the time between November and March, although about one-third of those cases have a liquid water path under 10 g m −2 . We find that liquid water path is weakly sensitive to temperature and moisture and remarkably insensitive to wind direction and large-scale circulation. Furthermore, meteorological regimes with significant differences in temperature, moisture, and cloud fraction do not produce appreciable differences in cloud liquid water path. Ice water path, on the other hand, is clearly correlated with bulk atmospheric moisture, with particularly strong increases when precipitable water vapor exceeds the 90th percentile, and may be responsible for the muted response of liquid water path to high atmospheric moisture. To explain the observed sensitivity of ice water path and relative insensitivity of liquid water path to meteorology and large-scale circulation, we propose a series of hypotheses centered around a lack of dissipative mechanisms and the role of ice in enabling or limiting liquid mass accumulation.