Toward an Explanation of the Annual Cycle of Cloudiness over the Arctic Ocean

Abstract

Abstract The annual cycle of low cloud amount over the Arctic Ocean is examined using climatological data and a radiative-turbulent column model. Three hypotheses for the annual cycle are formulated, compared with climatological data for consistency, and then tested using the numerical model. The hypotheses identify three factors that might explain the difference in arctic low cloud amount between summer and winter: 1) the difference in surface specific humidity between the pack ice and the surrounding continents, 2) evaporation at the surface of the ice pack, and 3) the temperature-dependent formation and precipitation of atmospheric ice. Qualitatively, the hypotheses all appear to be consistent with available climatological data, except that the transition between the winter and summer cloudiness regimes occurs one month before the influx of atmospheric moisture increases from its wintertime level, which is inconsistent with the first hypothesis. The model, which includes a turbulence-closure cloud sche...