Radiative and Microphysical Properties of Autumnal Arctic Clouds

Clouds strongly modulate the surface energy budget over the Arctic ice pack. In autumn, as the amount of insolation rapidly decreases, their main influence is felt through enhancing the emissivity of the cold dry atmosphere. During autumn, low clouds are present over the arctic ice pack nearly 60% of the time. In addition, ice clouds, which are not included in this statistic, become increasingly common as autumn progresses. The microphysical properties of these clouds, which determine their radiative impact, are not well known due to the dearth of observations. A main objective of the Beaufort and Arctic Storms Experiment (BASE) was to document and understand the transition in cloud properties over the Arctic ice pack in autumn from predominantly liquid to crystalline.