ARCTIC CLOUD FORCING DETERMINED BY LIDAR CLOUD MEASUREMENTS AND BROADBAND SURFACE RADIOMETERS

摘要

Lidar measurements obtained over the Arctic Ocean for a one year period, along with radiometers and atmospheric temperature soundings, revealed previously undocumented properties of Arctic clouds and their radiative impact on the sea ice surface over an annual cycle. The lidar cloud observations revealed the predominance of liquid water clouds in all seasons throughout the polar year and the strong radiative effect clouds in liquid phase impart onto the surface. Lidar measurements were also used to characterize diamond dust. These observations showed that diamond dust, over the Western Arctic Ocean region, had a much lesser effect on the surface radiation than previously believed and modeled. When compared to surface observer log notes the lidar data showed that surface observers had incorrectly coded diamond dust events ～ 45% of the time. These miscoded events occurred almost exclusively under conditions with poor illumination (December through March). In 95% of the miscoded diamond dust events, lidar revealed the presence of thin liquid water clouds precipitating ice crystals down to the surface. In general, lidar observations of clouds in liquid versus ice phase and their location in the atmosphere have proven to be a critical observation in the polar regions for understanding and modeling the surface heat budget.