Tuesday, 13 January 2009
Large scale variability in the Arctic cloud and radiative climatology
Hall 5 (Phoenix Convention Center)
Recent changes in the Arctic (e.g. increases surface and atmospheric temperatures, decreases in sea-ice extent) coincide with increases in atmospheric greenhouse gases concentrations, suggesting the Arctic region is sensitive to anthropogenic forcing. In addition, feedbacks mechanisms in the Arctic may be enhancing climate change. These feedbacks include processes associated with temperature change, sea ice, albedo, advection, cloud/radiative effects, and atmospheric modes. The North Atlantic Oscillation (NAO)/Northern Annular Mode (NAM is a well-known atmospheric oscillation with associated atmospheric anomalies. However, how the modes affect and possibly feedback with the Arctic cloud/radiative and surface temperature anomalies is not yet fully understood. This study examines large-scale variability in Arctic clouds and radiative properties. This variability is related to the well known Northern Hemispheric atmospheric variability (e.g., NAO/NAM). We show that differences in longwave cloud radiative forcing are near 20 W m-2 between a positive NAM winter and a negative NAM winter. This difference occurs in and around Northern Europe (30W to 60E, poleward of 60N). Over Greenland the difference between NAM Positive minus NAM Negative longwave cloud radiative forcing are negative. This dipole structure is typical in NAM studies. Possible connections between the radiative forcing, dynamics, and surface temperature are explored.