Satellite Perspectives on the Role of Clouds and Precipitation in Arctic Energy Balance (Invited Presentation)

Observations from active sensors aboard polar orbiting satellites have yielded valuable new insights into the character and impacts of clouds and precipitation in polar regions.  Prior to these observations, evidence of the importance of super-cooled liquid containing clouds in the Arctic climate was limited to ground-based observations on local scales.  Recent analyses of CloudSat and CALIPSO datasets have confirmed the importance of these clouds in modulating surface properties across the entire Arctic.  This presentation will summarize recent efforts to quantify the radiative impacts of Arctic clouds and probe the elusive relationships between the presence of super-cooled liquid water, falling snow, and surface energy and mass balance poleward of 60°N.  It is found that emission from super-cooled liquid accounts for up to half of the enhanced downwelling longwave radiation from cloud cover over snow and ice covered surfaces.  Current climate models are found to significantly under-estimate the frequency of occurrence of super-cooled liquid in the Arctic and, in turn, under-estimate the surface warming.  Simultaneous observations of falling snow from CloudSat further suggest that climate models over-estimate snowfall frequency and accumulation across the Arctic hinting that model cloud biases may be partially linked to the overly efficient removal of liquid water by falling snow.  Our understanding of the factors that govern Arctic energy balance, however, remains hampered by observational limitations including the unsettling fact that nearly 60% of the emitted thermal energy in the Arctic resides at wavelengths that have never been systematically measured from space.  The need for spectrally-resolved measurements of far-infrared emission in the Arctic will also be articulated.