A comparison of the atmospheric conditions at Eureka, Canada, and Barrow, Alaska (2006-2008)

It is now well understood that the Arctic is particularly sensitive to climate change. Arctic sea ice is already undergoing significant changes. Some of the recent decrease in sea ice extent is due to changes in the surface energy budget, including the effect of clouds. Accurate ground-based measurements of atmospheric and cloud properties are valuable for estimating components of the surface energy budget. In this paper, measurements made between 2006 and 2008 at the Canadian Network for the Detection of Arctic Change (CANDAC) site at Eureka, Nunavut, Canada (80 degrees N, 86 degrees W) and the Atmospheric Radiation Measurement (ARM) program site at Barrow, Alaska (71 degrees N, 156 degrees W) are used to examine differences in the atmospheres over the two sites, including the temperature, humidity, winds, and the downwelling longwave radiation flux. A method is developed to convert infrared radiances to downwelling longwave fluxes since broadband measurements of flux were not available at Eureka during the study period; the method is validated by comparing the fluxes at Barrow to independent measurements made by a pyrgeometer. Comparisons of the derived fluxes show significant differences between the two sites. Eureka is consistently colder and drier than Barrow, and the infrared effect of clouds on the surface energy budget is less. To examine the meteorological conditions that cause such differences, the ERA-Interim reanalysis model is used; it is chosen over other models because it provides the best reproduction of longwave radiation at the surface. We find that the location of Eureka predisposes it to cold and dry air masses from the central Arctic Ocean and the Greenland Ice Sheet. In contrast, the air masses at Barrow come from a variety of directions, some of which are relatively warm and moist.