P1.3
Comparing Arctic cloud cover and surface energy fluxes in the ERA-40, SHEBA, and other data sets
Cassie Wheeler, University of Colorado, Boulder, CO; and P. O. G. Persson and M. Shupe
Earth's climate has been changing rapidly in the past few decades. The effects of climate change have been shown to be most noticeable in the Arctic. However, the Arctic environment is poorly understood due to several unique factors: relatively high surface albedo, absence of solar radiation during the polar night, extremely cold and dry conditions, and presence of temperature and humidity inversions. In order to understand the response of the Arctic to a changing climate, studies of trends, processes, and feedbacks utilize models and model-observation hybrid data sets. Hence, the accuracy of the processes and feedbacks in these data sets are important. In this study, data from the ECMWF reanalysis data set (ERA-40) are examined from September 1992 through August 2002 over the Arctic (lat > 65° N). ERA-40 cloud cover and cloud trends over four surface types [sea ice, land, open ocean, and marginal ice zones (MIZ)] are compared to each other and to those at key observation sites, such as the site of the year-long 1997-1998 Surface Heat Budget of the Arctic Ocean (SHEBA) experiment and the observatories for the Study of the Environmental Arctic Change (SEARCH). For instance, the cloud cover and trends at the SHEBA site are representative of those for all sea-ice areas in ERA-40. In addition, comparisons between ERA-40 and observations are made of cloud characteristics, including cloud phase. These are used to understand observation-reanalysis comparisons of cloud radiative forcing and several cloud forcing relationships, such as that between net wintertime longwave radiation and turbulent sensible heat flux. In general, the radiative fluxes in ERA-40 agree well with the observations, but with differences impacting its ability to reproduce these relationships. If such relationships are not represented, the reanalysis data may not be able to produce appropriate responses to changing radiative conditions brought on by climate change.
Poster Session 1, Posters
Monday, 18 May 2009, 5:00 PM-7:00 PM, Wisconsin Ballroom
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