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Science Rendezvous > Posters
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New estimates of the large-scale Arctic energy budget.
David Porter, John Cassano, Mark Serreze
CIRES, ATOC, NSIDC
A best estimate of the current energy budget of the north polar cap (the region north of 70 deg. N) is synthesized through combining data from next-generation atmospheric reanalyses and satellite retrievals. For the period 2000-2005, monthly means from the Clouds and the Earth's Radiant Energy System (CERES) data set are considered to provide the most-reliable top-of-atmosphere (TOA) radiation budget. The remaining components of the energy budget, comprising, the vertically-integrated energy storage, horizontal transport divergence of energy, and the net heat transfer (the net surface flux) between the atmospheric and subsurface columns, are diagnosed using data from the Japanese 25-year Reanalysis Project (JRA) and the NCEP/NCAR Reanalysis (NRA) from the same time period.
The annual cycle of energy budget components for the polar cap averages are fairly consistent between the JRA and NRA, but with some systematic differences. Monthly time-changes in the atmospheric energy storage term are small and very similar in each reanalysis. CERES provides the most reliable data for the TOA radiation budget. JRA depicts an annual mean surface flux annual-mean of 14 W m-2 (upward, directed into the atmospheric column), compared to only 5 W m-2 in NRA. Most of this difference seems to emerge from differences in sea-ice and albedo interactions. Horizontal atmospheric energy flux divergence calculated using mass-corrected flux values contains artifacts leading to unphysical results. We argue that backing out the energy flux divergence as a residual from the net surface heat flux and time-change in energy storage from each reanalysis, and the TOA radiation budget from CERES, provides for more physically realistic results. Comparing results from the different data sets provides useful estimates of uncertainly. We view the development of improved mass-correction techniques as a priority.
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