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Projected changes in Eurasian and Arctic summer cyclones under global warming in the Bergen climate model |
Yvan Joseph ORSOLINI,Asgeir SORTEBERG |
Norwegian Institute for Air Research, Kjeller, Norway,Geophysical Institute, University of Bergen; Bjerknes Centre for Climate Research, Bergen, Norway |
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Abstract Using the coupled ocean-atmosphere Bergen Climate Model, and a Lagrangian vorticity-based cyclone tracking method, we investigate current climate summer cyclones in the northern hemisphere and their change by the end of the 21st century, with a focus on northern Eurasia and the Arctic. The two scenarios A1B and A2 for increasing greenhouse gas concentrations are considered. In the model projections, the total number of cyclones in the northern hemisphere is reduced by about 3-4%, but the Arctic Ocean and adjacent coastal regions harbour slightly more and slightly stronger summer storms, compared to the model current climate. This increase occurs in conjunction with an increase in the high-latitude zonal winds and in the meridional temperature gradient between the warming land and the ocean across Northern Eurasia. Deficiencies in climate model representations of the summer storm tracks at high latitudes are also outlined, and the need for further model inter-comparison studies is emphasized.
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Received: 31 October 2008
Revised: 22 December 2008
Accepted: 05 January 2009
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