Primary Author: Kvamsto, Nils Gunnar Additional Authors: Byrkjedal, I. Esau
Simulation of High Latitude Climate
Byrkjedal, I. Esau and N. G. Kvamsto
The current general circulation models, including several of those used by the IPCC, show considerable disagreement in simulating present day high latitude climate. This is of major concern and reduces the confidence in future model projections of high latitude climate. The wintertime Arctic climate is characterized by a very shallow stable planetary boundary layer (from a few tenths to a couple hundred meters deep). The boundary layer is capped by a strong inversion. The lowest temperatures are found near the surface while the maximum temperature is found at the top of the inversion, typically at 500-1500 meters. The boundary layer turbulent activity is inhibited by the very stable atmospheric conditions. The very low turbulent activity may cause very low surface temperatures to form. To investigate how turbulent vertical exchange processes in the Arctic boundary layer is represented by the climate models a simulation with high vertical resolution in the lower part of the atmosphere is performed. This reveals that the coarse vertical resolution commonly employed in the climate models are unable to reproduce important exchange processes in the Arctic boundary layer. In the case of our model this results in a warm bias over the Arctic Ocean. By increasing the vertical resolution we achieve a better representation of vertical turbulent exchange processes with the result of reproducing more realistic surface fluxes and surface air temperatures.
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