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Fram Strait Marine Cold Air Outbreaks in CARRA and ERA5: Effects on Surface Turbulent Heat Fluxes and the Vertical Structure of the Troposphere
  • Nils Kristina Slättberg,
  • Sandro Dahlke,
  • Marion Maturilli
Nils Kristina Slättberg
Alfred Wegener Institute for Polar and Marine Research

Corresponding Author:nils.slaettberg@awi.de

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Sandro Dahlke
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
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Marion Maturilli
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
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Marine Cold Air Outbreaks (MCAOs) have a profound influence on atmospheric conditions and the surface-atmosphere heat exchange in Fram Strait and Svalbard. Comparing the global reanalysis ERA5 to its novel Arctic counterpart CARRA for November-March 1991-2020, we investigate the surface turbulent heat fluxes and the spatial characteristics of MCAOs throughout the troposphere. We find that the sensible heat flux from the surface to the atmosphere is substantially higher in CARRA, while the latent heat flux is higher in ERA5. For sensible heat flux, the differences scale with the magnitude, leading to maximum disagreement over the ice-free ocean where the flux is high. Accounting for the varying magnitude over different surface types, we find the largest relative disagreement over sea ice. During MCAOs, negative anomalies in temperature and specific humidity are present throughout the entire troposphere in both reanalyses. Meanwhile, positive heat flux anomalies are found in northwestern Fram Strait, where the sensible heat flux from the ocean to the atmosphere is roughly doubled during MCAOs. Around much of Svalbard, sea ice decline has caused positive trends in the surface-atmosphere potential temperature difference forming the basis of the MCAO index, leading to higher heat fluxes. In Fram Strait however, both reanalyses show negative trends in the MCAO index and the heat fluxes in January, when the increase in potential temperature is larger at 850 hPa than at the surface.
14 Mar 2023Submitted to ESS Open Archive
16 Mar 2023Published in ESS Open Archive