05 July 2017

Exploration of Turbulent Heat Fluxes and Wind Stress Curl in WRF and ERA-Interim during Wintertime Mesoscale Wind Events Around Southeastern Greenland

Science

Identify wind regimes over the ocean adjacent to southeastern Greenland in 10 years of ERA-Interim and WRF data and assess the surface turbulent fluxes associated with these wind regimes.

Impact

The results presented in this paper demonstrate the variability in surface turbulent fluxes over the ocean around southeastern Greenland in response to different wind regimes including barrier winds and westerly and easterly tip jets. The fluxes in ERA-I and WRF differ mainly in response to differences in the surface state over sea ice and highlights the importance of accurate representation of sea ice concentration and thickness.

Summary

The strong, mesoscale tip jets and barrier winds that occur off the coast of southeastern Greenland drive large surface turbulent heat fluxes that may impact deep ocean convection. The turbulent fluxes and wind stress curl associated with 10 m wind patterns identified using the self-organizing map technique are investigated for 10 winters (1997–2007, November-December-January-February-March) in the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-I) and a regional simulation using the Weather Research and Forecasting (WRF) model at 50 km. Sensible heat flux differences between WRF and ERA-I are primarily due to differences in near-surface temperature, while latent heat flux differences are driven by both moisture and wind speed differences. The largest turbulent flux differences occur over the marginal ice zone where the fluxes in WRF are larger than in ERA-I due to specified sea ice thickness that influences the near-surface atmospheric temperature and moisture; WRF has larger magnitude wind stress curl over the Irminger Sea. Patterns of strong westerly tip jet with barrier flow are most likely to impact preconditioning and convection in the Irminger Sea compared to other manifestations of westerly tip jets, and easterly tip jets are expected to have localized ocean impacts south of Cape Farewell. 

Contact
John Cassano
University of Colorado at Boulder