Regional Simulations of Arctic Boundary Layer during Fall Refreezing

Regional simulations were made using Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) to model atmospheric evolution in the Arctic during the Sea State field experiment in October 2015. It was observed that the sea ice freeze-up occurred because of the air-sea-ice interaction. This combined observation-model study is focused on 1) a general evaluation of the simulations, including the ABL structure and surface energy budget; 2) the interaction of the arctic boundary layer (ABL) and sea ice, including impact of mesoscale advection on surface heat transfer and cloud-radiation feedbacks on the ocean heat loss.

Two simulations are made in the Beaufort/Chukchi seas where the Sea State field program was conducted. One uses the sea ice condition provided by ACNFS (Arctic Cap Nowcast/Forecast System); the other adopts a simple 3 layer sea ice model to simulate the sea ice temperature. The SHEBA (Surface Heat Energy Balance) surface flux parameterization is implemented into COAMPS. The simulation domain is configured to contain three grid meshes (45 km, 15 km, and 5km) with 60 levels in the vertical. The model provides 24 h twice daily simulations between 1 Oct. and 10 Nov. Overall, the ABL structure compares reasonably well with the observations. Mesoscale variations of surface fluxes closely follow the observed trends. In particular, simulated sea ice temperature from the simple sea ice model captures the general trends of three freezeup periods observed during the ice transits of Sikuliaq R/V. The study is still going on and more results will be reported during the AGU Fall Meeting.