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WRF model experiments on the atmospheric boundary layer over the Ronne polynya

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Citation:
Lorenz, T. , Vihma, T. , Weiss, A. , Lüpkes, C. , Lachlan-Cope, T. , Hartmann, J. , Birnbaum, G. , Ladkin, R. , King, J. and Tetzlaff, A. (2012): WRF model experiments on the atmospheric boundary layer over the Ronne polynya , SCAR Open Science Conference, Portland, USA, 16 July 2012 - 19 July 2012 .
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Abstract:

The Weather Research and Forecasting (WRF) Model ARW V3.3 was applied to simulate the atmospheric boundary layer (ABL) modification over the Ronne Polynya in March 2010. The model results were validated against airborne observations from two research aircrafts. These observations were made during the campaign Joint Airborne Study of the Peninsula Region (JASPER) by the British Antarctic Survey and the Alfred Wegener Institute. Throughout the 36-h-long simulation period on 1-2 March, there was a south to south-westerly mean flow, coming from the ice shelf towards the polynya, which was approximately 10 km wide. Three model experiments were made, all of them receiving boundary conditions from the ECMWF operational analyses. The only difference between the model runs was in the sea ice concentration. The first model run was conducted with the sea ice concentration of the ECMWF operational analysis, which was available in a resolution of 16 km. For the second model run, a sea ice dataset with a much finer resolution was used, the AMSR-E dataset refined by the ARTIST Sea Ice algorithm, in a resolution of 6.25 km. In the third model run the polynya was manually replaced by a compact sea ice cover. Thereby the sensitivity of the ABL modification over the polynya to the sea ice data was analyzed. It is shown that the finer spatial resolution of the AMSR-E sea ice data allows a better simulation of the local polynya effects on the ABL, especially an increase in air temperature, humidity, and near-surface wind speeds. The validation against the observations revealed a cold temperature bias in the model within the ABL under stable to near-neutral conditions, and above the ABL regardless of stratification. The surface fluxes of heat and moisture and the ABL height were investigated along three cross-sections across the polynya. Additionally, an ice breeze from the sea ice surrounding the polynya towards the center of the polynya, and back to the sea ice at higher altitudes, was found in the WRF simulation with the AMSR-E sea ice dataset.

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