Testing boundary layer and cloud parameterizations in the Polar Weather Research and Forecasting model using data from the Norwegian Young Sea ICE (N-ICE2015) cruise

Abstract:

Cloud properties and radiative and turbulent fluxes are difficult to measure over sea ice, particularly during polar winter, due to the difficulty in deploying and maintaining instruments. This lack of measurements makes model validation difficult. Previous studies using observational data have shown that clouds are particularly difficult to model over Arctic sea ice. The Norwegian Young Sea Ice (N-ICE2015) field experiment took place from January through June 2015 onboard the R/V Lance, a research vessel frozen into first-year sea ice north of Svalbard. Instruments onboard measured surface meteorology, twice-daily radiosonde profiles, radiative fluxes, turbulent fluxes, and cloud properties. These observations are used here to evaluate a number of commonly used boundary layer and cloud parameterizations in the polar version of the Weather Research and Forecasting model (Polar WRF) over young sea ice in three seasons. A series of synoptic storms were observed during the winter season with temperatures ranging between -40 and 0 C. These storms resulted in rapid changes in surface properties and near-surface atmospheric conditions, including the temperature and humidity profiles and radiative properties. Preliminary comparisons during the winter storms show that, while the surface pressure is well simulated, the magnitude of the turbulent fluxes is often too large. Also, the spring warm-up period occurred too soon in the model simulations, with the temperatures reaching freezing about 10 days before the observations. The performance of Polar WRF using combinations of four cloud microphysics schemes and three boundary layer schemes will be presented, with emphasis on the winter storm periods during the N-ICE2015 observational period.