Modeling of Snow Packs at Urban and Suburban Sites, based on the EPiCC Montreal Field Experiment

The NEW-RPN model, a coupled system including a multi-layer snow model (SNTHERM) and the sea ice model used in the Meteorological Service of Canada (MSC) operational forecasting system, was evaluated in a one-dimensional mode using meteorological observations collected during 1997-98 from SHEBA’s Pittsburgh site in the Arctic Ocean. Results show that NEW-RPN better agrees with observations for the timing of snow depletion and for ice thickness. The mean value of snow thermal conductivity (0.39 W m-1K-1) is within the range of reported observations for SHEBA but larger than 0.31 W m-1K-1 that is commonly used in single-layer snow models. Of particular interest in NEW-RPN’s simulation is the strong temperature stratification of the snowpack, which indicate that a multi-layer snow model is needed in the SHEBA scenario. Based on observations, NEW-RPN’s overestimation of snow depth may be related to other processes, such as small-scale horizontal variability of snow depth and blowing snow processes. Therefore, a 1-D blowing snow model, called PIEKTUK, has been incorporated into this snow/sea- ice coupled system. Intercomparison of simulations performed with and without this effect shows that including blowing snow significantly improves the simulation of snow depth and of temperature at the snow/ice interface, but slightly degrades the simulated sea ice thickness. Several sensitivity analyses have demonstrated that a threshold wind speed of 9 m s-1 better fits the SHEBA data for snow depth, ice thickness, and temperature at snow/ice interface. Total erosion due to blowing snow is found to be as large as 56 mm of snow water equivalent and leads to a decrease (5 cm in average) in snow depth, leading to a shortening of the duration of snow cover by approximately 4 days, to a slight increase of 1.4 cm in average in ice thickness and to a temperature decrease of 0.9 K.