Models simulate snow and ice thermodynamics over a high Arctic lake
The state of the art development of numerical weather prediction (NWP) model are either increase the temporal and spatial resolutions or improve detailed physical processes. FMI has applied two models: a high-resolution, time-dependent snow/ice thermodynamic model (HIGHTSI) and a quasi-steady two-layer model on top of a lake model (FLake) to investigate the evolution of snow and ice thicknesses and temperature in an Arctic lake.
The model experiments were performed for an Arctic lake, Kilpisjärvi located in Finnish Lapland (69°03’N 20°50’E). The modelled snow and ice thickness from HIGHTSI and FLake showed very good agreement with observations, and differences between the models were small.
The in situ observations and a Numerical Weather Prediction model (HIRLAM) were used for the forcing data. Two major questions are examined concerning these models: the sensitivity to atmospheric forcing, and the feasibility to couple with NWP models for improvement of weather forecasting. The research focus was in the influence of the accuracy of the forcing data on the accuracy of the simulated snow and ice thickness and surface temperature.
The onset of ice melting was delayed in both models likely due to albedo parameterizations. HIGHTSI was better for ice thickness and ice-breakup date, while FLake gave better freezing date. Both HIGHTSI and FLake produced warm biases into the modelled surface temperature, typically so for a stable atmospheric boundary layer. Provided with good atmospheric forcing, FLake reproduces quite well the main features of snow and ice thermodynamics including the freezing and ice breakup dates. It is widely used in NWP models. But due to the two-layer approach (i.e. low vertical resolution), for FLake it is difficult to reproduce the detailed time evolution of snow and ice surface temperature. HIGHTSI works better for this, but still further research is needed to reproduce high frequency variations. For NWP and climate modelling, further research is needed to achieve good compromise between the lake ice model resolution and the computational efficiency, as well as to solve the lake ice and snow initialization problem.
More information:
Bin Cheng, Senior Researcher, bin.cheng@fmi.fiEkaterina Kourzeneva, Researcher, ekaterina.kurzeneva@fmi.fi
http://www.borenv.net/BER/pdfs/preprints/Yang.pdf
Yang Y., Cheng, B., Kourzeneva, E., Semmler, T., Rontu, R., Leppäranta, M. Shirasawa, K., and Li, Z. 2013. Modelling experiments on air-snow-ice interactions over a high Arctic lake, Boreal Environment Research,