The interactions between the atmosphere and the underlying surface are among the most important factors in climate modelling. Sea and land surfaces dominate globally, but on regional scales, the interactions between the atmosphere and lake surface can be a major driver in regional and local climate, especially at locations with high lake area density.
Earlier, many climate models used the nearest sea-point approach to represent lakes, where the lake surface temperature and ice conditions were taken from the nearest sea-point. However, this approach has major problems; for example, the lakes in northern Europe usually freeze before the nearest sea area, because the lakes are shallower and consist of freshwater. With the nearest sea-point approach, lakes continue to emit heat and moisture to the atmosphere far longer during early winter, thus causing artificial heat and moisture fluxes to the atmosphere.
Recently, climate models have started to include interactive lake modules. In a cooperation between GERICS and the Finnish Meteorological Institute REMO has been further developed to include an interactive lake module called FLake. FLake is fully coupled with REMO and it calculates all lake related parameters for the lake fractions in each grid box.
The surface orography of Finland including lakes and rivers. High lake density areas needs interactive lakes for climate modelling purposes.
REMO with FLake (REMO-FLake) has been tested over Fenno-Scandinavia in a 35-year long simulation. The results show that overall the new model version improves the representation of the Fenno-Scandinavian climate in terms of 2-m temperature and precipitation. Lake surface temperature, ice conditions, snow depths over lakes and ice season lengths are also realistically captured by the model.
For more information about REMO-FLake please visit:
- Pietikäinen, J.-P., Markkanen, T., Sieck, K., Jacob, D., Korhonen, J., Räisänen, P., Gao, Y., Ahola, J., Korhonen, H., Laaksonen, A., and Kaurola, J. (2017) The regional climate model REMO (v2015) coupled with the 1-D freshwater model FLake (v1): Fenno-Scandinavian climate and lakes, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-245, in review.