Modelling surface fluxes at the Earth's poles
The Earth's poles are particularly vulnerable to climate change. Due to the inhospitable environment, measurements of atmospheric and other parameters are limited. In order to compensate, models are frequently used in combination with satellite observations to assess and forecast the state of both the atmosphere and cryosphere. Scientists with the Swedish Meteorological and Hydrological Institute (SMHI) and their counterparts in Northern Europe endeavoured to improve these models in the framework of the IOMASA I project. Specifically, they re-examined the parameterisation of turbulent fluxes of heat, moisture and momentum at the surface. SMHI drew on empirical evidence from measurement campaigns carried out over a variety of surfaces. The variability in the data could not be fully explained by the Richardson number, which forms the current basis for correction functions in models. Going a step further, SMHI incorporated an additional stability parameter, based on the Brunt-Väisälä frequency, as well as surface roughness length into the parameterisation scheme in order to account for other atmospheric phenomena affecting the fluxes. The results of their work were integrated into HIRLAM, the High resolution limited area model used for short-range weather forecasting by several Northern European meteorological institutes, including SMHI. Further research will address combining the new surface scheme with the latest snow and ice parameterisations in order to further improve our knowledge of weather and climate in polar regions.
