Parameterisation of snow and ice albedo in the ECHAM5 General Circulation Model (GCM).
Snow and ice albedo is known to be crucial for heat exchange at high latitudes. Even so, the way snow and ice albedo is parameterised in GCMs today is strongly simplified. By developing characteristic spectral albedo curves for different snow and sea-ice surfaces, and combine this with ground truth and satellite data, we want to improve the albedo parameterisation, by introducing spectral resolution and developing more realistic decay functions.
This year activity includes the collection of data, the intercomparison of already existing models, and the validation of the best model. The work consists of two parts, one dealing with snow on ground and the other with sea ice. The collected time series data over snow covered surfaces include a 20 year time series from Ny-Ålesund, Svalbard, three years of data from Col de Porte, French Alps, six years of data from six stations in the Former Soviet and 12 years of data from Barrow, Alaska. The sea-ice part is covered by data from the Russian Drifting Ice stations in the Arctic Ocean, and the high quality one year data from the SHEBA experiment, also in the Arctic Ocean. Snow and sea-ice albedo parameterisations from 8 different global climate models are compared and validated against these datasets. The models include ECHAM5, UKMO, ECMWF, CLASS, ISAB, GISS, BATS and an one-dimensional thermodynamic sea-ice model by Ebert and Curry, 1993. For comparison a completely data-based regression model is built and compared to the parameterisations in the global climate models.
Albedo and reflectance data with spectral resolution is also collected, and this includes several datasets from the Svalbard area, data from the SHEBA experiment and also data from the Alps and Antarctic. This data will be used to develop characteristic spectral reflectance curves for each key cryospheric surface. For snow we want to develop one curve for each of the classes defined by the International Classification of Seasonal Snow on the Ground by Colbeck