1. Hirlam1D; Statusreport Esbjörn Olsson SMHI/Sundsvall Presented at: Cost 722 Larnaca meeting 19-21 may 2005

2. Hirlam1D; Statusreport Contents: New physics - surface Initialization/data-assimilation Examples

3. Hirlam1D; Statusreport New physics - Surface The new surface scheme is based on an earlier Hirlam-ISBA-scheme, but with separate snow- temperature and a new treatment of the forest. The force-restore of heat in ISBA is replaced by heat conduction. Snow and trees have their own prognostic temperatures. In the new scheme the gridbox is divided into seven different tiles: water, ice, snowfree open land, snowfree low vegetation, snowfree forest, open land with snow and forest with snow (on the ground).

4. Hirlam1D; Statusreport New physics - Surface For all land tiles: prognostic temperatures at 1.0, 7.2 and 43.2 cm depth. The two snow-tiles are treated separatly. Besides temperature, also albedo, density and water content are calculated. There is only one layer of snow. If the snow is deep only the top layer is thermally active. Snow-melting starts at 0 degrees and the water is contained in the snowpack until it reaches a critical level, then the water goes down to the ground.

5. Hirlam1D; Statusreport New physics - Surface Snow-albedo varies between 0.5 for old and wet snow, up to 0.85 for new snow.

6. Hirlam1D; Statusreport New physics - Surface In the forest-tile a lot of prognostic variables are under concern. The snow is treated in the same way as for open land, but the vertical fluxes are calculated the same way as for the snow-free part of the forest. The surface fluxes are calculated between the ground (snow/snowfree) and the air around the trees, the atmosphere only ”feels” the air around the trees. The radiation that reaches the surface depends on how much ”trees” that are shadowing the ground.

7. Hirlam1D; Statusreport New physics - Surface

8. Hirlam1D; Statusreport Initialization/data-assimilation ISBA-analysis of surface temperature och moisture using observed temp and humidity at 2m. Ground temperatures are updated hourly using heat conduction.

9. Hirlam1D; Statusreport Initialization/data-assimilation Problems: –One observed temperature at 2m shall provide startvalues for number of surface-, snow- and forest- temperatures. Not really solved yet. –Information about starting snow-conditions (depth/coverage) is a bit uncertain.

10. Hirlam1D; Statusreport Example