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COSMO_2005

COSMO General Meeting Zürich, 20 - 23 September 2005. Report on Workpackage 3.2.1.1. Operational implementation of the multi-layer soil model. Erdmann Heise Bodo Ritter and Reinhold Schrodin German Weather Service. COSMO_2005. Page 1 (11). DWD 15 Sep 2005.

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COSMO_2005

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  1. COSMO General Meeting Zürich, 20 - 23 September 2005 Report on Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Erdmann Heise Bodo Ritter and Reinhold Schrodin German Weather Service COSMO_2005 Page 1 (11) DWD 15 Sep 2005

  2. Operational implementation of the multi-layer soil model Structure of the multi-layer soil model for temperature (left, 7 active layers) and for soil water content (right, 6 active layers). COSMO_2005 Page 2 (11) DWD 15 Sep 2005

  3. Operational implementation of the multi-layer soil model • The lower boundary conditions are: a) For the thermal part an 8th layer with constant temperature (annual mean near surface temperature) is added. b) For soil water content the lower boundary condition is a flux condition: the gravitational flux • is accounted for, but fluxes due to soil moisture gradients are neglected. • The effect of freezing/melting in the soil is taken into account. • The snow module is improved compared to the operational version, but it is still a one-layer model. • The whole soil model is still strictly one-dimensional, i. e., no horizontal transports are considered. • The multi-layer soil model is in operational use in the global model GME of the German Weather Service since September 2004, and it is used in the quasi-operational parallel run of the forthcoming operational LM-version, the LME, since January 2005. COSMO_2005 Page 3 (11) DWD 15 Sep 2005

  4. Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Two problems were noted in the GME-runs: 1) In March 2005 excessive low temperatures were simulated over an old snow pack in southern Germany. The problem seems to be caused by the prescribed constant snow density. Work is in progress to implement a time dependent formulation of snow density. An aging function (compression) is combined with a density reduction due to falling snow. 2) There is a tendency to produce 2Δt-waves of small (< 1 K) amplitude in the surface temperature. In GME an unfavourable coupling with atmospheric temperatures at grid-points with excessive large roughness lengths led to very large (> 20 m/s) amplitudes in diagnosed gusts. In the moment this problem is fixed by restricting the roughness length to values < 5 m. But a more in-depth evaluation of the basic problems is necessary. COSMO_2005 Page 4 (11) DWD 15 Sep 2005

  5. Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Verification of soil temperature prediction over Germany In Germany there is a network of stations regularly reporting temperature at different depths in the soil. For 11 August 2005, 06.00 UTC the following figures show measured and predicted (by LME) temperatures. The initial time of the forecast is 11 August 00.00 UTC for all figures. COSMO_2005 Page 5 (11) DWD 15 Sep 2005

  6. Operational implementation of the multi-layer soil model Temperatures at a depth of 5 cm (observation) and 6 cm (simulation) observation simulation COSMO_2005 Page 6 (11) DWD 15 Sep 2005

  7. Operational implementation of the multi-layer soil model Temperatures at a depth of 20 cm (observation) and 18 cm (simulation) observation simulation COSMO_2005 Page 7 (11) DWD 15 Sep 2005

  8. Operational implementation of the multi-layer soil model Temperatures at a depth of 50 cm (observation) and 54 cm (simulation) observation simulation COSMO_2005 Page 8 (11) DWD 15 Sep 2005

  9. Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Verification of soil temperature prediction over Germany In general the figures show a satisfactory agreement between the simulations and the corresponding observations. The main observed features are covered quite well. COSMO_2005 Page 9 (11) DWD 15 Sep 2005

  10. Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Of special concern for a soil model with deep active layers is the possible occurrence of a long-term drift. Therefore, average results for LME are monitored: Soil temperatures (0C) averaged over LME-area: COSMO_2005 Page 10 (11) DWD 15 Sep 2005

  11. Workpackage 3.2.1.1 Operational implementation of the multi-layer soil model Soil water content (Vol. %) averaged over LME-area Up to now no problems have been noted in the long-term behaviour. The workpackage is finished. COSMO_2005 Page 11 (11) DWD 15 Sep 2005

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