COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Lake Parameterisation Scheme FLake within COSMO An Update Dmitrii Mironov and Hermann Asensio German Weather Service, Offenbach am Main, Germany (with contribution from Alexander Smalla and Ulrich Blahak)

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy FLake within COSMO-EU/DE of DWD Since 15 December 2010 Flake is used operationally at DWD within the COSMO-EU (Europe) configuration of the COSMO model (ca. 7 km mesh size). In the present operational configuration, the bottom sediment module is switched off (heat flux at the water-bottom sediment interface is zero) and the effect of snow above the lake ice is accounted for implicitly through an empirical temperature dependence of the ice surface albedo with respect to solar radiation. The surface fluxes of momentum and of sensible and latent heat are computed with the operational COSMO-model surface-layer scheme (Raschendorfer 1999, 2001). Results from pre-operational testing of FLake within COSMO-EU proved to be neutral to slightly positive. Verification against observational data indicate an improvement of some scores such as 2m-temperature in regions where many lakes are present (e.g. Scandinavia). The use of FLake allows to avoid some unwanted situations, e.g. an artificial cold air outbreak. This may occur in winter when a lake that is frozen in reality (low surface temperature) is treated as open water (high surface temperature) within COSMO due to the shortcomings of water surface temperature analysis scheme. Flake is being tested within COSMO-DE of DWD (ca. 2.8 km mesh size). Results from a parallel experiments (that includes the entire data assimilation cycle and actually mimics the routine COSMO-DE) look satisfactory. The performance of FLake within COSMO-EU/DE is monitored.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance FLake prognostic variables (T_WML_LK, T_MNW_LK, T_BOT_LK, H_ML_LK, C_T_LK, T_ICE, H_ICE) are retrieved from the data bank (initial values form 00 UTC COSMO-EU/DE forecast) and plotted Sanity check is performed and a warning message is sent if things go wrong (OK is sent if things look good) Monitoring results from the last week are available via DWD Intranet, results from the last months are stored in the archive

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance (cont’d) Mixed-layer temperature from 00UTC+00h COSMO-EU forecast for the sub-domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance (cont’d) Mixed-layer depth from 00UTC+00h COSMO-EU forecast for the sub- domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance (cont’d) Ice surface temperature and ice thickness from 00UTC+00h COSMO-EU forecast for the sub-domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters The software is developed (Hermann Asensio) to generate external- parameter fields of lake fraction, FR_LAKE, and lake depth, DEPTH_LK, for an arbitrary numerical domain. GLC2000 or GlobeCover physiographic data sets (30 arc sec and 10 arc sec pixel size, respectively) in combination with the GLOBE orography data set (30 arc sec pixel size) are used to generate FR_LAKE, and the lake- depth data set (30 arc sec pixel size) developed by Kourzeneva (2010) is used to generate DEPTH_LK. A careful consistency check is performed to avoid mismatches between FR_LAKE, DEPTH_LK and the external-parameter field of lake fraction, FR_LAND. The raw external-parameter data sets and the procedure used to generate FR_LAKE and DEPTH_LK are described in the updated COSMO-model documentation.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-depth external-parameter field based on the lake-depth data from Kourzeneva (2010) and GlobCover physiographic data. The horizontal size of the COSMO-model (target) grid is ca. 7 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-depth external-parameter field based on the lake-depth data from Kourzeneva (2010) and GlobCover physiographic data. The horizontal size of the COSMO-model grid is ca. 2.8 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-fraction external-parameter field based on the lake-depth data from Kourzeneva (2010) and GlobCover physiographic data. The horizontal size of the COSMO-model grid is ca. 7 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Documentation COSMO Model Documentation update (D. Mironov & H. Asensio) A brief description of the lake parameterisation scheme FLake (model documentation) is included into Part II of COSMO Documentation (c/o Jan- Peter Schulz); a detailed description of FLake (scientific documentation) is given in Mironov (2008, COSMO Technical Report No. 11) Generation of external parameters is described in Part II of COSMO Documentation (c/o Hermann Asensio, Jan-Peter Schulz) A cold-start initialization procedure is described in Part V (int2lm) of COSMO Documentation (c/o Ulrich Schättler); the cold-start initialisation of FLake variables should be performed only once for each COSMO-model configuration in terms of the model domain and horizontal resolution Users are strongly encouraged to look through the Documentation! (this is compulsory if changes are to be made in int2lm or in the external-parameter software)

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Outlook Operational use of FLake within COSMO-DE Update of external-parameter fields Use FLake within a tiled surface scheme (work is underway, Ekaterina Machulskaya and Jürgen Helmert) References Kirillin, G., J. Hochschild, D.Mironov, A. Terzhevik, S.Golosov, and G. Nützmann, 2011: FLake-Global: Online lake model with worldwide coverage. Environ. Modell. Softw., 26, Kourzeneva, E., 2010: External data for lake parameterization in Numerical Weather Prediction and climate modeling. Boreal Env. Res., 15, Mironov, D. V., 2008: Parameterization of lakes in numerical weather prediction. Description of a lake model. COSMO Technical Report, No. 11, Deutscher Wetterdienst, Offenbach am Main, Germany, 41 pp. Mironov, D., E. Heise, E. Kourzeneva, B. Ritter, N. Schneider, and A. Terzhevik, 2010: Implementation of the lake parameterisation scheme FLake into the numerical weather prediction model COSMO. Boreal Env. Res., 15,

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Application of FLake to Tropical Lakes (Alexander Smalla and Ulrich Blahak, DWD) Project SWFDP “Severe Weather Forecast Demonstration Project” is aimed at quantitative precipitation forecast for East Africa (co-operation between DWD, Meteo France International, and Kenya Meteorological Department). FLake is applied within high-resolution COSMO model (horizontal mesh size ca. 2.8 km) to compute the surface temperature of Lake Victoria. In summary … FLake showed satisfactory performance. The scheme, incl. generation of external-parameter fields, was easy to use.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Application of FLake to Tropical Lakes (cont’d) Surface temperature (T_g, dgr C) from the 18h (left) and 36h (right) COSMO-model forecasts initialised at 00 UTC 19 March 2011.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Application of FLake to Tropical Lakes (cont’d) Surface temperature (T_g, K) along the 1S zonal cross-section the from the 24h (left) and 36h (right) COSMO-model forecasts initialised at 00 UTC 19 March Lake Land

COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Thank you for your attention! Acknowledgements: Jochen Förstner, Helmut Frank, Thomas Hanisch, Jürgen Helmert, Ekaterina Kourzeneva, Martin Lange, Ekaterina Machulskaya, Van Tan Nguyen, Bodo Ritter, Ulrich Schättler, Jan-Peter Schulz

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy …

Monitoring of FLake performance (cont’d) Mean temperature of the water column from 00UTC+00h COSMO-EU forecast for the sub-domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance (cont’d) Bottom temperature from 00UTC+00h COSMO-EU forecast for the sub- domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy Monitoring of FLake performance (cont’d) Shape factor with respect to the temperature profile in the thermocline from 00UTC+00h COSMO-EU forecast for the sub-domain “Northern Europe”.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-fraction external-parameter field based on the lake-depth data from Kourzeneva (2010) and GlobCover physiographic data. The horizontal size of the COSMO-model grid is ca. 2.8 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-depth external-parameter field based on the lake-depth data from Kourzeneva (2010) and GLC2000 physiographic data. The horizontal size of the COSMO-model grid is ca. 7 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-fraction external-parameter field based on the lake-depth data from Kourzeneva (2010) and GLC2000 physiographic data. The horizontal size of the COSMO-model grid is ca. 7 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-depth external-parameter field based on the lake-depth data from Kourzeneva (2010) and GLC2000 physiographic data. The horizontal size of the COSMO-model grid is ca. 2.8 km.

FLake update | COSMO General Meeting, 5 – 9 September 2011, Rome, Italy External parameters (cont’d) The lake-fraction external-parameter field based on the lake-depth data from Kourzeneva (2010) and GLC2000 physiographic data. The horizontal size of the COSMO-model grid is ca. 2.8 km.