Objectif Lakes significantly affect the structure of the atmospheric surface layer and therefore the surface fluxes of heat, water vapour and momentum. The interaction of the atmosphere with the underlying surface is strongly dependent on the lake surface temperature (the water surface temperature, or the surface temperature of snow or ice if a lake is frozen). Lakes also modify the structure and the transport properties of the atmospheric surface layer. These issues are still poorly understood. In most numerical modelling systems for environmental applications, most notably numerical weather prediction and climate modelling systems, the effect of lakes is either entirely ignored or is parameterised very crudely. The problem calls for further investigation, in particular, due to the increase of the horizontal resolution in most numerical modelling systems that are envisaged in the near future.The proposed project is aimed at(i) developing a physically sound and computationally efficient lake model capable of predicting the lake surface temperature on the diurnal to seasonal time scales;(ii) developing an improved atmospheric surface-layer parameterisation scheme that accounts for specific features of the surface layer over lakes, and;(iii) providing improved understanding and quantifying the effect of lakes on the surface temperature and humidity and on the surface fluxes of momentum, heat and water vapour.A two-layer model to predict the temperature changes and mixing conditions in lakes will be developed, using the idea of a parametric representation of the evolving temperature profile. The upper layer is treated as well mixed and vertically homogeneous. The structure of the lower stably stratified layer, the lake thermocline, is parameterised using a polynomial self-similar representation of the temperature profile. An advanced formulation for the mixed-layer depth will be used. A module to compute the heat flux through the water-bottom sediments interface will be developed, based on a self-similar representation of the temperature profile in the sediments. An advance snow-ice module will incorporate refined parameterisations of various complex processes, such as accumulation, aging and melting. An atmospheric surface-layer parameterisation scheme that accounts for specific features of the surface air layer over lakes will be developed. The scheme will include a formulation for the aerodynamic roughness length of the water surface with due regard for a limited fetch, and formulations for the roughness lengths for scalar quantities, such as potential temperature and specific humidity, that account for the essential difference between the roughness lengths for wind and for scalars.To this end, most advanced theoretical ideas will be used, but the focus will be on the simplified formulations that account for most salient features of the roughness of the lake surface. Both the lake model and the surface-layer scheme will be developed in a way to achieve the best compromise between physical realism and computational economy. The lake model and the surface-layer scheme will be verified against empirical data. To this end, the project database will be developed and maintained. It will include comprehensive data sets on the temperature structure in various lakes, on ice and snow cover, and on mean profiles and turbulent fluxes in the atmospheric surface layer over lakes. Both existing data and data from new measurements will be used. New field measurements will be performed in Lake Vendyurskoe, Karelia, Russia, to specifically look at the structure of the temperature field in a shallow lake and on the short-term temperature changes. The new lake model and the surface-layer parameterisation scheme will be integrated into the three-dimensional environments of numerical weather prediction and climate modelling systems, ranging from a non-hydrostatic limited-area model to a hydrostatic global model. Numerical experiments will be carried out to test the performance of and fine-tune new parameterisations.The project results will include(i) an advanced lake model capable of predicting the surface temperature in lakes of various depth on diurnal to seasonal time scales, incorporating a module to predict the vertical temperature structure of a lake, a module to predict the evolution of the ice and snow cover, and a module to describe the interaction of the lake water and bottom sediments;(ii) an advanced atmospheric surface-layer parameterisation scheme that accounts for specific features of the surface air layer over lakes,(iii) results from verification of the lake model and of the surface-layer scheme against observational data;(iv) a comprehensive data set on the temperature structure in various lakes, on ice and snow cover, and on mean profiles and turbulent fluxes in the atmospheric surface layer over lakes;(v) an improved understanding of the role of lakes in the interaction of the atmosphere with the underlying surface. Recommendations towards practical use of the project results will be formulated. Programme(s) IC-INTAS - International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993- Thème(s) 5 - Earth Sciences, Environment, Energy OPEN - OPEN Call Appel à propositions Data not available Régime de financement Data not available Coordinateur German Weather Service Contribution de l’UE Aucune donnée Adresse Frankfurter Str. 135 63067 Offenbach am Main Allemagne Voir sur la carte Coût total Aucune donnée Participants (5) Trier par ordre alphabétique Trier par contribution de l’UE Tout développer Tout réduire Royal Netherlands Meteorological Institute Pays-Bas Contribution de l’UE Aucune donnée Adresse Wilhelminalaan 10 3730 AE De Bilt Voir sur la carte Coût total Aucune donnée Russian Academy of Sciences Russie Contribution de l’UE Aucune donnée Adresse Sevastyanov st., 9 196199 St. Petersburg Voir sur la carte Coût total Aucune donnée Russian Academy of Sciences Russie Contribution de l’UE Aucune donnée Adresse Gubkina Street 8 119991 Moscow Voir sur la carte Coût total Aucune donnée Russian Academy of Sciences Russie Contribution de l’UE Aucune donnée Adresse Alexander Nevsky Street 50 185003 Petrozavodsk Voir sur la carte Coût total Aucune donnée Swedish Meteorological and Hydrological Institute Suède Contribution de l’UE Aucune donnée Adresse 60176 Norrkoping Voir sur la carte Coût total Aucune donnée
