LAKE MODEL INTERCOMPARISON PROJECT______

The launch of LakeMIP I

This project was launched after the Workshop “Parameterization of Lakes in Numerical Weather Prediction and Climate Modelling” held September 18-20, 2008, St. Petersburg (Zelenogorsk), Russia:

Lake parameterization Workshop, Sept 2008: http://netfam.fmi.fi/Lake08/

Scientists from different research groups (e.g. NWP/RCM, Climate, and Limnology) identified the needs for an intercomparison of existing lake models to simulate not only lake surface temperature (including ice and snow cover) but also the evolution of internal vertical thermal profiles.

Although a number of lake model exists, it has been agreed that one should first focus on few lake models for testing purposes such as these parameterised in atmospheric models (NWP/RCM) thus providing for time varying lower boundary conditions. These tests would ultimately indicate directions for further research and developments.

It is also recognised that a minimum number of issues should be addressed in order to evaluate these lake models and to create a benchmark for the different parameterizations and approaches.

The first reasonable step implied the intercomparison of single-column (i.e. one-dimensional) lake model forced by heat and momentum fluxes (computed on the basis of observed atmospheric variables) in a stand-alone mode over a fixed number of lake types. The second step would deal with the coupling of these lake models to atmospheric models (either single column as well as 3D NWP, RCM, or SCM) in order to cover a broader range of lake conditions.

To focus on the first step, this site has provided for relevant information regarding this intercomparison initiative:

• numerical lake models formulations
• available lake data (Lake Surface Temperatures (LST) and thermal profiles), seasonal ice and snow (thicknesses and covers)
• time series of available atmospheric forcing including surface air temperature, moisture, wind speed and direction, but also when available surface fluxes of incoming downward solar and thermal infrared radiation, as well as sensible and latent heat
• lake depth and morphometry  

PRELUDE 

It is a well established fact that lakes play an important role on the local weather, even at a regional scale for larger lakes, and thus on climate. The hydrological regime of lakes is a function of current climate that makes efficient to use them as indicators of paleoclimate. The large lakes are crucially important for regional economies, so that their ecological state changing under climate evolution and anthropogenic impact is of strong interest. The interaction between atmosphere and lakes is still represented in a rudimentary way in mathematical models for weather and climate. Until recently (before the pioneering work by Bonan in 1995) many studies of this interaction have been based on one-way coupling, i.e. lake models running with precomputed (measured) atmospheric forcing or in atmospheric models using oversimplified surface scheme specifications for lake-rich regions. Currently, the horizontal grid spacing of atmospheric models allows a number of lakes to be explicitly resolved. Hence, physically-sound lake parameterizations are needed in numerical weather prediction (NWP) and climate models (GCM, RCM, SCM). However, these parameterizations must be computationally efficient, especially in NWP. A reasonable compromise between these two requirements are 1-D lake models. A number of studies has proven that they are satisfactory applicable for a wide range of lakes. Up to now, many lake models have been embedded to surface schemes of atmospheric models (Bonan, 2002; Mironov, 2008; Goyette et al., 2000; etc.). These models cover a range of formulations among which we find 1-D resolving and models with parameterized vertical temperature profile (Mironov, 2008). The resolving models may use either sophisticated eddy diffusivity schemes (typically k-ε or its extensions) or diagnostic formulations, involving dependence on Richardson number. Despite some intercomparison studies of 1-D lake models for particular lakes (i.e. Perroud and Goyette, 2009), there is still a large degree of uncertainty on what lake model types are optimal for certain environmental applications, and what are the important physical processes, that are crucial to take into account in that models in order to well reproduce the lake-atmosphere interaction. Recent projects on intercomparison of surface schemes in weather and climate models (PILPS, SNOWMIP, SNOWMIP2) under the auspices of WMO/PCMDI have demonstrated that this kind of study is efficient in answering questions raised above. The LakeMIP project is going to inherit to a large degree the methodologies of these projects.

SHORT DESCRIPTION OF THE PROJECT

The main goals aimed at the identification of the key processes that should be represented in different applications of lake models (e.g. climate and weather simulation, lake physics and ecology), and the development/improvement of their physical parameterizations. During the first phase of the project (LakeMIP1) the number of participants (lake models) has been limited for manageability. The list of participants, institutions, countries (models) is as follows: 1. Marjorie Perroud, University of Geneva, Switzerland (Simstrat model);  2. Viktor Stepanenko, Moscow State University, Russia (Viktor Stepanenko model); 3. Dmitrii Mironov, Deutscher Wetterdienst, Germany (FLake);  4. Xing Fang, Auburn University in Alabama, USA (MINLAKE96) ;  5. Klaus D. Joehnk,CSIRO Land and Water, Black Mountain, Canberra, ACT, Australia, (Klaus Joehnk model);  6. Wim Thiery, Earth and Environmental Sciences Regional Climate Studies, KU Leuven.

CITED REFERENCES

Bonan, G. B., 1995: Sensitivity of a GCM simulation to inclusion of inland water surfaces, J. Clim., 8, 2691–2704.

Bonan, G. B., K. W. Oleson, M. Vertenstein, S. Levis, X. Zeng, Y. Dai, R. E. Dickinson, and Z.-L. Yang, 2002: The land surface climatology of the Community Land Model coupled to the NCAR Community Climate Model. J. Clim., 15, 3123-3149

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.

Goyette, S., N. A. McFarlane, and G. M. Flato, 2000: Application of the Canadian Regional Climate Model to the Laurentian Great Lakes region: Implementation of a lake model. Atmos. Ocean, 38, 481-503.

Perroud, M., S. Goyette, A. Martynov, M. Beniston, O. Anneville, 2009 : Simulation of multiannual thermal profiles in deep Lake Geneva: a one-dimensional lake-model intercomparison study. Limnol. Oceanogr., 55(9), 1574-1594.

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