Mironov, D., Rontu, L., Kourzeneva, E. & Terzhevik, A. 2010: Towards improved representation of lakes in numerical weather prediction and climate models: Introduction to the special issue of Boreal Environment Research. Boreal Env. Res. 15: 97–99.
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Dutra, E., Stepanenko, V. M., Balsamo, G., Viterbo, P., Miranda, P. M. A., Mironov, D. & Schär, C. 2010: An offline study of the impact of lakes on the performance of the ECMWF surface scheme. Boreal Env. Res. 15: 100–112.
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Samuelsson, P., Kourzeneva, E. & Mironov, D. 2010: The impact of lakes on the European climate as simulated by a regional climate model. Boreal Env. Res. 15: 113–129.
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Eerola, K., Rontu, L., Kourzeneva, E. & Shcherbak, E. 2010: A study on effects of lake temperature and ice cover in HIRLAM. Boreal Env. Res. 15: 130–142.
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Martynov, A., Sushama, L. & Laprise, R. 2010: Simulation of temperate freezing lakes by one-dimensional lake models: performance assessment for interactive coupling with regional climate models. Boreal Env. Res. 15: 143–164.
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Kourzeneva, E. 2010: External data for lake parameterization in Numerical Weather Prediction and climate modeling. Boreal Env. Res. 15: 165–177.
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Balsamo, G., Dutra, E., Stepanenko, V. M., Viterbo, P., Miranda, P. M. A. & Mironov, D. 2010: Deriving an effective lake depth from satellite lake surface temperature data: a feasibility study with MODIS data. Boreal Env. Res. 15: 178–190.
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Stepanenko, V. M., Goyette, S., Martynov, A., Perroud, M., Fang, X. & Mironov, D. 2010: First steps of a Lake Model Intercomparison Project: LakeMIP. Boreal Env. Res. 15: 191–202.
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Krinner, G. & Boike, J. 2010: A study of the large-scale climatic effects of a possible disappearance of high-latitude inland water surfaces during the 21st century. Boreal Env. Res. 15: 203–217.
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Mironov, D., Heise, E., Kourzeneva, E., Ritter, B., Schneider, N. & Terzhevik, A. 2010: Implementation of the lake parameterisation scheme FLake into the numerical weather prediction model COSMO. Boreal Env. Res. 15: 218–230.
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Salgado, R. & Le Moigne, P. 2010: Coupling of the FLake model to the Surfex externalized surface model. Boreal Env. Res. 15: 231–244.
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Vörös, M., Istvánovics, V. & Weidinger, T. 2010: Applicability of the FLake model to Lake Balaton. Boreal Env. Res. 15: 245–254.
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Perroud, M. & Goyette, S. 2010: Impact of warmer climate on Lake Geneva water-temperature profiles. Boreal Env. Res. 15: 255–278.
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Kirillin, G. 2010: Modeling the impact of global warming on water temperature and seasonal mixing regimes in small temperate lakes. Boreal Env. Res. 15: 279–293.
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Dutra, E., Stepanenko, V. M., Balsamo, G., Viterbo, P., Miranda, P. M. A., Mironov, D. & Schär, C. 2010: An offline study of the impact of lakes on the performance of the ECMWF surface scheme. Boreal Env. Res. 15: 100–112.

The lake model FLake was incorporated into the European Centre for Medium-Range Weather Forecasts (ECMWF) land-surface scheme HTESSEL. Results from global offline simulations are presented in order to evaluate the model performance in different climates and assess the impact of lake representation on the surface energy balance. The model was forced by ECMWF reanalysis ERA-Interim (1989–2005) near surface meteorology and surface radiation fluxes for the entire globe. Model validation includes lake surface temperatures and lake ice duration. The impact of the snow insulation on lake ice cover duration is discussed, as well as the sensitivity of results to the lake depth. Results show changes in the variation of surface energy storage, and changes in the partition of surface energy fluxes in high latitude and equatorial regions, respectively. General aspects concerning the incorporation of lake models into General Circulation Models for weather forecast and climate modelling are discussed.

Samuelsson, P., Kourzeneva, E. & Mironov, D. 2010: The impact of lakes on the European climate as simulated by a regional climate model. Boreal Env. Res. 15: 113–129.

The impact of lakes on the European climate is considered by analysing two 30-year regional climate model (RCM) simulations. The RCM applied is the Rossby Centre regional climate model RCA3.5. A simulation where all lakes in the model domain are replaced by land surface is compared with a simulation where the effect of lakes is accounted for through the use of the lake model FLake coupled to RCA. The difference in 2m open-land air temperature between the two simulations shows that lakes induce a warming on the European climate for all seasons. The greatest impact is seen during autumn and winter over southern Finland and western Russia where the warming exceeds 1 °C. Locally, e.g. over southern Finland and over Lake Ladoga, the convective precipitation is enhanced by 20%–40% during late summer and early autumn while it is reduced by more than 70% over Lake Ladoga during early summer.

Eerola, K., Rontu, L., Kourzeneva, E. & Shcherbak, E. 2010: A study on effects of lake temperature and ice cover in HIRLAM. Boreal Env. Res. 15: 130–142.

Lake surface temperatures (LST) for a numerical weather prediction (NWP) model can be obtained in several ways: by utilizing climatic information, by assimilating LST observations and by applying lake parametrizations for prediction of LST. We tried these approaches in the High Resolution Limited Area Model (HIRLAM) and show that, indeed, they result in different predicted screen-level temperatures and ice cover. In our experiments, the differences tended to remain local in the atmospheric surface layer over areas close to lakes. Usage of climatic LST information may lead to inaccurate atmospheric temperature forecasts, especially when the lake surface state (frozen/unfrozen) is incorrectly described. Assimilation of the LST observations would produce the most reliable results, but presently such observations are not available for the operational NWP. Use of the Freshwater Lake Model (FLake) as a parametrization scheme in HIRLAM showed promising results, but further development is needed in order to reduce the inertia of the scheme and to improve handling of the lake freezing. Melting of lake ice was not considered in this study.

Martynov, A., Sushama, L. & Laprise, R. 2010: Simulation of temperate freezing lakes by one-dimensional lake models: performance assessment for interactive coupling with regional climate models. Boreal Env. Res. 15: 143–164.

A systematic assessment of the ability of two selected 1-D lake models (the model of S.W. Hostetler and the Freshwater Lake model) to simulate lake surface temperature and fluxes for different lake conditions, corresponding to typical temperate freezing lakes of North America, through a set of offline tests, is presented. Results suggest that both models perform well in shallow lakes, while important differences between modelled and observed water temperatures and ice-cover duration can be noticed in deeper lakes. These differences could be partially attributed to the biases in the driving data and most importantly to the lack of representation of complex processes in the models, such as horizontal transfer of water and heat, ice drift, etc. Sensitivity of the models to lake depth, water transparency, explicit snow and snow/ice albedo is presented and possible ways of improving the performance of the 1-D lake models are proposed.

Kourzeneva, E. 2010: External data for lake parameterization in Numerical Weather Prediction and climate modeling. Boreal Env. Res. 15: 165–177.

Lake parameterizations in atmospheric modeling include a set of external data to indicate and to map physical properties of lakes. The main challenge is the need to consider all the lakes in the atmospheric model domain and to specify the corresponding parameters. For Numerical Weather Prediction (NWP), we also need the data to initialize the lake time-dependent variables (so-called cold start data). The first steps to make the set of lake parameters for the needs of atmospheric modeling are described in this paper. The mean lake depth was chosen to be the key lake parameter for which direct measurements were collected and processed. The Global Land Cover Characteristics (GLCC) dataset was used for mapping, and the mapping method was based on a probabilistic approach. Empirical Probability Density Functions were used to project the lake information onto the target grid of an atmospheric model. The pseudo-periodical regime of the lake model was used to obtain the initial fields of lake variables.

Balsamo, G., Dutra, E., Stepanenko, V. M., Viterbo, P., Miranda, P. M. A. & Mironov, D. 2010: Deriving an effective lake depth from satellite lake surface temperature data: a feasibility study with MODIS data. Boreal Env. Res. 15: 178–190.

Modelling lakes in Numerical Weather Prediction (NWP) is important to produce accurate evaporation rates and surface temperature forecasts. Lake depth is a crucial external parameter for the implementation of lake models into NWP systems, since it controls the dynamical range of lake temperature amplitudes on diurnal to seasonal time scales. However, a global lake-depth dataset does not exist at present. A novel method to derive an effective lake depth on the basis of the remotely-sensed lake water-surface temperature (LWST) is presented here. A technique is proposed to adjust a simple two-layer Fresh-water Lake model (FLake) depth such that simulated annual cycle of LWST matches satellite-based LWST climatology as closely as possible. The method was applied to 47 European lakes and the results show convergence of the solutions. Merits and limitations of this approach are discussed. Preliminary validation of a derived bathymetry of the American Great Lakes is presented.

Stepanenko, V. M., Goyette, S., Martynov, A., Perroud, M., Fang, X. & Mironov, D. 2010: First steps of a Lake Model Intercomparison Project: LakeMIP. Boreal Env. Res. 15: 191–202.

The state-of-the-art in one-dimensional lake modelling is briefly reviewed and the motivation for a Lake Model Intercomparison Project (LakeMIP) is presented. The objectives, methodology and implementation phases of the LakeMIP are outlined. Some results from the first intercomparison study are presented. The lake models used in the study range from a one-layer bulk model to finite-difference models with k-ε turbulence closures. All models tested proved to satisfactorily simulate the seasonal cycle of surface temperature in small Sparkling Lake (Wisconsin, USA). However, problems are encountered in representing vertical mixing through the lake thermocline and the evolution of the near-bottom temperature. Results from simulations of the surface temperature of Lake Michigan are in less gratifying agreement with observational data as compared with the Sparkling Lake test case, which calls for further investigation.

Krinner, G. & Boike, J. 2010: A study of the large-scale climatic effects of a possible disappearance of high-latitude inland water surfaces during the 21st century. Boreal Env. Res. 15: 203–217.

This study evaluates the climatic impact of possible future changes in high-latitude inland water surface (IWS) area. We carried out a set of climate-change experiments with an atmospheric general circulation model in which different scenarios of future changes of IWS extent were prescribed. The simulations are based on the SRES-A1B greenhouse gas emission scenario and represent the transient climatic state at the end of the 21st century. Our results indicate that the impact of a reduction in IWS extent depends on the season considered: the total disappearance of IWS would lead to cooling during cold seasons and to warming in summer. In the annual mean, the cooling effect would be dominant. In an experiment in which the future change of prescribed IWS extent is prescribed as a function of the simulated changes of permafrost extent, we find that these changes are self-consistent in the sense that their effects on the simulated temperature and precipitation patterns would not be contradictory to the underlying scenario of changes in IWS extent. In this 'best guess' simulation, the projected changes in IWS extent would reduce future near-surface warming over large parts of northern Eurasia by about 20% during the cold season, while the impact in North America and during summer is less clear. As a whole, the direct climatic impact of future IWS changes is likely to be moderate.

Mironov, D., Heise, E., Kourzeneva, E., Ritter, B., Schneider, N. & Terzhevik, A. 2010: Implementation of the lake parameterisation scheme FLake into the numerical weather prediction model COSMO. Boreal Env. Res. 15: 218–230.

The application of the lake model FLake to represent the effect of lakes in numerical weather prediction (NWP) and climate models is discussed. As a lake parameterisation scheme FLake is implemented into the limited-area NWP model COSMO. Results from a numerical experiment with the coupled COSMO-FLake system, including the complete COSMO-model data assimilation cycle, indicate a good performance with respect to the lake surface temperature and to the freeze-up of lakes and the ice break-up. The use of FLake removes a significant overestimation of the lake surface temperature during winter that is typical of the routine COSMO sea surface temperature analysis. Some challenging issues are discussed, such as the development of external-parameter fields and the lake temperature spin-up following a cold start of FLake in an NWP or climate model.

Salgado, R. & Le Moigne, P. 2010: Coupling of the FLake model to the Surfex externalized surface model. Boreal Env. Res. 15: 231–244.

The FLake model parameterizes the local-scale energy exchanges between lake surfaces and the atmosphere. FLake simulates the temperature profile as well as the budgets of heat and turbulent kinetic energy in water. Its implementation into the Surfex system, the externalized surface scheme devoted to research and operational forecasts, is presented here. The paper describes a validation of the coupled system Surfex-FLake based on measurements carried out on the Alqueva reservoir in southern Portugal. This paper shows how the use of FLake in the Surfex system improves surface temperature and turbulent fluxes at the water–atmosphere interface and explains the minor changes made in the computation of the shape function in order to adapt the FLake model to warm lakes, like the one used for this study.

Vörös, M., Istvánovics, V. & Weidinger, T. 2010: Applicability of the FLake model to Lake Balaton. Boreal Env. Res. 15: 245–254.

Owing to its uniquely large surface area/depth ratio, the temperature of Lake Balaton is highly sensitive to atmospheric events. In the ALADIN weather prediction model, which is used operationally in Hungary, lakes are not properly represented, as their temperature is initialized from interpolated values of sea surface temperature and considered to be constant for the duration of the forecast. The FLake model as a lake parameterization offers a more detailed but still computationally inexpensive solution to this deficiency. We investigated whether the model could be applied to Lake Balaton. We tested the performance of a standalone version of the FLake model by using observations and atmospheric model data. In the off-line simulations, FLake performed well on Lake Balaton with default settings in predicting surface temperatures, and less well in capturing the bottom water temperatures and stratification.

Perroud, M. & Goyette, S. 2010: Impact of warmer climate on Lake Geneva water-temperature profiles. Boreal Env. Res. 15: 255–278.

The impact of climate warming caused by the increase of greenhouse gases in the atmosphere on the thermal profiles of Lake Geneva, Switzerland, is investigated using a k-ε turbulence lake model. To assess the thermal response of this lake, two sets of 130-year time series of hourly meteorological variables are used to drive the lake model. In the control simulation, the lake model is driven by a series representative of the period 1981–1990, and in the perturbed experiment, deltas derived from outputs of the HIRHAM Regional Climate Model run under the IPCC A2 scenario in the framework of the 5th EU programme PRUDENCE, have been used. Changes in the lake water temperature profiles indicate an increase in monthly epilimnic and hypolimnic temperatures of 2.32–3.8 °C and 2.2–2.33 °C, respectively. The rising of epilimnic temperatures corresponds to 55%–98% of the monthly increase in air temperature. The stratification period lasts longer and the lake stability increases. Thus the lake is likely to retain its mixing regime, but this will be of shorter duration.

Kirillin, G. 2010: Modeling the impact of global warming on water temperature and seasonal mixing regimes in small temperate lakes. Boreal Env. Res. 15: 279–293.

Global warming increases the vertical stability in small lakes and makes a future transition between different mixing regimes possible. In order to estimate this effect, the one-dimensional lake temperature model, FLake, is applied to two lakes located in Berlin, Germany, that have similar morphometrical characteristics but that differ in the mixing regime. The model is driven by long-term meteorological data and by regional climate scenarios. The current rate of increase in the year-round lake temperature of 0.3 °C per decade is found to coincide with the trend in the air temperature. The warming rates are unevenly redistributed over the seasons and across the water column; the strongest warming occurs in winter and slight cooling of the near-bottom waters occurs in summer. In future scenarios, both lakes change their mixing regime to warm monomictic over the course of the century. Successive transitions between poly-, di- and monomictic states reveal themselves through a series of abrupt changes in the near-bottom temperature during summer, which can significantly affect the water–sediment nutrient exchange and the benthic biological communities.