Latent Heat Flux from Small Sheltered Lakes

Venäläinen, Ari; Heikinheimo, Martti; Tourula, Tapio

doi:10.1023/a:1000664615657

Cited by 28 publications

(17 citation statements)

References 9 publications

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“…With this choice, 90% of the maximum wind stress are reached as far as about 640 m downwind from the reservoir edge in the north-western sub-basin for south-westerly winds. This appears to be a reasonable approximation to the wind distributions measured over Lake Råksjön by Venäläinen et al (1998).…”

Section: Simulation Resultssupporting

confidence: 64%

“…As expected, larger deviations mainly occur during the deployment at MP08, where the DWD values are approximately 2 m/s higher than the field measurements. Based on ratios U 03, W /U 03, L over Lake Råksjön and roughness lengths z 0,W , z 0, L as given by Venäläinen et al (1998), it can be shown by logarithmic scaling that it is in fact reasonable to consider the U 16, L values as an approximation to the fully developed values of U 02, W over Spremberg Reservoir. Figure 2 demonstrates that the wind conditions vary considerably during the field measurements, with wind directions initially towards the west (q w ~ 90°) turning towards the north and, finally, north-east to east (q w ~ 247.5°).…”

Section: Field Measurementsmentioning

confidence: 99%

“…However, even if no flow separation occurs at the land-lake transition, the abrupt change of surface roughness causes a disturbance and subsequent re-establishment of the atmospheric boundary layer with gradually increasing wind velocity and stress (Taylor and Lee, 1984;Walmsley et al, 1989). The small Swedish Lake Råksjön, for example, features a maximum fetch length of about 1300 m and is surrounded by dense forest with tree tops > 20 m above the water surface (Venäläinen et al, 1998). Measured wind speeds reach near-constant values as far as 1000 m from shore.…”

Section: Introductionmentioning

confidence: 99%

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Measurements and three-dimensional simulations of flow in a shallow reservoir subject to small-scale wind field inhomogeneities induced by sheltering

Rubbert

Köngeter

2005

Aquat. Sci.

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Spremberg Reservoir is a small and shallow water body where wind sheltering along steep and densely vegetated sections of the shoreline is expected to produce small-scale inhomogeneities of the wind field across the water surface. The potential impacts of these inhomogeneities on the quasi-steady circulation in the main subbasin of the reservoir are investigated in this study by means of a three-dimensional hydrodynamic model. ADCP measurement profiles at three locations are available for comparison. Agreement between characteristic features of the measurements and the simulation data cannot be achieved if uniform winds are applied as boundary conditions, but improves distinctly when sheltering effects are implemented. This is done qualitatively by means of analogy to the separation of flow across a backward fac- Aquat. Sci. 67 (2005) Aquatic Sciences ing step. For south-westerly winds, the modification of the flow tends from a three-dimensional to an essentially horizontal, one-cell circulation. The action of the wind sheltering on the flow is found to rely on (1) the addition of a curl to the background wind field and (2) the weakening of the topological moment along the windward shore. In Spremberg Reservoir the first mechanism appears to prevail for south-westerly winds. The study underlines the need for consideration of small-scale inhomogeneities of the wind field induced by sheltering as a potential source of vorticity in hydrodynamic simulations. Further investigations should be directed towards a physically founded parameterization of the actual wind stress distribution and towards quantifying lake dimensions at which such influences on the circulation pattern tend to be negligible.

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Section: Simulation Resultssupporting

confidence: 64%

Section: Field Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Measurements and three-dimensional simulations of flow in a shallow reservoir subject to small-scale wind field inhomogeneities induced by sheltering

Rubbert

Köngeter

2005

Aquat. Sci.

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“…On the other hand, small lakes exert little influence on the temperature or humidity of the overlying air. Some observations indicate, however, that evaporation can be enhanced over large lakes in situations where the effect of increased wind speed more than compensates for the increased humidity of the air associated with the larger distance traveled by the air over water, for example, Venalainen et al (1998). They also noted that evaporation from lakes fringed with forest would be reduced through sheltering: apparently the reduction in turbulence associated with the reduced wind speeds more than compensates for the increased aerodynamic roughness of the forest.…”

Section: Diffusion Into the Atmospherementioning

confidence: 99%

Evaporation from Lakes

Finch

Hall

2005

Encyclopedia of Hydrological Sciences

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Lakes are an important part of the hydrological cycle, but quantifying the evaporation rates from them is not a trivial task. The amount of radiant energy captured by a lake is generally the dominant control on the annual evaporation rate. At shorter time periods, the major factors affecting lake evaporation are: the albedo, the heat‐storage term of the energy budget, and the atmospheric diffusion processes. The albedo is a function of the solar elevation angle and the proportion of downward diffuse radiation, and can be predicted from empirical relationships. The heat‐storage term can decouple the evaporation rates from the net radiation, but can be estimated simply in the case of well‐mixed water. However, in the situation where the lake becomes thermally stratified, more complex, hydrodynamic models are required. The three commonly used methods of estimating lake evaporation are: mass transfer, energy balance, and combination equations. There are strengths and limitations to each of these methods.

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“…The evaporation from water surfaces is thus often assessed by indirect methods (Finch and Hall, 2005). There are numerous methods based on the Dalton-type empirical equations for the seasonal and daily values of evaporation (Kohler, 1954;Pruitt, 1966;Odrova, 1978) or based on the mass and energy balance methods (Venäläinen et al, 1998;Pienitz et al, 2004). The latent heat flux or the evaporation rate can be also known from the lake model simulations forced by standard meteorological observations or by outputs of a NWP model.…”

Section: The Fildes Peninsulamentioning

confidence: 99%

Thermal regime and components of water balance of lakes in Antarctica at the Fildes peninsula and the Larsemann Hills

Shevnina¹,

Kourzeneva

2017

Tellus A: Dynamic Meteorology and Oceanography

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Thermal regime and water balance components of 12 lakes located at two different parts of the Antarctic (the Fildes peninsula in the Maritime Antarctic and the Larsemann Hills in the continental Antarctica) were studied using the observations from three field campaigns in 2012-2014. The morphometric characteristics of the studied lakes were updated with GPS/echo-sounding surveys, and changes in the length, width and volume of the lakes were revealed in comparison with the previous surveys. The thermal regime of the lakes was also studied by modelling, applying the lake model FLake, which is widely used in different environmental applications but was tested for the first time in the Antarctic conditions. In contrast to boreal lakes, for lakes in Antarctica the modelling results by FLake appeared to be sensitive to the light extinction coefficient. According to simulations, all lakes were mixed down to the bottom for the whole summer; however, the reasons for this are different for shallow and deep lakes. The sensitivity of different methods to calculate evaporation, by the Dalton-type empirical equation and by the atmospheric surface layer block of FLake, was studied. For endorheic lakes, the sensitivity appeared to be large, up to 47% of the total seasonal water volume change, which assumes that FLake has the potential to be used in hydrological applications to calculate evaporation. Seasonal variations of the volume of the lakes in the continental Antarctica are larger than in the Maritime Antarctic. Usually, small and medium-sized lakes accumulate or redistribute water during the warm season. However, the systems of big lakes also release the stored water through the mechanism of abrupt jumps, which simultaneously cause the inflow into the sea of huge amounts of fresh water during short time intervals.

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Latent Heat Flux from Small Sheltered Lakes

Cited by 28 publications

References 9 publications

Measurements and three-dimensional simulations of flow in a shallow reservoir subject to small-scale wind field inhomogeneities induced by sheltering

Measurements and three-dimensional simulations of flow in a shallow reservoir subject to small-scale wind field inhomogeneities induced by sheltering

Evaporation from Lakes

Thermal regime and components of water balance of lakes in Antarctica at the Fildes peninsula and the Larsemann Hills

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