Momentum and heat fluxes over lakes Tämnaren and Råksjö determined by the bulk-aerodynamic and eddy-correlation methods

Heikinheimo, Martti; Kangas, Markku; Tourula, Tapio; Venäläinen, Ari; Tattari, Sirkka

doi:10.1016/s0168-1923(99)00121-5

Cited by 54 publications

(43 citation statements)

References 24 publications

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“…A recent study (Heikinheimo et al, 1999) found that the similarity theory applied in all atmospheric stability situations, thus confirming earlier work such as Businger et al (1971) and Crawford (1965). McNaughton and Laubach (1998), in their similarity studies, conclude that Bowen ratio measurements will be satisfactory except with quite intense inversions and that using the assumption will only result in minor error.…”

Section: Bowen Ratio Theorysupporting

confidence: 84%

Estimating evapotranspiration from a reed bed using the Bowen ratio energy balance method

Peacock

Hess

2004

Hydrological Processes

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Abstract:An increase in demand for water for agricultural and domestic use, combined with new legislation regarding the water needs of natural habitats, has led to an increased requirement for accurate calculations of hydrological fluxes through wetlands. Evapotranspiration is one of the most important but least well understood fluxes in wetland hydrology. Research has been carried out on Stodmarsh National Nature Reserve in Kent, UK, a Ramsar site containing the largest reed beds in southern England. The objective was to quantify water loss through evapotranspiration on the site to allow more effective management of water levels and maintenance of maximum conservation potential for bird life. The Bowen ratio energy balance approach was employed, which is one of the most accurate ways of measuring evapotranspiration but has been rarely used on reed beds. These measurements were used with Penman-Monteith reference evapotranspiration in order to create crop coefficients. It was found that crop coefficients were inconsistent from day to day but were generally less than unity. The inconsistency was thought to be caused by variations in meteorological conditions: e.g. significant differences in crop coefficients were found between days with high radiation and a dry canopy, compared with days with low radiation and a wet canopy. Canopy interception of precipitation was particularly important, with crop coefficients being significantly higher on wet days, possibly due to the higher rates of evaporation of intercepted water due to the lack of stomatal resistance.

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Section: Bowen Ratio Theorysupporting

confidence: 84%

Estimating evapotranspiration from a reed bed using the Bowen ratio energy balance method

Peacock

Hess

2004

Hydrological Processes

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“…This is in sharp contrast with boreal forest ecosystems, where the ratio usually exceeds 1 and creates a deep convective boundary layer in daytime [e.g., Markkanen et al , 2001]. However, the results on H and LE are in accordance with those for other lakes, for example for two boreal Swedish lakes studied by Heikinheimo et al [1999] and Venäläinen et al [1999]. Also the diurnal patterns of LE as well as of H with opposite phases were similar in Lake Valkea‐Kotinen and in the Swedish lakes.…”

Section: Resultsmentioning

confidence: 59%

“…The main focus of this study is on the turbulent exchange of CO 2 between an isolated lake and the atmosphere, but we consider also momentum flux and sensible and latent heat fluxes. On these latter ones a lot of earlier information exists [e.g., Heikinheimo et al , 1999; Venäläinen et al , 1999] that can be used also for validation of the gathered data. For example, under conditions where momentum flux is not directed downward, EC fluxes are not expected to be a direct function of local surface exchange processes [ Eugster et al , 2003].…”

Section: Introductionmentioning

confidence: 99%

Eddy covariance measurements of carbon exchange and latent and sensible heat fluxes over a boreal lake for a full open‐water period

et al. 2006

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[1] Long-term measurements of sensible and latent heat and carbon dioxide fluxes were performed over a boreal lake in southern Finland using the direct micrometeorological eddy covariance (EC) technique. The water column was sampled weekly for dissolved carbon dioxide, and the CO 2 flux was estimated also applying the concentration gradient method. Temperature and oxygen profiles of the lake were measured twice a week. The measurements covered one full open-water period from April to November 2003, and it is the longest continuous CO 2 record ever measured over a lake by EC. The sensible heat flux H was positive, that is, from the lake to the atmosphere, except in May, when it was >0 W/m 2 at night and <0 W/m 2 in daytime. The latent heat flux dominated clearly over H in spring and summer; that is, the Bowen ratio was less than 1. Highermoment turbulence statistics proved to be efficient in detection of frequent nonstationary situations. Applying the statistical criteria for CO 2 concentration and vertical wind speed, averaging over a 5-min period and selecting only the wind direction with longest fetch, we could obtain lake-representative CO 2 fluxes. Footprint analysis based on a closure model revealed that the source areas were relatively short because of the presence of turbulence generated by the surrounding forest, compared to a larger lake with an extended smooth surface. We observed a net CO 2 source of 0.2-0.4 mmol m À2 s À1 excluding July, when the flux was closer to zero. The results are consistent with the gradient method, based on more infrequent sampling, and both methods gave the same average flux, 0.2 mmol m À2 s À1 , over the whole open-water period.

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“…The simulated surface temperature calculation takes into account atmospheric stability, because the bulk transfer coefficient C H for sensible heat contains information about the efficiency of turbulent transport between the surface and the reference level. The transfer coefficient depends on the roughness length of wind speed (z 0 ), the roughness of temperature (z T ), and the stability of the lowest surface layer (J) (Heikinheimo et al, 1999):…”

Section: A New Index: Ntdimentioning

confidence: 99%

Diurnal surface temperature difference index derived from ground-based meteorological measurements for assessment of moisture availability

Mohamed

Kimura

Shinoda

et al. 2011

Journal of Arid Environments

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Momentum and heat fluxes over lakes Tämnaren and Råksjö determined by the bulk-aerodynamic and eddy-correlation methods

Cited by 54 publications

References 24 publications

Estimating evapotranspiration from a reed bed using the Bowen ratio energy balance method

Estimating evapotranspiration from a reed bed using the Bowen ratio energy balance method

Eddy covariance measurements of carbon exchange and latent and sensible heat fluxes over a boreal lake for a full open‐water period

Diurnal surface temperature difference index derived from ground-based meteorological measurements for assessment of moisture availability

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