Analysis of surface energy balance closure over heterogeneous surfaces

Kim, Soojin; Lee, Younghee; Kim, Kyu Rang; Park, Young-San

doi:10.1007/s13143-014-0045-2

Cited by 14 publications

(12 citation statements)

References 36 publications

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“…For example, convective flux occurs when warm air ( > [T]) is rising ( > 0), or cool air ( < [T ]) is subsiding ( < 0) where is time-averaged temperature and [T ] is time-space-averaged temperature. The EBR at both sites showed seasonal variation with the highest value in summer and lowest in winter, which is consistent with previous studies (Wilson et al, 2002;Kim et al, 2014). Comparison of EBR between two sites shows higher EBR at G4 except for winter.…”

Section: Energy Balance Ratiosupporting

confidence: 91%

Analysis of local wind induced by surface heterogeneity and sloping terrain near Nakdong river

Choi

Lee

Cho

et al. 2015

Asia-Pacific J Atmos Sci

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Local wind near river has been analyzed using data collected from nine automatic weather stations (AWS) and two flux stations near Gumi Weir, Nakdong River, for one year. Different onset time of river breeze at east and west river sides and spatial extension of divergent flow suggest that local wind at study area is generated by both the sloping terrain and the differential heating between the river and the land. Divergent (Convergent) flow is observed over the river during the daytime (nighttime). Wind divergence during the daytime is largest in summer and smallest in winter. Weak wind speed and large temperature difference in summer provide favorable condition for wind divergence. The strength of the divergent flow decreases rapidly with increasing wind speed for winds perpendicular to the river. The energy balance closure is evaluated by calculating the seasonal energy balance ratio (EBR), which at two flux sites ranges from 0.43 to 0.60 with the maximum in summer and the minimum in winter. To examine the influence of local circulation on EBR, we calculate the EBR in terms of divergence during the daytime in summer. The mean EBR in the large divergence case is lower than that in the small divergence case by 0.04 and 0.01 at west and east of river, respectively, indicating that local circulation is not main cause for low EBR at these sites.

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Section: Energy Balance Ratiosupporting

confidence: 91%

Analysis of local wind induced by surface heterogeneity and sloping terrain near Nakdong river

Choi

Lee

Cho

et al. 2015

Asia-Pacific J Atmos Sci

Self Cite

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“…The present study found an energy balance closure ratio of 0.91 and R 2 of 0.73. This result is consistent with the 70-90% closure observed across the globe (Barr, Morgenstern, Black, McCaughey, & Nesic, 2006;Foken, 2008;Kim, Lee, Kim, & Park, 2014;Wilson et al, 2002). Results show that the available energy was the bigger flux compared with sum of H and LE.…”

Section: Relationship Between Et and Environmental Variablessupporting

confidence: 90%

Biophysical controls of water vapour and energy fluxes: Towards the development of biome scale predictive models of evapotranspiration in the Albany Thicket, South Africa

et al. 2018

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An understanding of factors modulating water and energy fluxes partitioning over vegetated surfaces is important in a context of global environmental changes. The study evaluated the patterns of water vapour and energy fluxes to enable the development of biome scale predictive evapotranspiration (ET) models over the Albany thicket vegetation. Environmental constraints to ET were assessed by examining the response of ET to biotic and abiotic factors with the latter accounting for >50% variability in ET. Bulk parameters were used to evaluate the integrated impact of biophysical factors on fluxes. The surface conductance (G s ) for use in the Penman-Monteith equation and the Priestley-Taylor coefficient (α) for application in the modified Priestley-Taylor model were modelled as a function of environmental variables.A predictive ET equation developed for the area was validated. On an annual scale, 62% of net radiation was consumed by sensible heat flux, and α was <1, indicating that the area was water limited. The decoupling factor (0.005) suggested strong connection between the canopy and the boundary layer. The patterns of ET and vapour pressure deficit suggest strong ET control through stomatal conductance. The prediction of ET as a function of leaf area index and reference evapotranspiration was better able to simulate observed ET (root mean square error [RMSE] 0.28 mm day −1 ) than application of the Penman-Monteith equation using modelled G s (RMSE of 0.59-0.62 mm day −1 ) when average ET was 0.87 mm day −1 . The modified Priestley-Taylor equation did not perform well because ET was strongly coupled to vapour pressure deficit and surface conductance.

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“…We used the flux footprint prediction online tool of a simple two-dimensional parameterization (Kljun et al, 2015, http://geography.swansea.ac.uk/nkljun/ ffp/www/, last access: 17 July 2018). The footprint parameterization uses the Lagrangian stochastic particle dispersion model (Kljun et al, 2002). As input parameters to the model, we used displacement height,…”

Section: Footprint Analyses and Micro-topographymentioning

confidence: 99%

Evaluating multi-year, multi-site data on the energy balance closure of eddy-covariance flux measurements at cropland sites in southwestern Germany

et al. 2019

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Abstract. The energy balance of eddy-covariance (EC) measurements is typically not closed, resulting in one of the main challenges in evaluating and interpreting EC flux data. Energy balance closure (EBC) is crucial for validating and improving regional and global climate models. To investigate the nature of the gap in EBC for agroecosystems, we analyzed EC measurements from two climatically contrasting regions (Kraichgau – KR – and Swabian Jura – SJ) in southwestern Germany. Data were taken at six fully equipped EC sites from 2010 to 2017. The gap in EBC was quantified by ordinary linear regression, relating the energy balance ratio (EBR), calculated as the quotient of turbulent fluxes and available energy, to the residual energy term. In order to examine potential reasons for differences in EBC, we compared the EBC under varying environmental conditions and investigated a wide range of possible controls. Overall, the variation in EBC was found to be higher during winter than summer. Moreover, we determined that the site had a statistically significant effect on EBC but no significant effect on either crop or region (KR vs SJ). The time-variable footprints of all EC stations were estimated based on data measured in 2015, complimented by micro-topographic analyses along the prevailing wind direction. The smallest mean annual energy balance gap was 17 % in KR and 13 % in SJ. Highest EBRs were mostly found for winds from the prevailing wind direction. The spread of EBRs distinctly narrowed under unstable atmospheric conditions, strong buoyancy, and high friction velocities. Smaller footprint areas led to better EBC due to increasing homogeneity. Flow distortions caused by the back head of the anemometer negatively affected EBC during corresponding wind conditions.

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Analysis of surface energy balance closure over heterogeneous surfaces

Cited by 14 publications

References 36 publications

Analysis of local wind induced by surface heterogeneity and sloping terrain near Nakdong river

Analysis of local wind induced by surface heterogeneity and sloping terrain near Nakdong river

Biophysical controls of water vapour and energy fluxes: Towards the development of biome scale predictive models of evapotranspiration in the Albany Thicket, South Africa

Evaluating multi-year, multi-site data on the energy balance closure of eddy-covariance flux measurements at cropland sites in southwestern Germany

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