Energy balance closure in the Southwest Amazon forest site—a statistical approach

2018 ◽  
Vol 136 (3-4) ◽  
pp. 1209-1219 ◽  
Author(s):  
Renata Gonçalves Aguiar ◽  
Carlo Ralph De Musis ◽  
Leonardo José Gonçalves Aguiar ◽  
Mariano Martínez-Espinosa ◽  
Graciela Redies Fischer
Keyword(s):  
Energy Balance ◽  
Statistical Approach ◽  
Forest Site ◽  
Amazon Forest ◽  
Energy Balance Closure

scholarly journals Analysis of the energy balance closure over a FLUXNET boreal forest in Finland

2010 ◽  
Vol 7 (3) ◽  
pp. 2683-2707
Author(s):  
J. M. Sánchez ◽  
V. Caselles ◽  
E. M. Rubio
Keyword(s):  
Energy Balance ◽  
Boreal Forest ◽  
Energy Budget ◽  
Friction Velocity ◽  
Average Energy ◽  
Surface Energy Budget ◽  
Forest Site ◽  
Energy Balance Closure ◽  
Hourly Data ◽  
Averaging Time

Abstract. The imbalance in the surface energy budget, when using eddy-covariance techniques to measure turbulent fluxes, is still an unresolved problem. Important progresses have been reported in recent years identifying potential reasons for this lack of energy balance closure. In this paper we focus on the data collected in a FLUXNET boreal forest site in Sodankylä, Finland. Using one month half-hourly data, an average Energy Balance Ratio (EBR) of 0.72 is obtained. The inclusion of the heat storage terms in the energy budget yields an improvement of about 6% in the total closure. The sensitivity of the energy balance closure to the turbulence intensity is analysed in terms of the friction velocity, and atmospheric stability/instability conditions. Significant better closure is obtained for high values of the friction velocity and unstable conditions. The mismatch in variable footprints for different fluxes is checked by analysing the dependence of the closure on wind direction. The inhomogeneities of the emplacement surrounding the flux tower induce a critical decrease in the EBR of up to 30% for specific wind directions. After filtering all unfavourable conditions, EBR=0.94. This is a reasonable good result for the energy balance closure. However there is still a 6% of the available energy unaccounted. Part of this remaining imbalance could be justified as the impossibility of the 30 min averaging time to capture the low frequency flux contributions, since the closure is improved by a 5% when the averaging time is expanded to 2 h.

scholarly journals Analysis of the energy balance closure over a FLUXNET boreal forest in Finland

2010 ◽  
Vol 14 (8) ◽  
pp. 1487-1497 ◽  
Author(s):  
J. M. Sánchez ◽  
V. Caselles ◽  
E. M. Rubio
Keyword(s):  
Energy Balance ◽  
Boreal Forest ◽  
Energy Budget ◽  
Friction Velocity ◽  
Average Energy ◽  
Surface Energy Budget ◽  
Forest Site ◽  
Energy Balance Closure ◽  
Hourly Data ◽  
Averaging Time

Abstract. The imbalance in the surface energy budget, when using eddy-covariance techniques to measure turbulent fluxes, is still an unresolved problem. Important progresses have been reported in recent years identifying potential reasons for this lack of energy balance closure. In this paper we focus on the data collected in a FLUXNET boreal forest site in Sodankylä, Finland. Using one month half-hourly data, an average Energy Balance Ratio (EBR) of 0.72 is obtained. The inclusion of the heat storage terms in the energy budget yields an improvement of about 6% in the total closure. The sensitivity of the energy balance closure to the turbulence intensity is analysed in terms of the friction velocity, and atmospheric stability/instability conditions. Significant better closure is obtained for high values of the friction velocity and unstable conditions. The mismatch in variable footprints for different fluxes is checked by analysing the dependence of the closure on wind direction. The inhomogeneities of the emplacement surrounding the flux tower induce a critical decrease in the EBR of up to 30% for specific wind directions. After filtering all unfavourable conditions, EBR=0.94. This is a reasonable good result for the energy balance closure. However there is still a 6% of the available energy unaccounted. Part of this remaining imbalance could be justified as the impossibility of the 30 min averaging time to capture the low frequency flux contributions, since the closure is improved by a 5% when the averaging time is expanded to 2 h.

scholarly journals An empirical-analytical model of the vertical wind speed profile above and within an Amazon forest site

2015 ◽  
Vol 23 (1) ◽  
pp. 158-164 ◽  
Author(s):  
Cledenilson Mendonça de Souza ◽  
Cléo Quaresma Dias-Júnior ◽  
Júlio Tóta ◽  
Leonardo Deane de Abreu Sá
Keyword(s):  
Wind Speed ◽  
Analytical Model ◽  
Vertical Wind ◽  
Forest Site ◽  
Amazon Forest ◽  
Speed Profile ◽  
Wind Speed Profile ◽  
Vertical Wind Speed

scholarly journals Energy balance closure at FLUXNET sites

2002 ◽  
Vol 113 (1-4) ◽  
pp. 223-243 ◽  
Author(s):  
Kell Wilson ◽  
Allen Goldstein ◽  
Eva Falge ◽  
Marc Aubinet ◽  
Dennis Baldocchi ◽  
...  
Keyword(s):  
Energy Balance ◽  
Energy Balance Closure

scholarly journals Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

2017 ◽  
Vol 21 (7) ◽  
pp. 3401-3415 ◽  
Author(s):  
Nobuhle P. Majozi ◽  
Chris M. Mannaerts ◽  
Abel Ramoelo ◽  
Renaud Mathieu ◽  
Alecia Nickless ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Surface Energy Balance ◽  
Sensible Heat Flux ◽  
Dry Season ◽  
Energy Balance Closure ◽  
Net Radiation ◽  
Wet Season

Abstract. Flux towers provide essential terrestrial climate, water, and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based Earth observation and monitoring efforts, such as assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. In this paper, 15 years of Skukuza eddy covariance data, i.e. from 2000 to 2014, were analysed for surface energy balance closure (EBC) and partitioning. The surface energy balance closure was evaluated using the ordinary least squares regression (OLS) of turbulent energy fluxes (sensible (H) and latent heat (LE)) against available energy (net radiation (Rn) less soil heat (G)), and the energy balance ratio (EBR). Partitioning of the surface energy during the wet and dry seasons was also investigated, as well as how it is affected by atmospheric vapour pressure deficit (VPD), and net radiation. After filtering years with low-quality data (2004–2008), our results show an overall mean EBR of 0.93. Seasonal variations of EBR also showed the wet season with 1.17 and spring (1.02) being closest to unity, with the dry season (0.70) having the highest imbalance. Nocturnal surface energy closure was very low at 0.26, and this was linked to low friction velocity during night-time, with results showing an increase in closure with increase in friction velocity. The energy partition analysis showed that sensible heat flux is the dominant portion of net radiation, especially between March and October, followed by latent heat flux, and lastly the soil heat flux, and during the wet season where latent heat flux dominated sensible heat flux. An increase in net radiation was characterized by an increase in both LE and H, with LE showing a higher rate of increase than H in the wet season, and the reverse happening during the dry season. An increase in VPD is correlated with a decrease in LE and increase in H during the wet season, and an increase in both fluxes during the dry season.

scholarly journals Energy balance measurements over a banana orchard in the Semiarid region in the Northeast of Brazil

2009 ◽  
Vol 44 (11) ◽  
pp. 1365-1373 ◽  
Author(s):  
Carlos Antonio Costa dos Santos ◽  
Bernardo Barbosa da Silva ◽  
Tantravahi Venkata Ramana Rao ◽  
Christopher Michael Usher Neale
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Heat Fluxes ◽  
Irrigation District ◽  
Semiarid Region ◽  
Energy Balance Closure ◽  
Wet Season ◽  
Growing Seasons ◽  
Eddy Covariance System

The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively.

scholarly journals Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

2016 ◽  
Author(s):  
Nobuhle P. Majozi ◽  
Chris M. Mannaerts ◽  
Abel Ramoelo ◽  
Renaud Mathieu ◽  
Alecia Nickless ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Radiation Budget ◽  
Energy Balance Closure ◽  
Flux Tower ◽  
The Impact

Abstract. Flux tower sites and data are in great demand to provide essential terrestrial climate, water and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based earth observation and monitoring efforts, such as for example assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. Surface energy budget methods for ET estimation rely to a large extend on the basic assumption of a surface energy balance closure, assuming the full conversion of net solar radiation reaching the land surface into soil heat conduction and turbulent fluxes, i.e. the sensible (or convection) and latent heat components of the energy balance. Evapotranspiration is the conversion of the latent heat exchange fraction of the balance. In this paper, the Skukuza flux tower data were analysed in order to verify their use for validation of satellite–based evapotranspiration methods, under development in South Africa.Data series from 2000 until 2014 were used in the analysis. The energy balance ratio (EBR) concept, defined as the ratio between the sum of the turbulent convective and latent heat fluxes and radiation minus soil heat was used. At first typical diurnal patterns of EB partitioning were derived for four different seasons, well illustrating how this savannah-type biome responses to the weather conditions. Also the particular behaviour of the EB components during sunrise and sunset conditions, being important but usually neglected periods of energy transitions and inversions were noted and analysed. Annual estimates of the surface energy balance and its components were generated, including an evaluation of the balance closure. The seasonal variations were also investigated as well as the impact of nocturnal observations on the overall EB behaviour.

On the way to realistic large eddy simulations – A comparison of virtual measurements with CHEESEHEAD19 field measurements

2021 ◽  
Author(s):  
Luise Wanner ◽  
Sreenath Paleri ◽  
Johannes Speidel ◽  
Ankur Desai ◽  
Matthias Sühring ◽  
...  
Keyword(s):  
Energy Balance ◽  
Eddy Covariance ◽  
Field Measurements ◽  
Transport Processes ◽  
Large Eddy Simulations ◽  
Surface Model ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Large Eddy ◽  
Eddy Covariance Measurements

<p>Large-eddy simulations are useful tools to study transport processes by mesoscale structures in the atmospheric boundary layer, since in contrast to single-tower eddy covariance measurements, they provide not only temporally but also spatially highly resolved information. Therefore, they are well suited to study the energy balance closure problem, for which the mesoscale transport of latent and sensible heat, triggered by heterogeneous ecosystems, is suspected to be a major cause. However, this requires simulations that are as realistic as possible and thus allow a comparison of real measurements in the field and virtual measurements in the simulation.<br>During the Chequamegon Heterogeneous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors (CHEESEHEAD) experiment in the summer of 2019, a heterogeneous 10x10 square km domain was intensively sampled across scales. This data offers a unique possibility to set up large-eddy simulations with realistic surface heterogeneity. We use PALM to simulate two days and an area of 40 by 40 square kilometers incorporating the CHEESEHEAD site. The large scale atmospheric forcings to inform the boundary conditions are determined from the NCEP HRRR product. As the lower boundary condition, we use a soil and land-surface model coupled with a plant-canopy model, which we adapt to the CHEESEHEAD area based on ground-based and airborne measurements of plant physiological data.<br>In this study, we investigate how well the simulations match with real measurements by comparing simulated profiles and virtual tower measurements with field measurements from radiosonde ascents, lidar measurements of three-dimensional wind and water vapor, eddy-covariance measurements from the 400 meter tower in the center of the study domain, as well as from typical eddy-covariance stations distributed through the study area. This way, we investigate how realistic the simulations actually are and to what extent the knowledge gained from them concerning the energy balance closure problem can be transferred to field measurements.</p>

scholarly journals Some aspects of the energy balance closure problem

2006 ◽  
Vol 6 (12) ◽  
pp. 4395-4402 ◽  
Author(s):  
T. Foken ◽  
F. Wimmer ◽  
M. Mauder ◽  
C. Thomas ◽  
C. Liebethal
Keyword(s):  
Surface Layer ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Low Frequency ◽  
Turbulent Fluxes ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Considerable Influence ◽  
Turbulence Spectrum ◽  
Eddy Covariance Method

Abstract. After briefly discussing several reasons for the energy balance closure problem in the surface layer, the paper focuses on the influence of the low frequency part of the turbulence spectrum on the residual. Changes in the turbulent fluxes in this part of the turbulence spectrum were found to have a significant influence on the changes of the residual. Using the ogive method, it was found that the eddy-covariance method underestimates turbulent fluxes in the case of ogives converging for measuring times longer than the typical averaging interval of 30 min. Additionally, the eddy-covariance method underestimates turbulent fluxes for maximal ogive functions within the averaging interval, both mainly due to advection and non-steady state conditions. This has a considerable influence on the use of the eddy-covariance method.

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