Comparison of actual evapotranspiration based on lysimeter, scintillometer and bowen ratio energy balance method

2020 ◽  
Author(s):  
Veronika Forstner ◽  
Matevž Vremec ◽  
Matěj Orság ◽  
Gabriela Pozníková ◽  
Steffen Birk ◽  
...  
Keyword(s):  
Energy Balance ◽  
Land Surface ◽  
Near Infrared ◽  
Agricultural Research ◽  
Sensible Heat Flux ◽  
Bowen Ratio ◽  
Vegetation Period ◽  
The Other ◽  
Actual Evapotranspiration ◽  
Ratio Energy

<p>Evapotranspiration is an important parameter for grassland ecosystems because the (actual) evapotranspiration explains the exchange of water and energy between soil, land surface and atmosphere. Understanding the effects of changing grassland yields on evapotranspiration rates is essential for the assessment of the water- and plant water balance of grassland sites under climate change. However, evapotranspiration is difficult to measure, and the suitability of the various methods strongly depends on the time and spatial scale considered. Thus, the aim of this work is to compare different measurements of actual evapotranspiration (ETa) at a managed alpine grassland site. The study area is located in the northern alps of Austria, at the Agricultural Research and Education Centre Raumberg-Gumpenstein (Styria). Here, the ETa data of a high resolution weighable lysimeters, are compared with ETa data measured by a scintillometer system BLS900 (Scintec, Germany). The system measures sensible heat flux integrated along the near-infrared beam of 880 nm, length of 356 m and height of 6.3 m above grassy surface. The ETa is calculated as a residual from the energy balance equation. Another independent source of ETa data is the Bowen ratio energy balance system (BREB), which is placed roughly in the middle of the scintillometer path and adjacently (few meters) to the lysimeter.</p><p>During the observation period (vegetation period 2018; March-November), ETa calculated from the weighable lysimeter was 573 mm in total and showed the highest absolute value compared to the other measurements. The calculated ETa from the BREB system is 505 mm (including condensation) and 526 mm (excluding condensation).</p><p>At the beginning of the vegetation growth, the scintillometer system measured lower values of ETa than the lysimeter, but higher values than the BREB system. Contrary, at the end of May, the lysimeter ETa showed the lowest values compared to the other two systems. This can be related to the fact that the grass on the lysimeter was cut three times per year, whereas the management of other areas on the experimental site was different. The same effects were observed at the second and third cut, always with the fact that the scintillometer system showed higher values than the BREB system. After two weeks of the first and second cut, the vegetation on the lysimeters was established faster than on the surrounding grassland. As a consequence, the lysimeter ETa showed again the highest values. Only after the third cut at the end of September, the vegetation was slowly growing and the scintillometer as well the BREB system showed higher ETa values till the end of the observation month in November. These results suggest that the evapotranspiration rates are strongly dependent on the management of the grassland, which needs to be considered in the selection and design of evapotranspiration measurements.</p>

scholarly journals On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

2015 ◽  
Vol 12 (8) ◽  
pp. 2311-2326 ◽  
Author(s):  
J. Ingwersen ◽  
K. Imukova ◽  
P. Högy ◽  
T. Streck
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Land Surface Model ◽  
Bowen Ratio ◽  
Surface Model ◽  
Flux Data ◽  
Uncertainty Band

Abstract. The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modelling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure methods uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in southwest Germany in 2011, and the performance of the Jarvis and Ball–Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m−2 (21% of net radiation). Our study shows that it is crucial to account for the uncertainty in EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model–data comparisons.

scholarly journals Actual Evapotranspiration in Suli Alpine Meadow in Northeastern Edge of Qinghai-Tibet Plateau, China

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Jin-kui Wu ◽  
Shi-qiang Zhang ◽  
Hao Wu ◽  
Shi-wei Liu ◽  
Yu Qin ◽  
...  
Keyword(s):  
Energy Balance ◽  
Alpine Meadow ◽  
Bowen Ratio ◽  
Growing Season ◽  
High Elevation ◽  
Actual Evapotranspiration ◽  
Tibet Plateau ◽  
Evapotranspiration Estimation ◽  
Qinghai Tibet Plateau ◽  
Ratio Energy

Actual evapotranspiration was observed by using eddy covariance (EC) technique, calculated by micrometeorological method the Bowen ratio energy balance (BREB) and measured by micro-lysimeter (ML) in the Suli alpine meadow which located in the northeastern edge of Qinghai-Tibet Plateau noted for its high elevation and cold environment during the growing season in 2011. Results showed that the energy balance ratio for half-hour data was 0.74. Without consideration of uncertainty, the evapotranspiration values estimated by BREB, ML, and EC were 270.6 mm, 238.9 mm, and 236.1 mm, respectively. Significant correlation existed between the evapotranspiration results by the three methods. Uncertainties of the evapotranspiration estimation by BREB, ML, and EC were 19.6 mm, 15.6 mm, and 15.1 mm, respectively. Deduced by facts on the natural and vegetation conditions, the value of evapotranspiration should be equal to that of precipitation, that is, about 252 mm. From this point, the evapotranspiration values estimated by the three methods were within a reliable range. The EC method has larger advantage and wider scope for the estimation of evapotranspiration in alpine meadow area.

scholarly journals On the use of the post-closure method uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

2014 ◽  
Vol 11 (12) ◽  
pp. 16911-16951
Author(s):  
J. Ingwersen ◽  
K. Imukova ◽  
P. Högy ◽  
T. Streck
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Bowen Ratio ◽  
Surface Model ◽  
Flux Data ◽  
Uncertainty Band ◽  
Closure Method

Abstract. The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modeling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure method uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in Southwest Germany in 2011, and the performance of the Jarvis and Ball–Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m–2 (21% of net radiation). Our study shows that it is crucial to account for the uncertainty of EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model-data comparisons.

­Actual Evapotranspiration for Sugarcane Based on Bowen Ratio-Energy Balance and Soil Water Balance Models with Optimized Crop Coefficients.

2021 ◽  
Author(s):  
Suelen da Costa Faria Martins ◽  
Marcos Alex dos Santos ◽  
Gustavo Bastos Lyra ◽  
José Leonaldo Souza ◽  
Guilherme Bastos Lyra ◽  
...  
Keyword(s):  
Energy Balance ◽  
Water Balance ◽  
Soil Water ◽  
Bowen Ratio ◽  
Balance Method ◽  
Northeastern Brazil ◽  
Soil Water Balance ◽  
Actual Evapotranspiration ◽  
Crop Coefficients ◽  
Ratio Energy

Abstract Evapotranspiration is an important parameter to evaluate soil water deficit and water use efficiency, especially at places with irregularly distributed precipitation.The aim of this study was to assess the daily actual evapotranspiration (ETa) estimated by the Thornthwaite and Mather soil water balance method adapted for crops (ThM) and by the dual Kc approach with the crop coefficients optimized from inversing modeling and by the adjustment procedure suggested in FAO-56. The models comparison and optimization were performed with actual evapotranspiration determined by the Bowen ratio – energy balance method (ETβ) for sugarcane at full canopy closure grown in Alagoas State, Northeastern Brazil. The objective function of the inverse problem was defined in terms of ETβ and ETa estimated by the ThM and dual Kc method by optimizing single crop coefficient (Kc) and the basal coefficient Kcb, respectively. Both optimized Kcand Kcbwere lower than the adjusted KcFAO56, with optimized Kconly 3% less than the Kc obtained experimentally. ETa estimated by ThM and dual Kc models with optimized crop coefficients (Kc = 1.05 or Kcb = 1.00) had similar high precision (r² >0.79) and accuracy (dm>0.93 and RMSE < 0.30 mm d-1), whereas using the coefficients derived from FAO 56 overestimated ETa in both models.

BOWEN RATIO-ENERGY BALANCE ESTIMATES OF EVAPOTRANSPIRATION AND CROP COEFFICIENT FOR TOMATO PLANTS

1996 ◽  
pp. 121-126
Author(s):  
A.M.R. Abdel-Mawgoud ◽  
S.O. El-Abd ◽  
A.F. Abou-Hadid ◽  
T.C. Hsiao
Keyword(s):  
Energy Balance ◽  
Crop Coefficient ◽  
Bowen Ratio ◽  
Tomato Plants ◽  
Ratio Energy

scholarly journals Bower ratio-energy balance associated errors in vineyards under dripping irrigation

2007 ◽  
Vol 22 (2) ◽  
pp. 233-240 ◽  
Author(s):  
José Monteiro Soares ◽  
Pedro Vieira De Azevedo ◽  
Bernado Barbosa Da Silva
Keyword(s):  
Energy Balance ◽  
Soil Surface ◽  
Field Measurements ◽  
Bowen Ratio ◽  
Global Solar Radiation ◽  
Soil Heat Flux ◽  
Vitis Vinifera L ◽  
Data Logger ◽  
And Storage ◽  
Ratio Energy

This study was conducted at the Bebedouro Experimental Station in Petrolina-PE, Brazil, to evaluate the errors associated to the application of the Bowen ratio-energy balance in a 3-years old vineyard (Vitis vinifera, L), grown in a trellis system, irrigated by dripping. The field measurements were taken during fruiting cycle (July to November, 2001), which was divided into eigth phenological stages. A micrometeorological tower was mounted in a grape-plants row in which sensors of net radiation, global solar radiation and wind speed were installed at about 1.0 m above the canopy. Also in the tower, two psicometers were installed at two levels (0.5 and 1.8 m) above the vineyard canopy. Two soil heat flux plates were buried at 0.02 m beneath the soil surface. All these sensors were connected to a Data logger 21 X of Campbell Scientific Inc., programmed for collecting data once every 5 seconds and storage averages for every 15 minutes. A comparative analysis were made among four Bowen ratio accepting/rejecting rules, according to the methodology proposed by Spano et al. (2000): betar1 - values of beta calculated by Bowen (1926) equation; betar2 - values of beta as proposed by Verma et al. (1978) equation; betar3 - exclusion of the beta values obtained as recommended by Unland et al. (1996) and betar4 - exclusion of the beta values calculated as proposed by Bowen (1926), out of the interval (-0.7 < beta < 0.7). Constacted that the Unland et al. (1996) and Soares (2003) accepting/rejection rules were better than that of Verma et al. (1978) for attenuating the advective effects on the calculations of the Bowen ratio. The comparison of betar1 with betar2 rules showed that the statistical errors reaching maximum values of 0.015. When comparing betar1 with betar3 e betar4, the beta errors reaching maximum values of 5.80 and 3.15, respectively.

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