scholarly journals Micrometeorological methods to estimate sugarcane evapotranspiration in coastal northeastern region of Brazil

2019 ◽  
pp. 1422-1428
Author(s):  
Adolpho Emanuel Quintela da Rocha ◽  
José Leonaldo de Souza ◽  
Guilherme Bastos Lyra ◽  
Ricardo Araújo Ferreira Junior ◽  
Gustavo Bastos Lyra ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Bowen Ratio ◽  
Water Vapour Pressure ◽  
Sensible Heat ◽  
Energy Balance Method ◽  
Ratio Energy

The aim of the present work was to evaluate the performance of Bowen ratio-energy balance method, as well as the energy balance closure by Eddy covariance technique for a sugarcane crop in Brazilian northeastern region. Micrometeorological measurements were carried out between June 7th and November 17th, 2013. Latent and sensible heat fluxes were determined through Eddy covariance technique (EC) and by the Bowen ratio-energy balance method (BREB), considering two approaches. The first, estimated the air temperature and water vapour pressure gradient in two levels above the canopy. The second method measured the air temperature and water vapour pressure at the first level and the surface temperature from radiometric measurements. Latent heat flux was also estimated as energy balance residue from determinations of the sensible heat flux by Eddy covariance. The degree of energy balance closure was dependent on the time of the day considered. Bowen ratio - energy balance estimated from the first approach, showed the best agreement with the eddy covariance measurements to estimate latent heat flux, while in the second case, when the Bowen ratio was estimated using the surface temperature, the linear relationship was the most discrepant. Therefore, the Bowen ratio conventional method is more suitable for estimating latent heat flux in sugarcane.

scholarly journals Comparing Aircraft-Based Remotely Sensed Energy Balance Fluxes with Eddy Covariance Tower Data Using Heat Flux Source Area Functions

2005 ◽  
Vol 6 (6) ◽  
pp. 923-940 ◽  
Author(s):  
JoséL. Chávez ◽  
Christopher M. U. Neale ◽  
Lawrence E. Hipps ◽  
John H. Prueger ◽  
William P. Kustas
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Source Area ◽  
Soil Heat Flux ◽  
Sensible Heat ◽  
Atmospheric Conditions

Abstract In an effort to better evaluate distributed airborne remotely sensed sensible and latent heat flux estimates, two heat flux source area (footprint) models were applied to the imagery, and their pixel weighting/integrating functionality was investigated through statistical analysis. Soil heat flux and sensible heat flux models were calibrated. The latent heat flux was determined as a residual from the energy balance equation. The resulting raster images were integrated using the 2D footprints and were compared to eddy covariance energy balance flux measurements. The results show latent heat flux estimates (adjusted for closure) with errors of (mean ± std dev) −9.2 ± 39.4 W m−2, sensible heat flux estimate errors of 9.4 ± 28.3 W m−2, net radiation error of −4.8 ± 20.7 W m−2, and soil heat flux error of −0.5 ± 24.5 W m−2. This good agreement with measured values indicates that the adopted methodology for estimating the energy balance components, using high-resolution airborne multispectral imagery, is appropriate for modeling latent heat fluxes. The method worked well for the unstable atmospheric conditions of the study. The footprint weighting/integration models tested indicate that they perform better than simple pixel averages upwind from the flux stations. In particular the flux source area model (footprint) seemed to better integrate the resulting heat flux image pixels. It is suggested that future studies test the methodology for heterogeneous surfaces under stable atmospheric conditions.

scholarly journals Diurnal Energy Balance in a Mango Orchard in the Northeast of Pará, Brazil

2018 ◽  
Vol 33 (3) ◽  
pp. 537-546 ◽  
Author(s):  
Paulo Jorge de Oliveira Ponte de Souza ◽  
Juliana Chagas Rodrigues ◽  
Adriano Marlisom Leão de Sousa ◽  
Everaldo Barreiros de Souza
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Soil Cover ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Net Radiation ◽  
Growing Seasons ◽  
Available Energy

Abstract This study aimed to evaluate the diurnal energy balance during the reproductive stage of two growing seasons of a mango orchard in the northeast of Pará, Brazil. Therefore, a micrometeorological tower was installed and instrumented, in the center of the experimental area, to monitor meteorological variables, besides the phenological evaluation of the mango orchard, which was carried out during growing seasons of 2010-2011 (October 2010 to January 2011) and of 2011-2012 (September 2011 to January 2012). The energy balance was obtained by the bowen ration technique, and the available energy partitioned into heat flux to the ground, sensible heat and latent heat. The amount of rainfall was crucial to the partition of the net radiation in the energy balance components. It provided the variation in the consumption of available energy between 69% and 78% as latent heat flux, and between 23% and 32% as sensible heat flux. The heat flux to the ground was small, representing less than 1% of the net radiation, showing that the mango orchard exhibits good soil cover preventing large variations in soil heating.

Comparison of energy fluxes from eddy covariance and scintillometer over an agricultural field

2020 ◽  
Author(s):  
Matěj Orság ◽  
Milan Fischer ◽  
Josef Eitzinger ◽  
Miroslav Trnka
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Soil Heat Flux ◽  
Radiation Balance ◽  
Energy Balance Closure ◽  
Sensible Heat ◽  
Agricultural Field ◽  
Available Energy

<p>In this study we compare turbulent energy fluxes obtained from eddy covariance (EC) (LI-7500A, LI-COR + Windmaster, Gill Instruments) and large aperture scintillometer (BLS900, Scintec) over an agricultural field (wheat field, straw and bare soil). As the EC method provides direct measurements of sensible heat (H<sub>EC</sub>) and latent heat (LE<sub>EC</sub>) fluxes we use it as a reference method. The EC method enables to determine fluxes within a footprint centered around the point of measurement in the middle of the field. The scintillometer provides an estimation of sensible heat flux (H<sub>SC</sub>), derived from air refractive index fluctuation integrated over the measurement path length, in this case 570 m diagonally across whole field. The reference measurements of the radiation balance components consist of 4-component net radiometer for net radiation (Rn) (NR01, Hukseflux), three soil heat flux plates for soil heat flux (G) monitoring (HFP01, Hukseflux), including thermocouples for quantification of the heat storage above the soil heat flux plates. The scintillometer-based latent heat (LE<sub>SC</sub>) is calculated as a residuum from available energy (Rn-G) and H<sub>SC</sub>, provided by scintillometer. The measurement of radiation balance components was located at the top of 3.5 m mast with the EC system, while the soil heat flux plates were collocated around in 5 cm depth. The site is a flat, rectangular agricultural field (app. 16.5 ha), in the north-eastern Austria, Danube river lowland (48.21N, 16.622E), sown with winter wheat during growing season 2019. The measurement campaign was established in February 2019 with aim for multi-seasonal monitoring. The EC measurement height is 2.7 m, the scintillometer transmitter and receiver are fixed on 4 m masts, facing towards each other from NW and SE corners of the field.</p><p>Comparison of the EC-based turbulent fluxes (H<sub>EC</sub>+LE<sub>EC</sub>) and the available energy (Rn-G) during the period March to Mid-June showed a very good agreement, resulting in the energy balance closure of 0.96 (R<sup>2 </sup>= 0.93). This suggest high accuracy and robustness of the measurement setup together with the ability of the EC method to capture all scales of eddies responsible for energy transport at this site. The comparison of methods indicates that H<sub>SC</sub> overestimated H<sub>EC</sub> by 10 % (R<sup>2 </sup>= 0.74) and LE<sub>SC</sub> underestimated LE<sub>EC</sub> by 13 % (R<sup>2 </sup>= 0.81). Related to Rn, the H<sub>EC</sub>, LE<sub>EC</sub> and G fluxes accounted for 22 % (R<sup>2 </sup>= 0.53), 59 % (R<sup>2 </sup>= 0.70) and 15% (R<sup>2 </sup>= 0.62) of the Rn flux, respectively. We assume that the combination of EC and scintillometer method has a potential to bring deeper insight into the analysis of the energy balance closure problem.</p>

scholarly journals Energy balance in a renewal sugarcane area with fallow period and soybean cultivation

2020 ◽  
Vol 42 ◽  
pp. e39
Author(s):  
Rubmara Ketzer Oliveira ◽  
Luciano Sobral Fraga Junior ◽  
Larissa Brêtas Moura ◽  
Debora Regina Roberti ◽  
Felipe Gustavo Pilau
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Rainfall Regime ◽  
Sensible Heat ◽  
Energy Fluxes ◽  
Fallow Period

Brazil is the main sugarcane producer in the world, which is intended for various purposes, from food to power generation. Soybean cultivation in areas of sugarcane under renewal has been growing progressively in Brazil. Quantifying energy fluxes at different stages of this process is essential for better management. The work was carried out in Piracicaba city, with the objective of analyzing the behavior of energy fluxes and the closing of the energy balance in a sugarcane renewal area with a fallow period followed by soybean cultivation. The latent and sensitive heat fluxes were obtained with the “Eddy covariance” method. The closing of the energy balance in the fallow period with straw-covered uncovered and soybean-cultivated soil presented a correlation coefficient of 0.88, 0.78 and 0.71, respectively. In the period without cultivation, the sensible heat flux was predominant in relation to the latent heat flux, varying according to the rainfall regime. The presence of straw under the soil in the fallow period affected the latent heat flux. With soybean cultivation, the latent heat flux surpassed the sensible heat flux.

scholarly journals Permafrost and surface energy balance of a polygonal tundra site in Northern Siberia – Part 2: Winter

2010 ◽  
Vol 4 (3) ◽  
pp. 1391-1431 ◽  
Author(s):  
M. Langer ◽  
S. Westermann ◽  
S. Muster ◽  
K. Piel ◽  
J. Boike
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Surface Energy Balance ◽  
Radiation Budget ◽  
Sensible Heat ◽  
Northern Siberia ◽  
Ground Heat Flux

Abstract. Permafrost is largely determined by the surface energy balance. Its vulnerability to degradation due to climate warming depends on complex soil-atmosphere interactions. This article is the second part of a comprehensive surface energy balance study at a polygonal tundra site in Northern Siberia. It comprises two consecutive winter periods from October 2007 to May 2008 and from October 2008 to January 2009. The surface energy balance is obtained by independent measurements of the radiation budget, the sensible heat flux and the ground heat flux, whereas the latent heat flux is inferred from measurements of the atmospheric turbulence characteristics and a model approach. The measurements reveal that the long-wave radiation is the dominant factor in the surface energy balance. The radiative losses are balanced to about 60% by the ground heat flux and almost 40% by the sensible heat fluxes, whereas the contribution of the latent heat flux is found to be relatively small. The main controlling factors of the surface energy budget are the snow cover, the cloudiness and the soil temperature gradient. Significant spatial differences in the surface energy balance are observed between the tundra soils and a small pond. The heat flux released from the subsurface heat storage is by a factor of two increased at the freezing pond during the entire winter period, whereas differences in the radiation budget are only observed at the end of winter. Inter-annual differences in the surface energy balance are related to differences in snow depth, which substantially affect the temperature evolution at the investigated pond. The obtained results demonstrate the importance of the ground heat flux for the soil-atmosphere energy exchange and reveal high spatial and temporal variabilities in the subsurface heat budget during winter.

scholarly journals Application of the Flux-Variance Technique for Evapotranspiration Estimates in Three Types of Agricultural Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Ori Ahiman ◽  
Yonatan Mekhmandarov ◽  
Moran Pirkner ◽  
Josef Tanny
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Turbulent Transport ◽  
Control Analysis ◽  
Energy Balance Closure ◽  
Tomato Crop ◽  
Simple Method

Irrigation of protected crops requires sound knowledge of evapotranspiration. Previous studies have established that the eddy-covariance (EC) technique is suitable for whole canopy evapotranspiration measurements in large agricultural screenhouses. Nevertheless, the eddy-covariance technique remains difficult to apply in the farm due to costs, operational complexity, and postprocessing of data, thereby inviting alternative techniques to be developed. The subject of this paper is the evaluation of a turbulent transport technique, the flux variance (FV), whose instrumentation needs and operational demands are not as elaborate as the EC, to estimate evapotranspiration within large agricultural structures. Measurements were carried out in three types of agricultural structures: (i) a banana plantation in a light-shading (8%) screenhouse (S1), (ii) a pepper crop in an insect-proof (50-mesh) screenhouse (S2), and (iii) a tomato crop in a naturally ventilated greenhouse with a plastic roof and 50-mesh screened sidewalls (S3). Quality control analysis of the EC data showed that turbulence development and flow stationarity conditions in the three structures were suitable for flux measurements. However, within the insect-proof screenhouse (below the screen) and the plastic-covered greenhouse, R2 of the energy balance closure was poor; hence, the alternative simple method could not be used. Results showed that the FV technique was suitable for reliable estimates of ET in shading and insect-proof screenhouses with R2 of the regressions between FV latent heat flux and latent heat flux deduced from energy balance closure of 0.99 and 0.92 during validation for S1 and S2, respectively.

scholarly journals The surface energy balance in a cold-arid permafrost environment, Ladakh Himalaya, India

2020 ◽  
Author(s):  
John Mohd Wani ◽  
Renoj J. Thayyen ◽  
Chandra Shekhar Prasad Ojha ◽  
Stephan Gruber
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Surface Energy Balance ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Sensible Heat ◽  
The Alps

Abstract. Cryosphere of the cold-arid trans-Himalayan region is unique with its significant permafrost cover. While the information on the permafrost characteristics and its extent started emerging, the governing energy regimes of this cryosphere region is of particular interest. This paper present the results of Surface Energy Balance (SEB) studies carried out in the upper Ganglass catchment in the Ladakh region of India, which feed directly to the River Indus. The point SEB is estimated using the one-dimensional mode of GEOtop model from 1 September 2015 to 31 August 2017 at 4727 m a.s.l elevation. The model is evaluated using field monitored radiation components, snow depth variations and one-year near-surface ground temperatures and showed good agreement with the respective simulated values. The study site has an air temperature range of −23.7 to 18.1 °C with a mean annual average temperature (MAAT) of −2.5 and ground surface temperature range of −9.8 to 19.1 °C. For the study period, the surface energy balance characteristics of the cold-arid site show that the net radiation was the major component with mean value of 28.9 W m−2 followed by sensible heat flux (13.5 W m−2) and latent heat flux (12.8 W m−2), and the ground heat flux was equal to 0.4 W m−2. The partitioning of energy balance during the study period shows that 47 % of Rn was converted into H, 44 % into LE, 1 % into G and 7 % for melting of seasonal snow. Both the study years experienced distinctly different, low and high snow regime. Key differences due to this snow regime change in surface energy balance characteristics were observed during peak summer (July–August). The latent heat flux was higher (lower) during this period with 39 W m−2 (11 W m−2) during high (low) snow years. The study also shows that the sensible heat flux during the early summer season (May, June) of the high (low) snow was much smaller (higher) −3.4 W m−2 (36.1 W m−2). During the study period, snow cover builds up in the catchment initiated by the last week of December facilitating the ground cooling by almost three months (October to December) of sub-zero temperatures up to −20 °C providing a favourable environment for permafrost. It is observed that the Ladakh region have a very low relative humidity in the range of 43 % as compared to, e.g., ~ 70 % in the Alps facilitating lower incoming longwave radiation and strongly negative net longwave radiation averaging ~ −90 W m−2 compared to −40 W m−2 in the Alps. Hence, the high elevation cold-arid region land surfaces could be overall colder than the locations with more RH such as the Alps. Further, it is apprehended that high incoming shortwave radiation in the region may be facilitating enhanced cooling of wet valley bottom surfaces as a result of stronger evaporation.

scholarly journals Comparison of energy balance on Gangotri and Chhota Shigri Glaciers

2014 ◽  
Vol XL-8 ◽  
pp. 537-542
Author(s):  
G. Rastogi ◽  
Ajai
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Net Radiation ◽  
Chhota Shigri Glacier ◽  
Himalayan Glaciers ◽  
Gangotri Glacier

Surface energy balance of a glacier governs the physical processes taking place at the surface-atmosphere interface and connects ice ablation/accumulation to climate variability. To understand the response of Himalayan glaciers to climatic variability, a study was taken to formulate energy balance equation on two of the Indian Himalayan glaciers, one each from Indus and Ganga basins, which have different climatic and physiographic conditions. Study was carried out over Gangotri glacier (Ganga basin) and Chhota Shigri(CS) glacier from Chandra sub-basin (Indus basin). Gangotri glacier is one of the largest glaciers in the central Himalaya located in Uttarkashi District, Uttarakhand, India. Chhota Shigri glacier of Chandra sub-basin lies in Lahaul and Spiti valley of Himachal Pradesh. Energy balance components have been computed using inputs derived from satellite data, AWS (Automatic Weather Station) data and field measurements. Different components of energy balance computed are net radiation (includes net shortwave and net longwave radiation), sensible heat flux and latent heat flux. In this study comparison has been made for each of the above energy balance components as well as total energy for the above glaciers for the months of November and December, 2011. It is observed that net radiation in Gangotri glacier is higher by approximately 43 % in comparison to Chhota Shigri glacier; Sensible heat flux is lesser by 77 %; Latent heat flux is higher by 66 % in the month of November 2011. Comparison in the month of December shows that net radiation in Gangotri glacier is higher by approximately 22 % from Chhota Shigri glacier; Sensible heat flux is lesser by 90 %; Latent heat flux is higher by 3 %.Total energy received at the glacier surface and contributes for melting is estimated to be around 32 % higher in Gangotri than Chhota Shigri glacier in November, 2011 and 1.25 % higher in December, 2011. The overall results contribute towards higher melting rate in November and December, 2011 in Gangotri than Chhota Shigri glacier.

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