scholarly journals Micrometeorological methods for inferring whole canopy evapotranspiration in large agricultural structures: measurements and modeling

2015 ◽  
Author(s):  
Josef Tanny ◽  
Gabriel Katul ◽  
Shabtai Cohen ◽  
Meir Teitel
Keyword(s):  
Eddy Covariance ◽  
Field Experiments ◽  
Turbulent Transport ◽  
Time Derivative ◽  
Theoretical Models ◽  
Alternative Methods ◽  
Control Analysis ◽  
Model Calculations ◽  
Canopy Volume ◽  
First Time

Original objectives and revisions The original objectives as stated in the approved proposal were: (1) To establish guidelines for the use of micrometeorological techniques as accurate, reliable and low-cost tools for continuous monitoring of whole canopy ET of common crops grown in large agricultural structures. (2) To adapt existing methods for protected cultivation environments. (3) To combine previously derived theoretical models of air flow and scalar fluxes in large agricultural structures (an outcome of our previous BARD project) with ET data derived from application of turbulent transport techniques for different crops and structure types. All the objectives have been successfully addressed. The study was focused on both screenhouses and naturally ventilated greenhouses, and all proposed methods were examined.  Background to the topic Our previous BARD project 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 post-processing of data – thereby inviting alternative techniques to be developed. The subject of this project was: 1) the evaluation of four turbulent transport (TT) techniques, namely, Surface Renewal (SR), Flux-Variance (FV), Half-order Time Derivative (HTD) and Bowen Ratio (BR), whose instrumentation needs and operational demands are not as elaborate as the EC, to estimate evapotranspiration within large agricultural structures; and 2) the development of mathematical models able to predict water savings and account for the external environmental conditions, physiological properties of the plant, and structure properties as well as to evaluate the necessary micrometeorological conditions for utilizing the above turbulent transfer methods in such protected environments.  Major conclusions and achievements The major conclusions are: (i) the SR and FV techniques were suitable for reliable estimates of ET in shading and insect-proof screenhouses; (ii) The BR technique was reliable in shading screenhouses; (iii) HTD provided reasonable results in the shading and insect proof screenhouses; (iv) Quality control analysis of the EC method showed that conditions in the shading and insect proof screenhouses were reasonable for flux measurements. However, in the plastic covered greenhouse energy balance closure was poor. Therefore, the alternative methods could not be analyzed in the greenhouse; (v) A multi-layered flux footprint model was developed for a ‘generic’ crop canopy situated within a protected environment such as a large screenhouse. The new model accounts for the vertically distributed sources and sinks within the canopy volume as well as for modifications introduced by the screen on the flow field and microenvironment. The effect of the screen on fetch as a function of its relative height above the canopy is then studied for the first time and compared to the case where the screen is absent. The model calculations agreed with field experiments based on EC measurements from two screenhouse experiments.  Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of four simple TT techniques for ET estimates within large agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable the future development of lowcost ET monitoring system which will be attainable for day-to-day use by growers in improving irrigation management.

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 Application of Turbulent Transport Techniques for Quantifying Whole Canopy Evapotranspiration in Large Agricultural Structures: Measurement and Theory

2011 ◽  
Author(s):  
Josef Tanny ◽  
Gabriel Katul ◽  
Shabtai Cohen ◽  
Meir Teitel
Keyword(s):  
Eddy Covariance ◽  
Water Use ◽  
Turbulent Transport ◽  
Flow Characteristics ◽  
Theoretical Models ◽  
Irrigation Scheduling ◽  
Crop Water ◽  
Eddy Covariance Technique ◽  
Scalar Fluxes ◽  
Wide Range

Original objectives and revisions The original objectives of this research, as stated in the approved proposal were: 1. To establish guidelines for the use of turbulent transport techniques as accurate and reliable tool for continuous measurements of whole canopy ET and other scalar fluxes (e.g. heat and CO2) in large agricultural structures. 2. To conduct a detailed experimental study of flow patterns and turbulence characteristics in agricultural structures. 3. To derive theoretical models of air flow and scalar fluxes in agricultural structures that can guide the interpretation of TT measurements for a wide range of conditions. All the objectives have been successfully addressed within the project. The only modification was that the study focused on screenhouses only, while it was originally planned to study large greenhouses as well. This was decided due to the large amount of field and theoretical work required to meet the objectives within screenhouses. Background In agricultural structures such as screenhouses and greenhouses, evapotranspiration (ET) is currently measured using lysimeters or sap flow gauges. These measurements provide ET estimates at the single-plant scale that must then be extrapolated, often statistically or empirically, to the whole canopy for irrigation scheduling purposes. On the other hand, turbulent transport techniques, like the eddy covariance, have become the standard for measuring whole canopy evapotranspiration in the open, but their applicability to agricultural structures has not yet been established. The subject of this project is the application of turbulent transport techniques to estimate ET for irrigation scheduling within large agricultural structures. Major conclusions and achievements The major conclusions of this project are: (i) the eddy covariance technique is suitable for reliable measurements of scalar fluxes (e.g., evapotranspiration, sensible heat, CO2) in most types of large screenhouses under all climatic conditions tested. All studies resulted with fair energy balance closures; (ii) comparison between measurements and theory show that the model is capable in reliably predicting the turbulent flow characteristics and surface fluxes within screenhouses; (iii) flow characteristics within the screenhouse, like flux-variance similarity and turbulence intensity were valid for the application of the eddy covariance technique in screenhouses of relatively dilute screens used for moderate shading and wind breaking. In more dense screens, usually used for insect exclusions, development of turbulent conditions was marginal; (iv) installation of the sensors requires that the system’s footprint will be within the limits of the screenhouse under study, as is the case in the open. A footprint model available in the literature was found to be reliable in assessing the footprint under screenhouse conditions. Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of the eddy covariance technique for flux measurements within agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable more accurate assessments of crop water use which may lead to improved crop water management and increased water use efficiency of screenhouse crops.

Isopotential points in square-wave voltammetry of reversible electrode reactions

2009 ◽  
Vol 74 (10) ◽  
pp. 1489-1501 ◽  
Author(s):  
Marina Zelić ◽  
Milivoj Lovrić
Keyword(s):  
Square Wave Voltammetry ◽  
Electrode Reaction ◽  
Time Model ◽  
Model Calculations ◽  
Square Wave ◽  
Electrode Reactions ◽  
Wave Voltammetry ◽  
Electron Transfer Processes ◽  
Diagnostic Criterion ◽  
First Time

Isopotential points in square-wave voltammetry are described for the first time. Model calculations and real measurements (performed with UO22+ and Eu3+ in perchlorate and bromide solutions, respectively) indicate that such an intersection could be observed when backward components of the net response, resulting from an increase in frequency or reactant concentration, are presented together. The electrode reaction should be fully reversible because quasireversible or slower electron transfer processes give the isopoints only at increasing reactant concentrations but not at increasing square-wave frequencies. The effect could be used as an additional diagnostic criterion for recognition of reversible electrode reactions where products remain dissolved in the electrolyte solution.

scholarly journals Applications of Chemically Modified Clay Minerals and Clays to Water Purification and Slow Release Formulations of Herbicides

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 9
Author(s):  
Tomas Undabeytia ◽  
Uri Shuali ◽  
Shlomo Nir ◽  
Baruch Rubin
Keyword(s):  
Clay Minerals ◽  
Field Experiments ◽  
Slow Release ◽  
Freeze Fracture ◽  
Nano Particles ◽  
Organic Cations ◽  
Small Scale ◽  
High Exposure ◽  
Model Calculations ◽  
Slow Release Formulations

This review deals with modification of montmorillonite and other clay-minerals and clays by interacting them with organic cations, for producing slow release formulations of herbicides, and efficient removal of pollutants from water by filtration. Elaboration is on incorporating initially the organic cations in micelles and liposomes, then producing complexes denoted micelle- or liposome-clay nano-particles. The material characteristics (XRD, Freeze-fracture electron microscopy, adsorption) of the micelle– or liposome–clay complexes are different from those of a complex of the same composition (organo-clay), which is formed by interaction of monomers of the surfactant with the clay-mineral, or clay. The resulting complexes have a large surface area per weight; they include large hydrophobic parts and (in many cases) have excess of a positive charge. The organo-clays formed by preadsorbing organic cations with long alkyl chains were also addressed for adsorption and slow release of herbicides. Another examined approach includes “adsorptive” clays modified by small quaternary cations, in which the adsorbed organic cation may open the clay layers, and consequently yield a high exposure of the siloxane surface for adsorption of organic compounds. Small scale and field experiments demonstrated that slow release formulations of herbicides prepared by the new complexes enabled reduced contamination of ground water due to leaching, and exhibited enhanced herbicidal activity. Pollutants removed efficiently from water by the new complexes include (i) hydrophobic and anionic organic molecules, such as herbicides, dissolved organic matter; pharmaceuticals, such as antibiotics and non-steroidal drugs; (ii) inorganic anions, e.g., perchlorate and (iii) microorganisms, such as bacteria, including cyanobacteria (and their toxins). Model calculations of adsorption and kinetics of filtration, and estimation of capacities accompany the survey of results and their discussion.

scholarly journals Preserving the variance in imputed eddy-covariance measurements: Alternative methods for defensible gap filling

2017 ◽  
Vol 232 ◽  
pp. 635-649 ◽  
Author(s):  
Sujit Kunwor ◽  
Gregory Starr ◽  
Henry W. Loescher ◽  
Christina L. Staudhammer
Keyword(s):  
Eddy Covariance ◽  
Alternative Methods ◽  
Gap Filling ◽  
Eddy Covariance Measurements

scholarly journals Comprehensive Metabolomics Study of Traditionally Important Rumex Species Found in Western Himalayan Region

2018 ◽  
Vol 13 (2) ◽  
pp. 1934578X1801300
Author(s):  
Ritika Sharma ◽  
Rupali Jandrotia ◽  
Bikram Singh ◽  
Upendra Sharma ◽  
Dinesh Kumar
Keyword(s):  
Raw Materials ◽  
Chemical Diversity ◽  
Control Analysis ◽  
Limit Of Quantification ◽  
Western Himalayan Region ◽  
Biological Potential ◽  
Metabolomics Study ◽  
Comprehensive Metabolomics ◽  
First Time ◽  
Concurrent Estimation

Rumex species are traditionally known to cure constipation, pain, inflammation, ulcer and tumor. The biological potential of Rumex nepalens is lies in chemical diversity of its constituents. In the present study, UPLC-DAD-MS method was developed for the concurrent estimation of polyphenols in Rumex species ( R. nepalensis, R. hastatus and R. dentatus) and validated for linearity (r2 > 0.999), limit of quantification and detection, inter and intraday precession, stabilities and recovery. The developed method has also been employed for metabolomic analysis of Rumex species. Qualitative and quantitative variation of polyphenols was observed among the aerial and root parts of Rumex species with highest content of polyphenol detected in aerial part of R. nepalensis. The quantitative data based matrix and HCA plot represents the variation of metabolites among the samples. R. nepalensis being widely used in traditional practices, was incorporated in detail. A total of seven molecules were isolated and characterized among which three compounds viz. 3- O- methyl epicatechin, quercetin-3- O- β-D-glucuronide and β-sitosterol-3- O- β-D-glucoside were isolated for first time from this plant. Eighteen metabolites were profiled in R. nepalensis using UPLC-MS/MS technique. Current comprehensive metabolomics approach will surely help in understanding the chemical diversity, discriminations and quality control analysis of raw materials and furnished products of Rumex.

Fatigue Damage From High Mode Number Vortex-Induced Vibration

2006 ◽  
Author(s):  
J. Kim Vandiver ◽  
Susan B. Swithenbank ◽  
Vivek Jaiswal ◽  
Vikas Jhingran
Keyword(s):  
Fatigue Damage ◽  
Field Experiments ◽  
Higher Harmonics ◽  
Vortex Induced Vibration ◽  
Third Harmonic ◽  
The Third ◽  
Damage Rate ◽  
Surface Vessels ◽  
Vortex Shedding Frequency ◽  
First Time

This paper presents results from two field experiments using long flexible cylinders, suspended vertically from surface vessels. The experiments were designed to investigate vortex-induced vibration (VIV) at higher than tenth mode in uniform and sheared flows. The results of both experiments revealed significant vibration energy at the expected Strouhal frequency (referred to in this paper as the fundamental frequency) and also at two and three times the Strouhal frequency. Although higher harmonics have been reported before, this was the first time that the contribution to fatigue damage, resulting from the third harmonic, could be estimated with some certainty. This was enabled by the direct measurement of closely spaced strain gauges in one of the experiments. In some circumstances the largest RMS stress and fatigue damage due to VIV are caused by these higher harmonics. The total fatigue damage rate including the third harmonic is shown to be up to forty times greater than the damage rate due to the vibration at the fundamental vortex-shedding frequency alone. This dramatic increase in damage rate due to the third harmonic appears to be associated with a narrow range of reduced velocities in regions of the pipe associated with significant flow-induced excitation.

scholarly journals Consumer Preferences for Oyster Attributes: Field Experiments on Brand, Locality, and Growing Method

2017 ◽  
Vol 46 (2) ◽  
pp. 315-337 ◽  
Author(s):  
Maik Kecinski ◽  
Kent D. Messer ◽  
Lauren Knapp ◽  
Yosef Shirazi
Keyword(s):  
United States ◽  
Field Experiments ◽  
Consumer Preferences ◽  
Revealed Preference ◽  
The United States ◽  
Dichotomous Choice ◽  
Production Methods ◽  
The Past ◽  
Oyster Aquaculture ◽  
First Time

Oyster aquaculture has experienced tremendous growth in the United States over the past decade, but little is known about consumer preferences for oysters. This study analyzed preferences for oysters with varied combinations of brands, production locations, and production methods (aquaculture vs. wild-caught) using dichotomous choice, revealed preference economic field experiments. Results suggest significant and distinct differences in behavior between first-time and regular oyster consumers. While infrequent oyster consumers were drawn to oysters labeled as wild-caught, experienced oyster consumers preferred oysters raised via aquaculture. These findings will be valuable for growers and policymakers who invest in aquaculture to improve surrounding ecosystems.

scholarly journals On the relationship between acetone and carbon monoxide in air masses of different origin

2003 ◽  
Vol 3 (1) ◽  
pp. 1017-1049
Author(s):  
M. de Reus ◽  
H. Fischer ◽  
F. Arnold ◽  
J. de Gouw ◽  
R. Holzinger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Field Experiments ◽  
Marine Boundary Layer ◽  
Biogenic Emissions ◽  
Model Calculations ◽  
Single Observation ◽  
Tropical Regions ◽  
Air Masses ◽  
Clean Air

Abstract. Carbon monoxide and acetone measurements are presented for five aircraft measurement campaigns at mid-latitudes, polar and tropical regions in the northern hemisphere. Throughout all campaigns, free tropospheric air masses, which were influenced by anthropogenic emissions, showed a similar linear relation between CO and acetone, with a slope of 21–25 pptv acetone/ppbv CO. Measurements in the anthropogenically influenced marine boundary layer revealed a slope of 13–16 pptv acetone/ppbv CO. The different slopes observed in the marine boundary layer and the free troposphere indicate that acetone is emitted by the ocean in relatively clean air masses and taken up by the ocean in polluted air masses. In the lowermost stratosphere, a good correlation between CO and acetone was observed as well, however, with a much smaller slope (~5 pptv acetone/ppbv CO) compared to the troposphere. This is caused by the longer photochemical lifetime of CO compared to acetone in the lower stratosphere, due to the increasing photolytic loss of acetone and the decreasing OH concentration with altitude. No significant correlation between CO and acetone was observed over the tropical rain forest due to the large direct and indirect biogenic emissions of acetone. The common slopes of the linear acetone-CO relation in various layers of the atmosphere, during five field experiments, makes them useful for model calculations. Often a single observation of the CO-acetone correlation, determined from stratospheric measurements, has been used in box model applications. This study shows that different slopes have to be considered for marine boundary layer, free tropospheric and stratospheric air masses, and that the CO-acetone relation cannot be used for air masses which are strongly influenced by biogenic emissions.

scholarly journals Interannual, summer, and diel variability of CH4 and CO2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010–2015

2020 ◽  
Author(s):  
Werner Eugster ◽  
Tonya DelSontro ◽  
Gaius R. Shaver ◽  
George W. Kling
Keyword(s):  
Eddy Covariance ◽  
Diel Variability ◽  
First Time ◽  
Toolik Lake

CH4 and CO2 fluxes from Toolik Lake obtained for the first time with eddy covariance during ice-free periods 2010–2015.

Sign in / Sign up

Export Citation Format

Share Document