scholarly journals Simulation of Water Vapor and Near Infrared Radiation to Predict Vapor Pressure Deficit in a Greenhouse Using CFD

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1587
Author(s):  
Cruz Ernesto Aguilar-Rodríguez ◽  
Jorge Flores-Velázquez ◽  
Fernando Rojano ◽  
Hector Flores-Magdaleno ◽  
Enrique Rubiños Panta
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Mass Fraction ◽  
Natural Ventilation ◽  
Vapor Pressure Deficit ◽  
Near Infrared ◽  
Experimental Phase ◽  
Near Infrared Radiation ◽  
Local Climate ◽  
Computational Fluid Dynamics Cfd

Vapor pressure deficit (VPD) can be used as an indicator to schedule greenhouse irrigation. VPD can be estimated as a function of relative humidity (RH) and temperature (T). The objective of this work was to analyze spatial variation in VPD as an indicator of water stress influenced by concentration of water vapor and intensity of near infrared (NIR). The study was carried out in an empty three-span sawtooth greenhouse with natural ventilation under the local climate in Montecillo, Mexico; these findings established a base value to analyze greenhouse field conditions prior to the influence from a crop. The experimental phase consisted of recording data (3 February 2019–24 February 2019) on temperature, humidity, solar radiation, and wind speed, which were used for developing a model in computational fluid dynamics (CFD). Then, this model was used to estimate VPD, considering changes in mass fraction of water vapor and the intensity of NIR. Scenarios with 50, 70, and 90% external RH were evaluated. It was found that without a crop, temperature was not affected by the variation in the mass fraction of water vapor and the intensity of NIR in the simulated scenarios, each of which generated a thermal gradient within the range of 4 °C. When considering the scenario of 90% external RH, we found the best VPD range along the greenhouse (2–3 kPa) that would be a favorable field condition for crops. Differences between VPD with and without a crop can be used to estimate the water quantity needs for crop growth based on the climate variables examined in this study, where higher VPD values require more water for irrigation.

scholarly journals Water Vapor Pressure Deficit in Portugal and Implications for the Development of the Invasive African Citrus Psyllid Trioza erytreae

Insects ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 229 ◽  
Author(s):  
Paulo Eduardo Branco Paiva ◽  
Tânia Cota ◽  
Luís Neto ◽  
Celestino Soares ◽  
José Carlos Tomás ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Control Measures ◽  
Effective Control ◽  
First Instar ◽  
Trioza Erytreae ◽  
Water Vapor Pressure Deficit

African citrus psyllid (Trioza erytreae (Del Guercio)) is a vector insect of the bacterium Candidatus Liberibacter africanus, the putative causal agent of Huanglongbing, the most devastating citrus disease in the world. The insect was found on the island of Madeira in 1994 and in mainland Portugal in 2015. Present in the north and center of the country, it is a threat to Algarve, the main citrus-producing region. Trioza erytreae eggs and first instar nymphs are sensitive to the combination of high temperatures and low relative humidity. Daily maximum air temperature and minimum relative humidity data from 18 weather stations were used to calculate the water vapor pressure deficit (vpd) from 2004 to 2018 at various locations. Based on the mean vpd and the number of unfavorable days (vpd < 34.5 and vpd < 56 mbar) of two time periods (February to May and June to September), less favorable zones for T. erytreae were identified. The zones with thermal and water conditions like those observed in the Castelo Branco and Portalegre (Center), Beja (Alentejo), Alte, and Norinha (Algarve) stations showed climatic restrictions to the development of eggs and first instar nymphs of African citrus psyllid. Effective control measures, such as the introduction and mass release of Tamarixia dryi (Waterson), a specific parasitoid, and chemical control are necessary in favorable periods for T. erytreae development, such as in spring and in areas with limited or no climate restrictions.

Physical and visual properties of grape rachis as affected by water vapor pressure deficit

2011 ◽  
Vol 59 (1) ◽  
pp. 25-33 ◽  
Author(s):  
A. Lichter ◽  
T. Kaplunov ◽  
Y. Zutahy ◽  
A. Daus ◽  
V. Alchanatis ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Water Vapor Pressure Deficit ◽  
Visual Properties

scholarly journals Modeling the Response of Canopy Stomatal Conductance to Humidity

2009 ◽  
Vol 10 (2) ◽  
pp. 521-532 ◽  
Author(s):  
Shusen Wang ◽  
Yan Yang ◽  
Alexander P. Trishchenko ◽  
Alan G. Barr ◽  
T. A. Black ◽  
...  
Keyword(s):  
Water Vapor ◽  
Stomatal Conductance ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Power Function ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Nonlinear Function ◽  
Environmental Variable ◽  
Water Vapor Pressure Deficit

Abstract Humidity of air is a key environmental variable in controlling the stomatal conductance (g) of plant leaves. The stomatal conductance–humidity relationships employed in the Ball–Woodrow–Berry (BWB) model and the Leuning model have been widely used in the last decade. Results of independent evaluations of the two models vary greatly. In this study, the authors develop a new diagnostic parameter that is based on canopy water vapor and CO2 fluxes to assess the response of canopy g to humidity. Using eddy-covariance flux measurements at three boreal forest sites in Canada, they critically examine the performance of the BWB and the Leuning models. The results show that the BWB model, which employs a linear relationship between g and relative humidity (hs), leads to large underestimates of g when the air is wet. The Leuning model, which employs a nonlinear function of water vapor pressure deficit (Ds), reduced this bias, but it still could not adequately capture the significant increase of g under the wet conditions. New models are proposed to improve the prediction of canopy g to humidity. The best performance was obtained by the model that employs a power function of Ds, followed by the model that employs a power function of relative humidity deficit (1 − hs). The results also indicate that models based on water vapor pressure deficit generally performed better than those based on relative humidity. This is consistent with the hypothesis that the stomatal aperture responds to leaf water loss because water vapor pressure deficit rather than relative humidity directly affects the transpiration rate of canopy leaves.

Hydration Chamber for Jeolco 200 Kv Microscope

1970 ◽  
Vol 28 ◽  
pp. 542-543
Author(s):  
V. R. Matricardi ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscope ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Room Temperature ◽  
List Type ◽  
Type Number ◽  
Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

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