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Principles of Environmental Physics
Abstract
PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX
... z 0m can be determined by acquiring surface physical factors through observations (Monteith, 1973;Nicholas and Lewis, 1980;Shaw and Pereira, 1982;Colin, 2010;Zhang et al., 2004;Nakai et al., 2008;Liu et al., 2016;Chu et al., 2018). In practical applications, particularly for pixel-scale remote sensing estimation models, it is difficult to estimate the heterogeneous surface roughness heights. ...
... Within a plant canopy G 0 is modeled as an exponential extinction function of R n (Monteith, 1973). A simple exponential decay conceptual model (Choudhury et al., 1986(Choudhury et al., , 1987Kustas et al., 1993) is used to build exponential decay relationships over a wide variety of land surface: ...
... where C is the coefficient of Γ for the bare soil coefficient; τ is the extinction coefficient, which varies with vegetation type and solar zenith angle (Monteith, 1973). Hereby considering the particularity of permafrost absorbing and releasing heat and plateau vegetation in the study area, an adjusted scheme of stratified classification estimation based on LAI and DEM data is adopted. ...
Land surface temperature (LST) derived from satellite thermal infrared (TIR) remote sensing is widely used in estimating land surface evapotranspiration (ET) through energy balance theory. However, as satellite TIR remote sensing is frequently affected by clouds, the derived LST with spatial missing makes it impossible to estimate seamless ET for large areas. In this study, based on the all-weather LST (AWLST) generated through the synergistic use of TIR and passive microwave (PMW) remote sensing, we propose an estimation scheme of all-weather ET (AWET) for the River Source Region of Southwest China (RSR-SC) with complex environmental characteristics of frequent clouds and fog. Specifically, the parameters of the Surface Energy Balance System (SEBS), which have high impact on the model results, are first accurately determined by a global sensitivity analysis. Second, the parametric calculation schemes of turbulent exchange, such as surface roughness heights for momentum (z0m) and heat (z0h) transfer, and soil heat flux (G0) of the SEBS model are refined. Third, the daily ET temporal upscaling method is developed. Then a long-term AWET product for the RSR-SC is generated. Comparison against ground measurements from 12 eddy covariance (EC) sites indicates a good accuracy of the AWET product: the mean absolute percent error (MAPE) and root mean square error (RMSE) of the daily ET estimates are 36% and 0.88 mm/d, respectively. From aspects of temporal variation of daily ET, monthly spatiotemporal distribution patterns, interannual variation of different land covers and spatial distribution comparison with other ET products, the generated AWET exhibits to be realistic, reflecting relatively subtle variations. Further investigation indicates that the response of surface ET to the warming temperatures exhibits the spatial heterogeneity of the change trend. This study highlights the importance of estimating daily AWET at a MODIS-like scale using AWLST data to significantly benefit water resource monitoring and conduct runoff prediction over large areas and watershed scales.
... The [27] general light extinction model was initially developed using an ellipsoidal inclination angle distribution for plant leaves based on the following assumptions: kp represents the ratio between the projected horizontal shadow cast and the leaf area [77]. The leaf area distribution of most vegetated canopies can have a spherical, cylindrical, or conical shape [78]. ...
... The [27] general light extinction model was initially developed using an ellipsoidal inclination angle distribution for plant leaves based on the following assumptions: k p represents the ratio between the projected horizontal shadow cast and the leaf area [77]. The leaf area distribution of most vegetated canopies can have a spherical, cylindrical, or conical shape [78]. ...
This study focused on developing a novel semi-empirical model for maize’s light extinction coefficient (kp) by integrating multiple remotely sensed vegetation features from several different remote sensing platforms. The proposed kp model’s performance was independently evaluated using Campbell’s (1986) original and simplified kp approaches. The Limited Irrigation Research Farm (LIRF) in Greeley, Colorado, and the Irrigation Innovation Consortium (IIC) in Fort Collins, Colorado, USA, served as experimental sites for developing and evaluating the novel maize kp model. Data collection involved multiple remote sensing platforms, including Landsat-8, Sentinel-2, Planet CubeSat, a Multispectral Handheld Radiometer, and an unmanned aerial system (UAS). Ground measurements of leaf area index (LAI) and fractional vegetation canopy cover (fc) were included. The study evaluated the novel kp model through a comprehensive analysis using statistical error metrics and Sobol global sensitivity indices to assess the performance and sensitivity of the models developed for predicting maize kp. Results indicated that the novel kp model showed strong statistical regression fitting results with a coefficient of determination or R2 of 0.95. Individual remote sensor analysis confirmed consistent regression calibration results among Landsat-8, Sentinel-2, Planet CubeSat, the MSR, and UAS. A comparison with Campbell’s (1986) kp models reveals a 44% improvement in accuracy. A global sensitivity analysis identified the role of the normalized difference vegetation index (NDVI) as a critical input variable to predict kp across sensors, emphasizing the model’s robustness and potential practical environmental applications. Further research should address sensor-specific variations and expand the kp model’s applicability to a diverse set of environmental and microclimate conditions.
... According to the Penman-Monteith equation [39], the latent heat flux density (λE) depends on the available energy (F A ), the water vapour pressure deficit (D), the aerodynamic resistance (r a ), the surface resistance (r c ), the thermodynamic psychrometric constant (γ), the density of the air (ρ) and the rate of change of the saturated vapour pressure with temperature (∆): ...
... β was proved to be 0.554. Surface resistance (r c ) can be composed of the response functions of minimum surface resistance, solar radiation, water vapor pressure deficit, atmospheric temperature and soil water capacity [39,40]. The response functions of solar radiation and water vapor pressure deficit can be defined as hyperbolic function and inverse proportional function, respectively [22,41]. ...
Wetlands, which are composed of soil, vegetation and water, have sufficient water supply and are sensitive to climate change. This study analyzes the coupling degree between wetlands and atmosphere and discusses the influence of environmental factors (solar radiation and water vapor pressure deficit) on latent heat flux by using the experimental data from the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS and WRF models. The results showed that, during the vegetation growing season, the average value of Ω (decoupling factor) is 0.38 in alpine wetlands, indicating that the coupling between wetlands and atmosphere is poor. Solar radiation is the main factor influencing the latent heat flux in the results of both observation data analysis and model simulation, and solar radiation and water vapor pressure deficit still have the opposite reaction to latent heat flux; when solar radiation increased by 30%, the average daily amount of latent heat flux increased from 5.57 MJ·m−2 to 7.50 MJ·m−2; when water vapor pressure deficit increased by 30%, the average daily amount of latent heat flux decreased to 5.17 MJ·m−2. This study provides a new research approach for the study of the parameterization of latent heat flux and evapotranspiration in the context of global climate change
... From 0.7 μm, the absorption decreases drastically, reaching a minimum of 10% between 0.7 and 1.2 μm. From 1.2 μm, the absorption increases again, reaching values at 1.5, 2.1, and 2.5 μm (Monteith, 2013). In addition to optical properties, the transmission of radiation also depends on the canopy structure. ...
... Relationship between reflection, transmission, and absorption of a green leaf systematized. Source: Adapted fromMonteith (2013). ...
The importance of coffee crops in the global agricultural scenario goes beyond economic aspects, also encompassing political and sociocultural factors. Brazil stands out in this scenario as the largest producer and exporter of coffee in the world, with a particular emphasis on the state of Minas Gerais. Coffee production is mainly focused on the Coffea arabica L. species. However, several factors directly impact coffee crop productivity, resulting in significant losses. Among the most relevant factors are adverse climatic conditions, nutritional deficiencies, and the presence of pests and diseases. Therefore, it is essential to seek an efficient metabolic response from coffee crops in the face of biotic and abiotic stresses, developing plants that are more resistant to climate variations. Based on the literature, this review is structured as follows: first, the characteristics and growth habits of coffee crops are presented; second, 18 cultivars of Arabica coffee analyzed in the study are discussed, providing specific agronomic information for each of them; subsequently, the coffee’s phenological cycle and productivity are addressed; finally, radiometric variables such as photosynthetically active radiation (PAR), fraction of absorbed photosynthetically active radiation (f APAR ), transmittance, reflectance, and leaf area index (LAI) are treated. The evidence gathered in this review unanimously points to the need for intensified studies on solar radiation interception and LAI in different cultivars of Arabica coffee. The literature highlights the importance of using field-obtained datasets to complement information on the characteristics and growth patterns of varieties, as well as their phenological cycle, in order to understand the plant’s behavior before and after harvesting and its relation to productivity.
... Most of these models were developed for estimating evapotranspiration from measured climatic data. In our case we used two methods for ET estimation: the Penman-Monteith Method (PM Method) [1,5,6,8] and the Bowen Ratio Method (BR Method) [7,9,13]. Both of these methods are based on the fact that the evaporation of water requires relatively large amounts of energy. ...
... Therefore the next consideration is restricted to daylight conditions. It holds [10] that Rn Rs Rl , (5) where Rs is the intensity of the net shortwave (solar) radiation and Rl is the intensity of the net longwave radiation between the earth and the atmosphere. The boundary between the shortwave and longwave radiation has a wavelength of 3 m. ...
Many hydrologic models and agricultural management applications require evapotranspiration estimates. The intensity of evapotranspiration is mainly determined by mathematical models rather than by direct measurement. In addition to its own estimate of evapotranspiration it is necessary to determine the uncertainty of this estimate. This uncertainty is not usually mentioned. In this paper these formulas are derived for the uncertainty estimate of evapotranspiration under simplifying assumptions. These assumptions enabled one to derive an expression of evapotranspiration estimation uncertainty suitable for practical applications. The paper focuses on both the absolute and the relative uncertainty of evapotranspiration estimation. The derived formulas can be used for determining the uncertainty in evapotranspiration estimation, but as well as for the accuracy estimate which is necessary for the measuring of input variables. The derived relationship shows that the net radiation should be more accurately measured than the other energy fluxes that have an influence on evapotranspiration. It follows that the relative uncertainty of evapotranspiration is primarily influenced by the relative uncertainty of net radiation. The uncertainty in the measurement of net radiation was derived from data obtained by using a radiometer which was equipped with a pair of pyranometers and with a pair of pyrgeometers. Planck’s Law was used for spectral analysis. The possible presence of systematic errors in the measuring of net radiation was evaluated for its potential impact on the errors of the evapotranspiration estimate. This paper is accompanied by measurement records and graphs documenting the achieved results.
... In the FAO-56 single crop coefficient approach, the effect of both crop transpiration and soil evaporation are integrated into a single crop coefficient (Kc). However, crop evapotranspiration (ETc) estimation is more accurate by dual crop coefficient approach than the single crop coefficient approach, the dual crop coefficient approach uses more parameters and take soil practices and crop characteristics into consideration [18,13,19]. In the dual approach a daily basal crop coefficient (Kcb), representing primarily the plant transpiration, and a daily soil evaporation coefficient (Ke) are considered separately according to the equation: ...
... d4= diameter of shaded area by cacao canopy (2m), A is per cent ground cover by cacao canopy; Tree spacing is 3x3 m (9 m 2 ); d1 (areal canopy area), d2 (height bt d1 and d3); d3 (projection of canopy area on ground, d1> d3). Canopy volume = (18) ...
The humid tropics is characterized by wet-dry seasonal transitions, irrigation has the potential for building adaptation and resilience to climate stress for enhancing crop performance. A field trial was conducted to investigate the effects of dry season irrigation regimes on water use, root zone moisture dynamics and yield of cacao in a rainforest zone of Nigeria. Irrigation amounts computed as EPan x Pan coefficients were based on cumulative class A Pan evaporation. Irrigation treatments were coded as IrT1 (EPan x 1,0), IrT2 (EPan x 0.7) and IrT3 (EPan x 0.5). Irrigation water was applied 5-days interval and discharged via point source emitters (2.8 l/h discharge rate ) on drip lines laterally installed per row of trees. Mean irrigation requirements were 4.49 mm (9.81:9.6 l/tree/day), 3.14 mm (7.06:6.8 l/tree/day) and 2.44 mm (5.49: 4.8 l/tree/day) while total seasonal water applied were 121.19, 84.83 and 60.59 l/tree for IrT1, IrT2 and IrT3 respectively. Mean soil moisture contents and cacao evapotranspiration (ETc) were 52, 45 and 28 % and 4.54, 3.19 and 2.32 mm/day while evaporation from soil area wetted by emitters (EWz) were 5.65, 2.82 and 0.19 mm/day for respective IrT1, IrT2 and IrT3. The deficit irrigation strategies (IrT2 and 31 IrT3) imposed soil moisture deficit stress on cacao and produced lower pod and bean yields, it however enhanced water use efficiencies (25 and 44 %) and 30 and 50 % water savings. The study established suitable Pan coefficients for scheduling irrigation for cacao yield enhancement and drought (climate stress) amelioration.
... A number of plant tissue attributes vary along a vertical gradient within a crop stand. This has major consequences on epidemics caused by aerially dispersed pathogens: (1) leaf tissues at the base of the canopy have been exposed for a longer time to inoculum, compared to the newly formed leaves of the canopy top; (2) a crop canopy generates its own microclimate (Monteith 1973;Zadoks and Schein 1979), which is more humid, with reduced daily temperature variation, reduced wind speed and turbulences; (3) in dicot crops, upper canopy leaves often are smaller than older leaves at the base of the canopy, which in turn enables higher, very effective, auto-infections (Willocquet and Savary 2004); and (4) tissue susceptibility may vary (as, e.g., in groundnut;Savary 1987). ...
... Large-sized, non-overlapping leaves intercept the incoming radiation. Because radiation is the driving variable for other weather elements, microclimate within the canopy is modified in the course of the day and over a growing season (Monteith 1973). As a result, the microclimatic environment of leaves near the ground remains comparatively dark with dampened diurnal variation in weather elements, as compared to the leaves at the top of the canopy. ...
... However, this figure refers to direct radiation only. Not only is diffuse sky radiation predominantly in the visible spectrum but diffuse radiation was found to be equal to or exceed direct radiation on a cloudless day at solar elevations less than 20 0 at Sutton Bonington, UK (Monteith, 1973). The visible fraction of total solar radiation during overcast conditions (a typical occurrence during the Spitsbergen active season) tends to be slightly greater than during cloudless conditions. ...
... The visible fraction of total solar radiation during overcast conditions (a typical occurrence during the Spitsbergen active season) tends to be slightly greater than during cloudless conditions. Such considerations imply that the visible fraction of the total beam (and hence the photosynthetically active radiation (PAR)) at high arctic sites may exceed the 50 per cent derived by Monteith (1973). ...
The Thesis encompasses many aspects of the Micrometeorology of a Polar Desert site on the island of Svalbard with particular attention to the seminal eddy correlation measurements of CO2 during 2 spring-summer-autumn seasons and how the snow free seasonal extent affects the carbon balance.
... The snow melting process was calculated by the temperature-index method [30]. The evapotranspiration values of the surface soil, soil, and water were calculated using the Penman formula [31]. Evaporation from the vegetation canopy was calculated using the Penman-Monteith formula [31]. ...
... The evapotranspiration values of the surface soil, soil, and water were calculated using the Penman formula [31]. Evaporation from the vegetation canopy was calculated using the Penman-Monteith formula [31]. Infiltration was calculated on the basis of the rainfall intensity and using the Green-Ampt model or the Richards equation [32]. ...
Climate change alters hydrological processes in cold regions. However, the mechanisms of runoff component variation remain obscure. We implemented a WEP-N model to estimate monthly runoff in the Songhua River Basin (SRB) between 1956 and 2018. All flow simulations were accurate (NSE > 0.75 and RE < 5%). The annual runoff was attenuated in 1998, and the hydrological series (1956–2018) was divided into base and change periods in that year. Relative to the BS (base scenario), annual production flow reduction was −28.2% under climate change and water use. A multifactor attribution analysis showed that climate change and water use contributed 77.0% and 23.0% to annual runoff reduction, respectively. Decreases in annual surface and base flow explained 62.1% and 35.7% of annual production flow reduction, respectively. The base flow increased by 8.5% and 6.5% during the freezing and thawing periods, respectively. Relative to the BS, groundwater recharge increased by 9.2% and 4.1% during the freezing and thawing periods, respectively, under climate change conditions. Climate change was the dominant factor attenuating production flow. The change in production flow occurred mainly during the non-freeze-thaw period. The decrease in total production flow in the SRB was caused mainly by the decrease in the surface flow, where the reduction in base flow accounted for a relatively small proportion. Production flow attenuation aggravated water shortages. The utilization rate of groundwater resources is far below the internationally recognized alarm line. Therefore, attention should be directed towards certain areas of the SRB and other regions with minimal groundwater exploitation.
... It is expected that greater reflection would take place as the angle of incidence approaches 90° or grazing angle. 12 Muzzle is a hairless specialized portion of the integument. Its optical properties are determined by its surface and pigment layer. ...
This work aims to measure the total and spectral reflectance of visible radiation by various coat colors of cattle. It came to the interest of the author to determine also the reflectance by muzzle, a hairless pigmented portion of the integument. Measurement of the total and spectral reflectance of visible radiation, 400-700 nm, by cattle coat and muzzle was conducted using the integrating sphere and spectroradiometer. The total reflectance of visible radiation by black, brown and white coats were 77%, 11.68% and 65.76% respectively. Total reflectance values for muzzle were 11.5%, 34.61% and 22.l % for black, brown and brown-black muzzle respectively.
... Canopy conductance for water vapor (gcw) was calculated using the Penman-Monteith combination equation (Monteith 1973). The required values for the calculation were λΕ, Rn, S, and Δe measured by the BREB + system, and aerodynamic conductance. ...
In open fields, plants experience dynamic changes in environment, particularly radiation, temperature, wind, and humidity but their short-term responses have not been adequately characterized under natural conditions. In this study, we assessed causal effects of rapid radiation fluctuation on seven plant parameters in open fields of cotton and sweet corn canopies. The parameters are evapotranspiration (ET), canopy photosynthesis indicated by CO2 flux from air to canopy (FCO2), sensible heat energy flux (H), canopy conductance for water vapor (gcw), canopy surface temperature (Ts), shoot and leaf elongation rate, and stem diameter change. The energy and CO2 fluxes were measured with Bowen ratio/energy balance/CO2 gradient (BREB+) technique, using averaging time of 5 min. Shoot + leaf elongation and stem diameter change were monitored with position transducers using averaging time of 1 min. All parameters were all found to respond to change in radiation and transpiration within minutes or sooner. While radiation effects on canopy gas exchanges are expected, illuminating are the indirect but immediate effects on shoot + leaf growth and stem diameter change through radiation effects on transpiration and plant water status. A novel finding is that gcw also responded within minutes or sooner to radiation fluctuations and that FCO2 was related almost linearly to gcw. Results are discussed in terms of soil-plant-atmosphere continuum, and interpreted in terms of dynamic interactions between transpiration and plant water status. The clear inverse relationship between ET and elongation rate or stem diameter changes provides additional evidence supporting the validity of 5-min averaging for the BREB + technique.
... The reference crop evapotranspiration (ET 0 ) is calculated using the Penman-Monteith equation, reliant on meteorological data from proximate weather stations in the experimental vicinity. Then, the PET of the crop is subsequently calculated using the single crop coefficient method, followed by using the Beer's law to separate the potential evaporation and potential transpiration components [29]. ...
This study explores the impact of water and nitrogen management on the dynamics of water, heat, and nitrogen in farmland soil. It also explores the correlations soil factors, enzyme activity, and crop yield. To achieve this, field experiments and HYDRUS model simulations were conducted in the broad furrow irrigation system of the Yinhuang Irrigation Area. The experiment involved three irrigation levels (60%, 70%, and 80% of field water holding capacity, labeled as W1, W2, and W3, respectively) and three nitrogen application rates (120, 220, and 320 kg·ha−1, labeled as N1, N2, and N3). Results indicated that the HYDRUS model, optimized using field trial data, accurately represented soil dynamics. Soil profile water and nitrogen exhibited greater variation in the root zone (0–40 cm) than in the deeper layers (40–100 cm). Water–nitrogen coupling predominantly influenced water and nitrogen content changes in the soil, with minimal effect on soil temperature. Soil enzyme activities at the trumpet, silking, and maturity stages were significantly affected by water–nitrogen coupling, displaying an initial increase and subsequent decrease over the reproductive period. The highest summer maize yield, reaching 10,928.52 kg·ha−1 under the W2N2 treatment, was 46.64% higher than that under the W1N1 treatment. The redundancy analysis revealed a significant positive correlation between soil nitrate nitrogen content and soil enzyme activity (p < 0.05). Furthermore, there was a significant positive correlation between soil enzyme activity and both maize yields (p < 0.01). This underscores that appropriate water and nitrogen management can effectively enhance yield while improving the soil environment. These findings offer valuable insights for achieving high yields of summer maize in the Yellow River Basin.
... The main water and energy transfer processes of the model include evapotranspiration, runoff generation, confluence, and soil freeze-thaw processes. The Penman and Penman-Monteith equations were employed to characterize the evapotranspiration processes(Monteith, 1973;Penman, 1948). The Richards model was used to describe the movement of SM in unsaturated soils. ...
In order to increase the capability to understand and quantify the spatial differences in terrestrial water storage (TWS), and to reflect the unique energy balance processes and soil freeze–thaw mechanisms in the Qinghai‐Tibet Plateau (QTP), this study improved the energy balance processes of the water and energy transfer processes model, including its surface radiation calculations and snowmelt module. By integrating these improvements, a water and energy transfer processes model in Qinghai‐Tibet Plateau (WEP‐QTP) for the Yellow River source region (YRSR) is developed. Using the improved WEP‐QTP model to perform simulations, we assessed the daily changes in snow cover, soil moisture (SM), permafrost (PM), and groundwater storage (GWS) in the YRSR. Our analysis revealed an increase in TWS of 0.24 mm/yr from 1961 to 2020. Snow water equivalent (SWE), SM, PM, and GWS have proportional contributions of 8.33%, 216.67%, −154.17%, and 29.17% to the increased TWS, respectively. SM is the primary component of TWS. Temperature (T), precipitation (P), evapotranspiration (E), and solar radiation (Rs) influence the spatiotemporal variations in TWS, as well as those of its components. The increase in P is the primary cause for the rise in TWS, SWE, and SM, while the increase in T predominantly contributes to the decrease in PM. Furthermore, permafrost degradation and climate‐induced warming and humidification lead to increased infiltration, resulting in elevated GWS.
... The projected area of body parts (m 2 ) was calculated in the horizontal plane (i.e. ground shadow area) for cylinders after Monteith (1973) and cones after Pennell and Deignan (1989), for the corresponding solar zenith angle and an average azimuth angle of 45 deg for the numbat to the solar radiation. ...
We used thermal imagining and heat balance modelling to examine the thermal ecology of wild mammals, using the diurnal marsupial numbat (Myrmecobius fasciatus) as a model. Body surface temperature was measured using infra-red thermography at environmental wet and dry bulb temperatures of 11.7–29°C and 16.4–49.3°C, respectively; surface temperature varied for different body parts and with environmental temperature. Radiative and convective heat exchange varied markedly with environmental conditions and for various body surfaces reflecting their shapes, surface areas and projected areas. Both the anterior and posterior dorsolateral body areas functioned as thermal windows. Numbats in the shade had lower rates of solar radiative heat gain but non-solar avenues for radiative heat gain were substantial. Radiative gain was higher for black and lower for white stripes, but overall, the stripes had no thermal role. Total heat gain was generally positive (<4 to >20 W) and often greatly exceeded metabolic heat production (3–6 W). Our heat balance model indicates that high environmental heat loads limit foraging in open areas to as little as 10 min and that climate change may extend periods of inactivity, with implications for future conservation and management. We conclude that non-invasive thermal imaging is informative for modelling heat balance of free-living mammals.
... Penman first established an evaporation model based on an energy balance equation [46]. Then, Monteith enhanced the model by using aero-dynamic conductance, which depends not only on wind speed, but also on surface ruggedness, atmospheric stability, and vegetation height [47]. This modified model is known as the Penman-Monteith model. ...
The distributed Grid-Xin’anjiang (Grid-XAJ) model is very sensitive to the spatial and temporal distribution of data when used in humid and semi-humid small and medium catchments. We used the successive correction method to merge the gauged rainfall with rainfall forecasted by the Weather Research and Forecasting (WRF) model to enhance the spatiotemporal accuracy of rainfall distribution. And we used the Penman–Monteith equation to calculate the potential evapotranspiration (PEPM). Then, we designed two forcing scenarios (WRF-driven rainfall (Wr) + PEPM, WRF-merged rainfall (Wm) + PEPM) to drive the Grid-XAJ model for flood forecasting. We found the WRF-driven Grid-XAJ model held significant potential in flood forecasting. The Grid-XAJ model provided only an approximation of flood hygrographs when driven by scenario Wr + PEPM. The results in scenario Wm + PEPM showed a high degree-of-fit with observed floods with mean Nash–Sutcliffe efficiency coefficient (NSE) values of 0.94 and 0.68 in two catchments. Additionally, scenario Wm + PEPM performed better flood hygrographs than scenario Wr + PEPM. The flood volumes and flow peaks in scenario Wm + PEPM had an obvious improvement compare to scenario Wr + PEPM. Finally, we observed that the model exhibited superior performance in forecasting flood hydrographs, flow peaks, and flood volumes in humid catchments compared with semi-humid catchments.
... Leaf traits related to radiation loading and heat exchange impact leaf temperature. For example, optical traits, leaf size and orientation determine radiation loading (Jones and Rotenberg, 2011;Lambers et al., 1998), while material properties such as water content and density affect heat capacity (Jones, 2014;Lambers et al., 1998); leaf shape and area are related to heat conductance (g Ha ) (Leigh et al., 2012;Muller et al., 2021);Stomatal conductance (g s ) and water vapor transport conductance (g va ) influence transpirational cooling (Gates, 2003;Jones and Rotenberg, 2011;Monteith, 1973;Muir, 2019). However, it is challenging to study thermal effects of leaf traits in the field due to the high variability of leaf traits and their interactions Kitudom et al., 2022). ...
The ecophysiological processes of leaves are more related to leaf temperature (Tl) than air temperature (Ta). Transpiration and leaf physical traits enable plants to maintain Tl within a thermal range. However, it is challenging to quantitatively study leaf thermal regulation strategies, due to the complex interaction between thermal effects of transpiration and leaf physical traits. We utilized a 3-T method that compares Tl, Ta, and Tn (the temperature of non-transpiring leaves) investigate thermal regulation strategies of dominant canopy species in four vegetation types, including a savanna woodland, a tropical rain forest, a subtropical evergreen broad-leaved forest, and a temperate mixed forest. Our results indicate that the difference between Tl and Ta decreased as the site mean temperature increased. Transpirational cooling was strongest in savanna woodland, and decreased from the hottest site to the coldest site. Without transpiration, sun-exposed leaves were consistently hotter under sunshine than air. This physical warming effect increased from the hottest site to the coldest site. We observed leaf area, water content and leaf angle played a significant role in physical thermal regulation. The present research quantitatively measured leaf thermal regulation strategies across a temperature and precipitation gradient, which advances our understanding of how plants adapt to their thermal environments.
... Where; Rn is the net radiation (W/m 2 ), G is the heat flux below the canopy (W/m 2 ), cp is the heat capacity of air (J/kg°C) Monteith (1973) suggested that values of rcp and rcx could be obtained from measurements of stomatal resistance (ra) and leaf area index (LAI), where ...
This study addresses efficient water usage in wheat cultivation in a semi-arid region of India with clay loam soil and an increasing water supply-demand gap. It focuses on optimizing drip irrigation (DI) scheduling, of wheat crops, based on canopy air temperature difference (CATD) using the crop water stress index (CWSI). The field experiments were conducted for two winter seasons, employing high-discharge drip irrigation (DI) on wheat crop (variety - GW 366) at Junagadh Agricultural University (JAU), Gujarat, India. The experiment had nine treatments, each replicated three times in randomized blocks. The DI treatments labeled as T 1 to T 6 , were irrigated at CATD values of -4, -3, -2, -1, 0, and 1 °C, respectively.. While T 7 were irrigated by border irrigation. In order to define upper and lower baselines of CWSI, well watered treatments (T 8 ) and extreme dry treatment (T 9 ) DI were considered. The drip irrigation system (DIS) had an application rate of 7.78 mm/h with a uniformity coefficient of 90.40%. Compared to surface irrigation, DI resulted in water savings ranging from 3.52% (T 1 ) to 43.24% (T 6 ). Using real-time CATD data, the theoretical CWSI (CWSI Th ) and the vapor pressure deficit (VPD) based semi-empirical CWSI (CWSI VPD ) were calculated as 0.3351 and 0.3668, respectively. CATD values showed significant variation in CWSI across treatments. The CWSI demonstrated sensitivity to water stress during critical growth stages. The study identified an optimal CATD of -1 °C, yielding 36.48% higher crop yield (4744 kg/ha), 30.23% water savings (388.42 mm), and notable 95.67% more water use efficiency (12.21 kg/ha-mm,), surpassing the outcomes of border irrigation (3476 kg/ha, 556.74 mm and 6.24 kg/ha-mm). These findings hold significant implications for farmers and policymakers, effectively addressing food and water security concerns. The study underscores the efficiency of DI combined with CATD-based irrigation scheduling in optimizing wheat crop performance. In the context of critical water management, this research provides essential insights for sustainable agricultural practices.
... To overcome this problem, another approach proposed by Penman (1948), and later modified by Monteith (1973), avoids considering leaf temperature to deduce transpiration according to more easily accessible physical quantities: the radiation absorbed by the canopy and the air vapour pressure deficit (Katsoulas & Stanghellini, 2019). ...
... The reference crop evapotranspiration (E T0 ) is calculated using the Penman-Monteith equation, reliant on meteorological data from proximate weather stations in the experimental vicinity. Then, the PET of the crop is subsequently calculated using the single crop coefficient method, followed by using the Beer's law to separate the potential evaporation and potential transpiration components [35]. ...
This study aims to examine the impact of combined irrigation and fertilizer control on the summer maize yield, nitrogen use efficiency (NE), and nitrogen leaching (NL) in the Yellow River Basin. Based on the measured data from the field summer maize experiment in 2021 and 2022, a water-nitrogen movement model was constructed for ‘Zhengdan 958’ maize under two irrigation methods (wide furrow irrigation (G) and border irrigation (Q)), three fertilizer rates (120 kg/ha (N1), 220 kg/ha (N2), and 320 kg/ha (N3)), and three fertilizer frequencies (1 (T1), 2 (T2), and 3 (T3)), yielding 18 total treatments. Calculation of nitrogen leaching was based on water nitrogen transport modeling. The study then analyzed the factors and their combined effects. A multi-objective optimization genetic algorithm (NSGA-II) was established to evaluate maize yield, nitrogen use efficiency, and nitrogen leaching. The results indicate that the determination coefficients between simulated and measured water, nitrogen values exceeded 0.74. The rate optimized HYDRUS model effectively simulated the soil solute movement. The interaction of the irrigation method, fertilizer rate, and fertilizer application frequency did not significantly affect yield and nitrogen leaching, but did significantly impact nitrogen use efficiency (p < 0.05). Nitrogen leaching increased gradually as nitrogen application increased. The yield under wide furrow irrigation was 6.26% higher than that under border irrigation. The optimal coupling scheme of water and fertilizer was obtained using the genetic algorithm multi-objective optimization method, where the combined GN2T2 treatment was the optimal management model, the summer maize yield reached 14,077 kg/ha, nitrogen use efficiency and nitrogen leaching were reduced to 30.21 kg·kg−1 and 17.64 kg/ha, respectively. These findings can guide summer maize cultivation in the Yellow River Basin and assist in reducing nitrogen surface source pollution.
... (iv) Radiation use efficiency (RUE) for beans and maize can be calculated as (Monteith, [44] (Equations (11) and (12)): ...
The purpose of this study was to evaluate alternative management practices such as in-field rainwater harvesting (IRWH) and intercropping techniques through conducting on-farm demonstrations. Seven homestead gardens in Thaba Nchu rural communities in the central part of South Africa were selected as demonstration trials. Two tillage systems, conventional (CON) and IRWH, as the main plot, and three cropping systems as sub-plot (sole maize and beans and intercropping) were used to measure water use and radiation use parameters. The water productivity (WP) of various treatments was positively related to the radiation use efficiency (RUE), and the degree of associations varied for different tillage systems. The water use in IRWH was higher by 15.1%, 8.3%, and 10.1% over the CON for sole maize and beans and intercropping, respectively. Similarly, the intercropping system showed water use advantages over the solely growing crops by 5% and 8% for maize and by 16% and 12% for beans under IRWH and CON tillage, respectively. Maximum RUE was found for sole maize and beans under IRWH, higher by 13% and 55% compared to the CON tillage, respectively. The RUE under IRWH tillage was estimated to be 0.65 and 0.39 g DM MJ−1 in sole maize and intercropping, respectively. However, in sole and intercropped beans, the RUE showed higher values of 1.02 g DM MJ−1 and 0.73 g DM MJ−1, respectively. WP and RUE were associated with water deficits and proportional to lower radiation use. This relationship indicates that the intercepted radiation by plants for photosynthesis is directly related to the transpiration rate until radiation saturation occurs. Therefore, the higher water deficit and lesser efficiency in using the radiation available during the season can be improved by practicing IRWH techniques. Furthermore, in semi-arid areas, to enhance the efficiency of water and radiation usage in intercropping management, it is crucial to adjust plant population and sowing dates based on water availability and the onset of rainfall.
... To overcome this problem, another approach proposed by Penman (1948), and later modified by Monteith (1973), avoids considering leaf temperature to deduce transpiration according to more easily accessible physical quantities: the radiation absorbed by the canopy and the air vapour pressure deficit (Katsoulas & Stanghellini, 2019). ...
... The VIC model additionally includes mosaic land cover to capture sub-grid variability in vegetation classes, an important element in this study with which to aid representation of sub-grid variability in vegetation mortality. Within VIC, ET was dynamically computed from Penman-Monteith PET (Monteith, 1973), modified by stomatal and architectural vegetation resistance terms, and coupled to annual MODIS-derived vegetation parameters (Bohn and Vivoni, 2019) to evaluate changes in water and energy balances. Updated daily precipitation, maximum and minimum air temperature, and wind forcings were used in conjunction with an offline J.F. Knowles et al. ...
Insect outbreaks affect forest structure and function and represent a major category of forest disturbance globally. However, the resulting impacts on evapotranspiration (ET), and especially hydrological partitioning between the abiotic (evaporation) and biotic (transpiration) components of total ET, are not well constrained. As a result, we combined remote sensing, eddy covariance, and hydrological modeling approaches to determine the effects of bark beetle outbreak on ET and its partitioning at multiple scales throughout the Southern Rocky Mountain Ecoregion (SRME), USA. At the eddy covariance measurement scale, 85 % of the forest was affected by beetles, and water year ET as a fraction of precipitation (P) decreased by 30 % relative to a control site, with 31 % greater reductions in growing season transpiration relative to total ET. At the ecoregion scale, satellite remote sensing masked to areas of >80 % tree mortality showed corresponding ET/P reductions of 9-15 % that occurred 6-8 years post-disturbance, and indicated that the majority of the total reduction occurred during the growing season; the Variable Infiltration Capacity hydrological model showed an associated 9-18 % increase in the ecoregion runoff ratio. Long-term (16-18 year) ET and vegetation mortality datasets extend the length of previously published analyses and allowed for clear characterization of the forest recovery period. During that time, transpiration recovery outpaced total ET recovery, which was lagged in part due to persistently reduced winter sublimation, and there was associated evidence of increasing late summer vegetation moisture stress. Overall, comparison of three independent methods and two partitioning approaches demonstrated a net negative impact of bark beetles on ET, and a relatively greater negative impact on transpiration, following bark beetle outbreak in the SRME.
... The daily weather data, including precipitation, temperature, dewpoint, wind, and solar radiation, was generated by a Stochastic Weather Generator named Cligen (Meyer et al., 2008), using site climate parameters derived from the historical measurement of Nanning station, China, during 1990-2019 (available on http://data.cma.cn/). As one of the crucial input variables of AquaCrop, ETo was calculated by the Penman-Monteith model using the generated weather data (Monteith, 1973;Allen et al., 1998). ...
... While many SA computations have been published, most are inaccurate, impractical, or may not be readily available when a determination must be made. Regardless, the surface area is a reasonable method of estimation for body mass given that heat (or cold) and, thus, energy exchange processes between an animal and the environment occur through the animal's surface [68]. This is important given that, similar to very low temperatures, livestock performance at higher temperatures (e.g., sub-tropical, tropical) can result in poorer weight gain performance [67,69,70]. ...
Estimates of global population growth are often cited as a significant challenge for global food production. It is estimated that by 2050 there will be approximately two-billion additional people on earth, with the greatest proportion of that growth occurring in central Africa. To meet recommended future protein needs (60 g/d), approximately 120 million kg of protein must be produced daily. The production of ruminant meat (particularly beef cattle) offers the potential to aid in reaching increased global protein needs. However, advancements in beef cattle production are necessary to secure the industry's future sustainability. This article draws attention to a subset of sustainable beef cattle production challenges, including the role of ruminant livestock in meeting global human protein needs, the environmental relationships of advanced beef cattle production, and big data and machine learning in beef cattle production. Considering the significant quantities of resources necessary to produce this form of protein, such advancements are not just a moral imperative but critical to developing advanced beef cattle production practices and predictive models that will reduce costs and liabilities and advance industry sustainability.
... This is expected as the measurements were carried out in the middle of the canopy where a great part of L in is from the surrounding leaves at a similar temperature. While the absorption of longwave radiation is difficult to modify, leaves can reduce the amount of absorbed shortwave radiation through adaptations of their pigmentation, shape and/or orientation (Leigh et al. 2017;Smith and Carter 1988;Monteith 1973;Landsberg and Thom 1971;Michaletz and Johnson 2006;Gates 1962). Note also that the magnitude of L emitted was nearly identical between treatments because leaf temperature and emissivity were similar too at our study site (Muller et al. 2021a). ...
The modulation of the leaf energy budget components to maintain optimal leaf temperature are fundamental aspects of plant functioning and survival. Better understanding these aspects becomes increasingly important under a drying and warming climate when cooling through evapotranspiration (E) is suppressed. Combining novel measurements and theoretical estimates, we obtained unusually comprehensive twig-scale leaf energy budgets under extreme field conditions in droughted (suppressed E) and non-droughted (enhanced E) plots of a semi-arid pine forest. Under the same high mid-summer radiative load, leaf cooling shifted from relying on nearly equal contributions of sensible (H) and latent (LE) energy fluxes in non-droughted trees to relying almost exclusively on H in droughted ones, with no change in leaf temperature. Relying on our detailed leaf energy budget, we could demonstrate that this is due to a 2× reduction in leaf aerodynamic resistance. This capability for LE-to-H shift in leaves of mature Aleppo pine trees under droughted field conditions without increasing leaf temperature is likely a critical factor in the resilience and relatively high productivity of this important Mediterranean tree species under drying conditions. This article is protected by copyright. All rights reserved.
... In the FAO-56 single crop coe cient approach, the effect of both crop transpiration and soil evaporation are integrated into a single crop coe cient (Kc). However, crop evapotranspiration (ETc) estimation is more accurate by dual crop coe cient approach than the single crop coe cient approach, the dual crop coe cient approach uses more parameters and take soil practices and crop characteristics into consideration (Monteith, 1973, Ventura et al., 1999, Zhang et al., 2013). In the dual approach a daily basal crop coe cient (Kcb), representing primarily the plant transpiration, and a daily soil evaporation coe cient (Ke) are considered separately according to the equation: ...
A field trial was conducted to investigate the effects of regulated dry season irrigation on tree water use, root zone moisture dynamics and yield of cacao in a rainforest zone of Nigeria. Following cessation of rainfall in November, irrigation commenced from December 2017 to May 2018. Irrigation amount was computed based on cumulative class A Pan evaporation. Irrigation treatments were coded as IrT1, IrT2 and IrT3, consisting of water application using EPan *Pan coefficients (Kcp) of 1.0; 0.70 and 0.50 (9.6, 6.8 and 4.8 l/tree/day). Irrigation water applied at 5-days interval was discharged via point source emitters (2.8 l/h discharge rate ) on drip lines laterally installed per row of trees. Irrigation requirements were on the average, 4.49, 3.14 and 2.44 mm, total water applied per irrigation events were 1009.88, 706.92 and 504.94 mm per plot ( 225 m ² ), total seasonal water applied were 33858, 23701 and 16929 mm, and soil moisture contents were 52, 45 and 28% for the respective IrT1, IrT2 and IrT3. Tree evapotranspiration (ETc) were 4.54, 3.19 and 2.32 mm/day while seasonal sums were 809, 566 and 404 mm while the ratio of ETc to EPan were 0.9, 0.69 and 0.53 for IrT1, IrT2 and IrT3. Tree water use efficiencies were 0.3 and 0.04 t/mm for Y/ETc and 0.16 to 0.19 kg/mm for Y/Irrigation respectively. Cacao pod and bean yields were 35.4, 22.1 and 10.3 t/ha and 2.29, 1.37 and 1.03 t/ha while yields decreased by 60 and 40% under IrT3 and IrT2 compared with IrT1. The study identified suitable Pan coefficients for scheduling irrigation during the dry season for cacao, full irrigation (EPan*1.0) applied at 9.6 l/tree/day will be needed to replenish soil water depletion to satisfy crop consumptive water use ( transpiration and soil evaporation components). The low pressure gravity-drip irrigation system alleviated climate stress during the dry season and improved cacao performance in a tropical rainforest environment.
... where the ratio of soil heat flux to net radiation Γ c = 0.315 for a full-vegetation canopy [37] and Γ s = 0.05 for bare soil [38]. An interpolation was conducted between these limiting cases by applying the fractional canopy coverage, f c . ...
Water-use efficiency (WUE) is a crucial physiological index in carbon–water interactions and is defined as the ratio of vegetation productivity to water loss. The variation in climatic variables and drought have the most significant effects on WUE and evapotranspiration (ET). Nevertheless, how WUE varies with climate factors and drought processes in the Tianshan Mountains (TMS) is still poorly understood. In the present work, we analyzed the spatiotemporal variations in WUE, and investigated the correlations between WUE, climate factors, and drought, in the study area. The results showed that, in the TMS during 2000–2020, annual net primary productivity (NPP) ranged from 147.9 to 189.4 gC·m−2, annual ET was in the range of 212.5–285.8 mm, and annual WUE ranged from 0.66 to 0.78 gC·kg−1·H2O. Both NPP and ET exhibited an increasing trend with some fluctuation, whereas WUE showed the opposite tendency during the study period. The obtained results demonstrated that the decrease in WUE was primarily because of the increase in ET. There were obvious differences in WUE, under different land-use types, caused by NPP and ET. However, the interannual variation in WUE showed small fluctuations and the dynamic process of WUE in each land-use type showed good consistency. Temperature and wind speed had a positive influence on WUE in the middle and eastern regions of the TMS. Precipitation also played a mainly positive role in enhancing WUE, especially on the northern slope of the TMS. There was strong spatial heterogeneity of the correlation coefficient (0.68, p < 0.05) between WUE and the temperature vegetation drought index (TVDI). Moreover, the slopes of WUE and TVDI showed good consistency in terms of spatial distribution, suggesting that drought had a significant impact on ecosystem WUE. This work will enhance the understanding of WUE variation, and provide scientific evidence for water resource management and sustainable utilization in the study area.
... Corn planting density also affects yield and quality. It is generally believed that low planting densities lead to a decrease in dry matter accumulation per unit area, which in turn reduces maize yield and agronomic traits [22][23][24][25]. On the contrary, high planting density will lead to an increase in the canopy area of maize colonies, and poor colony ventilation conditions will lead to intense competition for light resources, which will cause maize stem nodes to be thin and prone to lodging [26]. ...
Planting density and N fertilizer application amount directly affect the planting quality of maize. Therefore, this study analyzed the impact of these two factors on light energy utilization and yield. The field experiment was carried out with Xinyu 57 maize as the experimental variety. An experiment was set up with four different planting densities and three different N fertilizer concentrations. The light use efficiency, productivity, and growth of maize were observed. The effects of planting density and N fertilization on light use efficiency at the heading stage were analyzed in detail. Finally, it was concluded that high-density planting and the proper application of N fertilizer can significantly improve the light energy efficiency and yield of maize. High-density planting has a significant effect on corn light energy utilization. Increasing N fertilizer can improve the photosynthetic characteristics of plants, increase the content of photosynthetic pigments in maize ear leaves, and improve the utilization rate of light energy and yield.
... where k is the Von Kármán constant, taken as 0.41. n is the extinction coefficient of eddy diffusion, with a typical value of 2.5 usually chosen for crops (wheat (Triticum aestivum L.), rice (Oryza sativa L.), clover (Trifolium repens L.), and maize) (Monteith, 1973). n can also be determined by linear interpolation as follows (Brutsaert, 1982): ...
The joint application of plastic mulch and interplanted patterns significantly increases the utilization efficiencies of water and energy in arid regions. Each individual crop transpiration directly related with agricultural production. Soil evaporation under transparent plastic mulch is decreased but can not be ignored especially under the condition with higher soil moisture and large film mulching fraction (fm). Accurate estimation of evapotranspiration (λET) and its components (transpiration, λTrc and its sub-components (individual plant transpiration, λTrci); soil evaporation, λEs and its sub-components (bare soil evaporation, λEsbs; and mulched soil evaporation, λEsms)) for partial mulched interplanted croplands is essential for water resources management. In this study, a multiple source evapotranspiration model (SWIM) was proposed to accurately estimate λET and its components in partially mulched interplanted croplands based on Shuttleworth-Wallace model (SW). In SWIM, the effect of partial plastic mulch was accounted for by introducing fm and mulched soil resistance (rsm), while the effect of intercepted energy distribution between the intercropped plants was considered by integrating a light-interception sub-model. The performance of the SWIM model was evaluated against measurements from two partially mulched intercropped seed maize field under border irrigation (BM) and drip irrigation (DM) during different growth periods. The results showed that: (1) the SWIM model accurately estimated λET and its components and outperformed the SW model during the entire growing season, especially significantly improved these items estimations during the sparse canopy growth period, with reduced NRMSE of 0.18 and 0.33, 0.25 and 0.20, 0.26 and 0.49 for λET, λTrc, and λEs of BM and DM sites, respectively; (2) better performance of the SWIM model in λTrci estimation during the dense canopy growth period and in λEsbs and λEsms estimation during the sparse period was demonstrated, with reduced NRMSE of 0.09–0.11 and 0.11–0.12, 0.04 and 0.02, 0.02 and 0.05 for λTrci, λEsbs, and λEsms of BM and DM sites, respectively. This study will improve our understanding of eco-hydrology processes in the soil-mulch-plant-atmosphere continuum and provide a scientific basis for water resource management in arid regions.
... The sensible heat flux is calculated using the Monin-Obukhov similarity theory (Kondo & Ishida, 1997). The soil heat flux (G) is assumed to be proportional to the net radiation using ratios of ground heat flux to net radiation (Monteith, 1973; W. P. Kustas & Daughtry, 1990). G is scaled by vegetation cover (Choudhury et al., 1994). ...
Evapotranspiration (ET) provides a robust connection between hydrological cycles and surface energy balance. Accurate and near‐daily ET estimation has utility in water resources, agricultural management applications, crop yields and drought monitoring. This study describes the implementation of an ET modeling system based on a Priestley‐Taylor version of the Two‐Source (soil and vegetation) Energy Balance Model (TSEB‐PT) within Google Earth Engine environment. TSEB‐PT performance was compared with the simpler single‐source HSEB (Hybrid Surface Energy Balance) ET model to assess relative advantages and disadvantages for operational application. Results were evaluated across multiple biomes and climatic zones across the US, Europe, and Australia in comparison with eddy covariance data from 30 flux tower sites. Both models produced similar results when considering all biomes at daily, weekly, and monthly timescales. Daily ET metrics for all sites combined yielded comparable results for both models, with a slightly lower root‐mean‐square error for TSEB‐PT (HSEB) of 1.2 (1.3) mm/d and a higher correlation (r) of 0.83 (0.80), but a larger mean percent bias error (MPBE = −9%) than HSEB (MPBE = 1%). TSEB‐PT performance was lowest for sites in warm summer humid continental and hot semi‐arid climates and in evergreen broadleaf forest cover, while HSEB showed lowest performance in tropical savanna hot semi‐arid climates and in savanna covers. Model performance was improved for both cropland and non‐cropland sites when TSEB‐PT and HSEB ET estimates were combined through simple averaging due to cancellation of opposing errors, showing a promise as potential tools for water resource management on a global scale.
Simulations of the processes contributing to the deposition of trace gases and small particles from the air to natural surfaces routinely describe the consequences of changing molecular diffusivity in terms of the Schmidt number, Sc ≡ ν/D, where ν is kinematic viscosity and D the molecular diffusivity of the constituent in question. Using well-verified results of pipe flow experiments, early workers proposed that the relevant property entering dry deposition and other models of similar kind should be Sc−2/3 rather than Sc⁻¹ as would be expected from historic flat plate experiments. Upon reconsideration, it is now proposed that no universal power-law dependence on Sc can be expected; the corresponding role of molecular diffusivity is likely to be site-specific. Relevant experimental evidence remains elusive.
The shortage of decades‐long continuous measurements of ecosystem processes limits our understanding of how changing climate impacts forest ecosystems. We used continuous eddy‐covariance and hydrometeorological data over 2002–2022 from a young Douglas‐fir stand on Vancouver Island, Canada to assess the long‐term trend and interannual variability in evapotranspiration ( ET ) and transpiration ( T ). Collectively, annual T displayed a decreasing trend over the 21 years with a rate of 1% yr ⁻¹ , which is attributed to the stomatal downregulation induced by rising atmospheric CO 2 concentration. Similarly, annual ET also showed a decreasing trend since evaporation stayed relatively constant. Variability in detrended annual ET was mostly controlled by the average soil water storage during the growing season (May–October). Though the duration and intensity of the drought did not increase, the drought‐induced decreases in T and ET showed an increasing trend. This pattern may reflect the changes in forest structure, related to the decline in the deciduous understory cover during the stand development. These results suggest that the water‐saving effect of stomatal regulation and water‐related factors mostly determined the trend and variability in ET , respectively. This may also imply an increase in the limitation of water availability on ET in young forests, associated with the structural and compositional changes related to forest growth.
Canopy conductance is a crucial factor in modelling plant transpiration and is highly responsive to water stress. The objective of this study is to develop a straightforward method for estimating canopy conductance (gc) in grapevines. To predict gc, this study combines stomatal conductance to water vapor (gsw) measurements from grapevine leaves, scaled to represent the canopy size by the leaf area index (LAI), with atmospheric variables, such as net solar radiation (Rn) and air vapor pressure deficit (VPD). The developed model was then validated by comparing its predictions with gc values calculated using the inverse of the Penman Monteith equation. The proposed model demonstrates its effectiveness in estimating the gc, with the highest root-mean-squared-error (RMSE=1.45x10⁻⁴ m.s⁻¹ ) being lower than the minimum gc measured in the field (gc obs=0.0005 m.s⁻¹ ). The results of this study reveal the significant influence of both VPD and gsw on grapevine canopy conductance.
Railway mountain tunnels were constructed in cold regions of Korea recently, and freezing has been generated. Most mountainous railway tunnels are designed with waterproofing membranes since groundwater exists on the backside of the tunnels. The lower air temperature inside the tunnel is transferred to the back of the tunnel lining as the outside air temperature drops below zero in winter, causing the groundwater behind the waterproofing membrane to freeze. There have been cases of freezing-related damage, such as the obstruction of drainage flow and freezing groundwater leakage. Therefore, the freezing conditions inside the tunnel should be analyzed by each tunnel length after the air temperature variation in the tunnel is measured. In this study, the air temperature inside a railway tunnel located in a cold region was measured using thermometers. The inside air temperature over time was changed by the DTR (diurnal temperature range) every 24 h. The DTR inside the tunnel was also reduced far from the entrance. Heat transfer analysis was implemented considering the air temperature variation inside the tunnel. Assuming that the minimum air temperature freezing inside the tunnel lasts seven days, the higher the minimum air temperature the longer the tunnel length. The research results show that the freezing inside a tunnel can be estimated from the tunnel length and the minimum air temperature inside the tunnel.
In this paper, the modelling and thermal performance results of the solar air collector have been presented. This system is conceived to heat the ambient air in order to be used in many domains like drying processes and heating buildings. The pseudo-bond graph methodology was used in modelling this system. Such methodology was very suitable for this thermodynamic process since it allows good management of the non-linearity present in the system. The simulation of the global model with bond graph software [20-sim] allows us to analyze the temperature variations and the efficiency of the solar collector and compared with experiment results.
The decoupling factor (Ω) reflects the leading mechanisms responsible for canopy transpiration and allows to know the relevance of the control of stomatal or canopy conductance on transpiration (T). The Ω is strongly dependent on water availability and can be a good approach to describe how plants minimize excessive water loss by increasing the dominance of biotic factors that controls evapotranspiration under water deficit conditions. We provided an overview of how the Ω concept can be broadly used and applied for studying the sensitivity of evapotranspiration and water conservation potential of canopies under water deficit conditions. A decoupling condition indicates that, under water deficit, the increase of canopy resistance will not have control over the transpiration. Therefore, a structural context of the canopy in which predominantly uncoupled regions will have a lower capacity to reduce evapotranspiration and avoid water losses. Furthermore, because of the water deficit, stomatal closure restricts photosynthesis more than transpiration, and water use efficiency can be lower in decoupled canopies compared to more coupled ones. Yet, we summarized the characteristics that depict structural context predisposing coupled or decoupled conditions that can indicate the capacity of canopy/crop to reduce excessive water losses and maintain a high assimilation/transpiration relation under water deficit.e farmers to design disease management programs accordingly to avert yield losses.
Key words
transpiration; water deficit; vapor pressure deficit; decoupling factor
Plant breeding for increased crop water use efficiency or drought stress resistance requires methods to quickly assess the transpiration rate (E) and stomatal conductance (gs) of a large number of individual plants. Several methods to measure E and gs exist, each of which has its own advantages and shortcomings. To add to this toolbox, we developed a method that uses whole-plant thermal imaging in a controlled environment, where aerial humidity is changed rapidly to induce changes in E that are reflected in changes in leaf temperature. This approach is based on a simplified energy balance equation, without the need for a reference material or complicated calculations. To test this concept, we built a double-sided, perforated, open-top plexiglass chamber that was supplied with air at a high flow rate (35Lmin-1) and whose relative humidity (RH) could be switched rapidly. Measurements included air and leaf temperature as well as RH. Using several well-watered and drought stressed genotypes of Arabidopsis thaliana that were exposed to multiple cycles in RH (30 to 50% and back), we showed that leaf temperature as measured in our system correlated well with E and gs measured in a commercial gas exchange system. Our results demonstrate that, at least within a given species, the differences in leaf temperature under several RH can be used as a proxy for E and gs. Given that this method is fairly quick, noninvasive and remote, we envision that it could be upscaled for work within rapid plant phenotyping systems.
Associated with climate change, the frequency, duration, and intensity of heatwaves are increasing in most of the key wine regions worldwide. Depending on timing, intensity, and duration, heatwaves can impact grapevine yield and berry composition, with implications for wine quality. To overcome these negative effects, two types of mitigation practices have been proposed (i) to enhance transpiration and (ii) to reduce the radiation load on the canopy. Here we use a biophysical model to quantify the impact of these practices on canopy gas exchange, vine water status, and leaf temperature (T l). Model validation was performed in a commercial vineyard. Modelled T l from 14 to 43 • C, and transpiration, from 0.1 to 5.4 mm d − 1 , aligned around the identity line with measurements in field-grown vines; the RMSD was 2.6 ºC for temperature and 0.96 mm day − 1 for transpiration. Trellis system and row orientation modulate T l. A sprawling single wire trellis with an EW orientation maintained the canopy around 1ºC cooler than a Vertical Shoot Positioned canopy with NS for the same range of total fraction of soil available water (TFAW). Although irrigation before a heatwave is a recommended practice, maximum transpi-ration can be sustained even when TFAW is reduced, limiting the heat dampening effect of irrigation. Alternatively , canopy cooling can be achieved through Kaolin application, the installation of shade cloth placement, or canopy trimming. Shade cloth produced a greater cooling than Kaolin in all the simulated scenarios; however, T l differences between them varied. Trimming reduced T l from 2 ºC to almost 8 ºC compared to its non-trimmed counterpart. Our analysis presents new insights to design heat wave mitigation strategies and supports agro-nomically meaningful definitions of heat waves that include not only temperature, but also wind, VPD, and radiation load as these factors influence crop physiology under heat stress.
Biogeoscience is a rapidly growing interdisciplinary field that aims to bring together biological and geophysical processes. This book builds an enhanced understanding of ecosystems by focusing on the integrative connections between ecological processes and the geosphere, hydrosphere and atmosphere. Each chapter provides studies by researchers who have contributed to the biogeoscience synthesis, presenting the latest research on the relationships between ecological processes, such as conservation laws and heat and transport processes, and geophysical processes, such as hillslope, fluvial and aeolian geomorphology, and hydrology. Highlighting the value of biogeoscience as an approach to understand ecosystems, this is an ideal resource for researchers and students in both ecology and the physical sciences.
Canopy conductance (gc) is an important biophysical parameter closely related to ecosystem energy partitioning and carbon sequestration, which can be used to judge drought effect on forest ecosystems. It is very important to explore how soil moisture change affects the environmental control mechanism of gc, especially in natural oak forests in Central China where frequent extreme precipitation (P) and drought will occur in a context of climate change. In this study, variations of gc and its environmental control mechanisms in a warm-temperate forest over three consecutive years under different hydroclimatic conditions were examined by using eddy-covariance technique. Results showed that the averaged gc in the three growing seasons were 11.2, 11.3 and 7.8 mms-1, respectively, with a CV of 19.7 %. The lowest gc occurred in the year with the lowest P. Using three years of data, we found that vapor pressure deficit (VPD) exhibited the dominate effect on gc, both diffuse photosynthetically active radiation (PARdif) and air temperature (Ta) were positively correlated with gc. When relative extractable water content (REW) was larger than 0.4, however, inhibiting effect of high VPD on gc disappeared and the effect of direct photosynthetically active radiation (PARdir) on gc was larger compared to PARdif. When REW was <0.1, the positive relationship between Ta and gc became negative. Our results indicated that soil moisture ultimately shapes the environmental control mechanism of gc in a natural oak forest.
Growth chambers can be adapted in many ways to meet the special needs of plant stress studies. The purpose of this paper is to discuss special growth chambers and selected stress experiments requiring special techniques and extensive modification of growth chamber design. Use of growth chambers in air pollution, pesticide, radioisotope, and ultraviolet radiation research will be presented as examples.
Thermal physiology research is entirely dependent on the ability to measure temperature, and that could not happen until the invention of the thermometer by Santorio Santorio in 1612. However, it was not until 1724 that Daniel Gabriel Fahrenheit devised an accurate scale of temperature measurement, followed by the Swedish scientist, Anderss Celsius in 1742, who invented the centigrade (Celsius) scale. It was much later, in 1867, that Sir Thomas Allbutt invented the first practical medical thermometer, and soon after James Joule (1850) demonstrated the relationship between thermal energy and mechanical work. However, with some exceptions (e.g. Blagden, 1775), scientific observations on the physiology of temperature regulation did not really begin in the UK until the end of the eighteenth century. Anyone entering the field of human thermal physiology could adopt the principle of not exposing others experimentally to conditions to which they have not exposed themselves. In preparation, read the well-known heroic tale of how the UK physician and scientist Charles Blagden (Fig. 1.1) exposed himself and other volunteers (including a dog) to air temperatures up to 127 °C, much hotter than modern saunas (see Chap. 4) and enough to cook a steak alongside him, as he demonstrated, and found, to his relief, that sweating kept the deep-body temperatures in the low forties.
Accurately quantifying the impacts of climate change on global hydrological cycles is essential for water resource management. Integrated with the Global Land Surface Satellite (GLASS) leaf area index (LAI), the actual evapotranspiration (ETa) from 1981 to 2012 in eight major river basins (Amazon, Mississippi, Yangtze, Mekong, Lena, Murray-Darling, Nile, and Rhine) was simulated with the VIP (Vegetation Interface Processes) ecohydrological dynamic model. The sensitivities and contributions of ETa to climatic change and vegetation greening were explored with the elasticity coefficient method. The results showed that the simulated monthly ETa was consistent with the eddy covariance measurements (determination coefficient (R²) ranged from 0.5 to 0.85, p < 0.01). The simulated annual ETa was also in good agreement with those from the annual water balance (R² = 0.89, p < 0.01) across the eight basins. The relative annual ETa trends in the Amazon and Mississippi basins were negative, approximately -0.09% year⁻¹, whereas the annual increasing trends in other basins ranged from 0.16% year⁻¹ to 0.39% year⁻¹. In the Yangtze and Mekong basins, ETa was more sensitive to vegetation greening, however climatic changes were the primary drivers of ETa tendencies in the other six basins in which the dominant driving factors were different, shifted from precipitation in the Mississippi, Murray-Darling and Nile basins to solar radiation in the Amazon basin. Specifically, precipitation and air temperature equivalently contributed to the ETa trend in the Lena Basin. The variations in ETa were strongly linked with El Niño events in the Amazon basin (energy-limited region) and Murray-Darling basin (water-limited region), reflecting the impacts of global climate extremes.
A model that computes orchard foliage temperature distributions in a heated orchard is described. The energy balance for individual foliage elements is computed, considering thermal radiation from the environment, plus the radiative and convective effects of an array of orchard heaters. The model is used to analyze various heater configurations and densities, and to determine rates of fuel consumption required for frost protection. The results indicate that radiative heating of the foliage by the heaters is as important as convective heating of the air, even though only one-fifth of the fuel contributes to radiation emission. Further, results suggest several simple passive methods for increasing the efficiency of orchard heating.
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