Daily grass reference evapotranspiration with Meteosat Second Generation shortwave radiation and reference ET products

Second Step ◽

Urban Water ◽

Biological Engineering ◽

Fact Sheet ◽

Water Users ◽

Irrigation Requirements ◽

Urban water users need specific recommendations to irrigate efficiently and for planning and regulatory programs. As the second step in the process of estimating net irrigation requirements. This 9-page fact sheet calculates reference ET for ten locations in Florida and one in Alabama. Written by Consuelo C. Romero and Michael D. Dukes and published by the UF Department of Agricultural and Biological Engineering, August 2011. (Image from ca.gov) http://edis.ifas.ufl.edu/ae481

Divergence of actual and reference evapotranspiration observations for irrigated sugarcane with windy tropical conditions

Hydrology and Earth System Sciences ◽

10.5194/hess-19-583-2015 ◽

2015 ◽

Vol 19 (1) ◽

pp. 583-599 ◽

Cited By ~ 8

Author(s):

R. G. Anderson ◽

D. Wang ◽

R. Tirado-Corbalá ◽

H. Zhang ◽

J. E. Ayars

Keyword(s):

Canopy Cover ◽

Stomatal Resistance ◽

Canopy Resistance ◽

Tropical Regions ◽

Tropical Environments ◽

Tropical Conditions ◽

The Difference ◽

American Society ◽

Abstract. Standardized reference evapotranspiration (ET) and ecosystem-specific vegetation coefficients are frequently used to estimate actual ET. However, equations for calculating reference ET have not been well validated in tropical environments. We measured ET (ETEC) using eddy covariance (EC) towers at two irrigated sugarcane fields on the leeward (dry) side of Maui, Hawaii, USA in contrasting climates. We calculated reference ET at the fields using the short (ET0) and tall (ETr) vegetation versions of the American Society for Civil Engineers (ASCE) equation. The ASCE equations were compared to the Priestley–Taylor ET (ETPT) and ETEC. Reference ET from the ASCE approaches exceeded ETEC during the mid-period (when vegetation coefficients suggest ETEC should exceed reference ET). At the windier tower site, cumulative ETr exceeded ETEC by 854 mm over the course of the mid-period (267 days). At the less windy site, mid-period ETr still exceeded ETEC, but the difference was smaller (443 mm). At both sites, ETPT approximated mid-period ETEC more closely than the ASCE equations ((ETPT-ETEC) < 170 mm). Analysis of applied water and precipitation, soil moisture, leaf stomatal resistance, and canopy cover suggest that the lower observed ETEC was not the result of water stress or reduced vegetation cover. Use of a custom-calibrated bulk canopy resistance improved the reference ET estimate and reduced seasonal ET discrepancy relative to ETPT and ETEC in the less windy field and had mixed performance in the windier field. These divergences suggest that modifications to reference ET equations may be warranted in some tropical regions.

Divergence of reference evapotranspiration observations with windy tropical conditions

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-6473-2014 ◽

2014 ◽

Vol 11 (6) ◽

pp. 6473-6518 ◽

Cited By ~ 2

Author(s):

R. G. Anderson ◽

D. Wang ◽

R. Tirado-Corbalá ◽

H. Zhang ◽

J. E. Ayars

Keyword(s):

Canopy Cover ◽

Stomatal Resistance ◽

Canopy Resistance ◽

Tropical Regions ◽

Tropical Environments ◽

Tropical Conditions ◽

The Difference ◽

American Society ◽

Abstract. Standardized reference evapotranspiration (ET) and ecosystem-specific vegetation coefficients are frequently used to estimate actual ET. However, equations for calculating reference ET have not been well validated in tropical environments. We measured ET (ETEC) using Eddy Covariance (EC) towers at two irrigated sugarcane fields on the leeward (dry) side of Maui, Hawaii, USA in contrasting climates. We calculated reference ET at the fields using the short (ET0) and tall (ETr) vegetation versions of the American Society for Civil Engineers (ASCE) equation. The ASCE equations were compared to the Priestley–Taylor ET (ETPT) and ETEC. Reference ET from the ASCE approaches exceeded ETEC during the mid-period (when vegetation coefficients suggest ETEC should exceed reference ET). At the windier tower site, cumulative ETr exceeded ETEC by 854 mm over the course of the mid-period (267 days). At the less windy site, mid-period ETr still exceeded ETEC, but the difference was smaller (443 mm). At both sites, ETPT approximated mid-period ETEC more closely than the ASCE equations ((ETPT–ETEC) < 170 mm). Analysis of applied water and precipitation, soil moisture, leaf stomatal resistance, and canopy cover suggest that the lower observed ETEC was not the result of water stress or reduced vegetation cover. Use of a custom calibrated bulk canopy resistance improved the reference ET estimate and reduced seasonal ET discrepancy relative to ETPT and ETEC for the less windy field and had mixed performance at the windier field. These divergences suggest that modifications to reference ET equations may be warranted in some tropical regions.

Implementing Standardized Reference Evapotranspiration and Dual Crop Coefficient Approach in the DSSAT Cropping System Model

Transactions of the ASABE ◽

10.13031/trans.12321 ◽

2017 ◽

Vol 60 (6) ◽

pp. 1965-1981 ◽

Cited By ~ 12

Author(s):

Kendall C. DeJonge ◽

Kelly R. Thorp

Keyword(s):

Cropping System ◽

Crop Coefficient ◽

Current Approach ◽

System Model ◽

Published Data ◽

Area Index ◽

Evaporation Coefficient ◽

Crop Coefficients ◽

Abstract. While methods for estimating reference evapotranspiration (ETo or ETr) and subsequent crop ET (ETc) via crop coefficient (Kc) and dual crop coefficient (Kcb, Ke) methods have been standardized since 2005 and 1998, respectively, the current version of the DSSAT cropping system model (CSM) has not been updated to fully implement these methods. In this study, two major enhancements to the model’s ET routines were evaluated: (1) addition of the ASCE Standardized Reference Evapotranspiration Equation so that both grass and alfalfa reference ET were properly calculated using the most recent reference ET standard and (2) addition of the FAO-56 dual crop coefficient approach to determine potential ET, which combined an evaporative coefficient (Ke) for potential evaporation with a dynamic basal crop coefficient (Kcb) for potential transpiration as a function of simulated leaf area index. Previously published data sets for maize in Colorado (five years) and cotton in Arizona (seven years) were used to parameterize the model. Simulations of ETo were compared to outputs from Ref-ET software, and simulated crop coefficients were contrasted among three crop coefficient methods: the current approach (Kcs), a previously published adjustment to the model’s Kc equation (Kcd), and a new dual Kc approach that follows FAO-56 explicitly (Kcb). Results showed that crop coefficient simulations with the new ETo-Kcb method better mimicked theoretical behavior, including spikes in the soil evaporation coefficient (Ke) due to irrigation and rainfall events and basal crop coefficient response as associated with simulated crop growth. Simulated ETc and yield with the new ETo-Kcb method were up to 4% higher and 28% lower for cotton and up to 13% higher and 26% lower for maize, respectively, than that with the current ETo-Kcs method, indicating that the seasonal ETc effects were minimal while yield effects were more substantial. Use of FAO-56 concepts and current ET standards in DSSAT-CSM demonstrated a well-accepted ET benchmark to guide assessment of other ET methods in the model and made the model much more conceptually relevant to irrigation and ET specialists. Keywords: Cotton, DSSAT, Evaporation, Evapotranspiration, FAO-56, Maize, Reference crop ET, Standardization, Transpiration.

Validation of reference evapotranspiration from Meteosat Second Generation (MSG) observations

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2018.05.008 ◽

2018 ◽

Vol 259 ◽

pp. 271-285 ◽

Cited By ~ 17

Author(s):

Isabel F. Trigo ◽

Henk de Bruin ◽

Frank Beyrich ◽

Fred C. Bosveld ◽

Pedro Gavilán ◽

...

Keyword(s):

Second Generation ◽

Reference Evapotranspiration

A Novel Approach for the Simulation of Reference Evapotranspiration and Its Partitioning

Agriculture ◽

10.3390/agriculture11050385 ◽

2021 ◽

Vol 11 (5) ◽

pp. 385

Author(s):

Pei Wang ◽

Jingjing Ma ◽

Juanjuan Ma ◽

Haitao Sun ◽

Qi Chen

Keyword(s):

Ecosystem Model ◽

Utilization Efficiency ◽

Shortwave Radiation ◽

Agricultural Ecosystem ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Novel Approach ◽

Crop Type ◽

Input Variables

To estimate the irrigation volume required for agriculture and improve water resources utilization efficiency, it is essential to obtain an estimate of reference evapotranspiration (ET0) and its components (e.g., reference transpiration, T0 and reference soil evaporation, E0). This study updated a soil-plant-atmosphere continuum (SPAC) evapotranspiration model and its associated components to obtain a reference-based SPAC model of reference evapotranspiration (R-SPAC), and it applied the model to an agricultural ecosystem. Model simulations of mean hourly ET0 were benchmarked against those of the Penman-Monteith method by the Food and Agriculture Organization (FAO-PM) throughout the growing season. The resulting good correlation obtained (R2 = 0.96, agreement index, I = 0.98, root-mean-square deviation (RMSD) = 0.05 mm h−1) validated the accuracy of the R-SPAC model. Sensitivity analysis was used to explore uncertainties and errors for ET0, T0, and E0 caused by input variables. The results showed that net radiation and shortwave radiation at the study site were the main drivers of ET0 for both the FAO-PM and R-SPAC models. The study showed that the proposed R-SPAC model can be used for predicting ET0 and for exploring interactions between climate, crop type, and soil in determining evapotranspiration under various future environment conditions.