Sensitivity of Reference Evapotranspiration Computed with FAO CropWat 8.0 Model to Weather Input Variables During Two Irrigation Seasons in Kaduna, Nigeria

The sensitivity analysis of the Food and Agriculture Organization (FAO) CropWat 8.0 model is aimed at determining the dominant variable of the model in the study area. Hence, the sensitivity coefficient and the correlation of the reference evapotranspiration (ETo) in Afaka, Kaduna, Nigeria, with each of the climatic input variables of the model, namely, maximum temperature (Tmax), minimum temperature (Tmin), humidity (H), wind speed (WS) and sunshine hour (SSH), were evaluated. A perturbation method was used in the evaluation and the sensitivity coefficients were obtained in a decreasing order of 0.55, 0.42, 0.22, 0.09 and -0.08 for Tmax, WS, SSH, Tmin and H, respectively. Also, the correlation of ETo with each of the input parameters, irrespective of the others, show the following correlation coefficients, r; SSH (r = 0.8675), Tmax (r = 0.6979), Tmin (r = 0.6226), H (r = 0.19) and WS (r = 0.0742). Hence, radiation and temperature-based estimations of ETo were recommended as useful tools for ETo estimation in the face of limited or scarce data and are adaptable to areas with similar climate characteristics. This would also serve as a theoretical basis for future studies on the response of ETo to climatic change in the study area and other areas with similar climate.

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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):

Reference Evapotranspiration ◽

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.

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Empirical Equations to Estimate Evapotranspiration in Mosul City

Tikrit Journal of Engineering Sciences ◽

10.25130/tjes.27.4.10 ◽

2020 ◽

Vol 27 (4) ◽

pp. 98-102

Author(s):

Haqqi Yasin ◽

Luma Abdullah

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Air Temperature ◽

Reference Evapotranspiration ◽

Sunshine Duration ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Daily Data ◽

Daily Sunshine ◽

Measured Wind Speed

Average daily data of solar radiation, relative humidity, wind speed and air temperature from 1980 to 2008 are used to estimate the daily reference evapotranspiration in the Mosul City, North of Iraq. ETo calculator software with the Penman Monteith method standardized by the Food and Agriculture Organization is used for calculations. Further, a nonlinear regression approach using SPSS Statistics is utilized to drive the daily reference evapotranspiration relationships in which ETo is function to one or more of the average daily air temperature, actual daily sunshine duration, measured wind speed at 2m height and relative humidity

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Comparison of meteorological data, related to reference evapotranspiration, from conventional and automatic stations in the Sertão and Agreste regions of Pernambuco, Brazil

DYNA ◽

10.15446/dyna.v88n216.86372 ◽

2021 ◽

Vol 88 (216) ◽

pp. 176-183

Author(s):

Iug Lopes ◽

Miguel Julio Machado Guimarães ◽

Juliana Maria Medrado de Melo ◽

Ceres Duarte Guedes Cabral de Almeida ◽

Breno Lopes ◽

...

Keyword(s):

Reference Evapotranspiration ◽

Meteorological Data ◽

Global Solar Radiation ◽

Concordance Index ◽

Good Relationship ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Daily Scale ◽

Weather Stations ◽

Meteorological Elements

The objective was to perform a comparative study of the meteorological elements data that most cause changes in the reference Evapotranspiration (ETo, mm) and its own value, of automatic weather stations AWS and conventional weather stations CWS of the Sertão and Agreste regions of Pernambuco State. The ETo was calculated on a daily scale using the standard method proposed by the Food and Agriculture Organization (FAO), Penman-Monteith (FAO-56). The ETo information obtained from AWS data can be used to update the weather database of stations, since there is a good relationship between the ETo data obtained from CWS and AWS, statistically determined by the Willmott's concordance index (d > 0.7). The observed variations in the weather elements: air temperature, relative humidity, wind speed, and global solar radiation have not caused significant changes in the ETo calculation.

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Attributing the Changes in Reference Evapotranspiration in Southwestern China Using a New Separation Method

Journal of Hydrometeorology ◽

10.1175/jhm-d-16-0118.1 ◽

2017 ◽

Vol 18 (3) ◽

pp. 777-798 ◽

Cited By ~ 19

Author(s):

Shanlei Sun ◽

Haishan Chen ◽

Ge Sun ◽

Weimin Ju ◽

Guojie Wang ◽

...

Keyword(s):

Reference Evapotranspiration ◽

Separation Method ◽

Southwestern China ◽

Complete Analysis ◽

Physical Mechanisms ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Monthly Changes ◽

Meteorological Observations ◽

New Perspective

Abstract This study investigated monthly and annual reference evapotranspiration changes over southwestern China (SWC) from 1960 to 2012, using the Food and Agriculture Organization of the United Nations’ report 56 (FAO-56) Penman–Monteith equation and routine meteorological observations at 269 weather sites. During 1960–2012, the monthly and annual decreased at most sites. Moreover, the SWC regional average trend in annual was significantly negative (p < 0.05); this trend was the same in most months. A new separation method using several numerical experiments was proposed to quantify each driving factor’s contribution to changes and exhibited higher accuracy based on several validation criteria, after which an attribution analysis was performed. Across SWC, the declining annual was mainly due to decreased net radiation (RN). Spatially, the annual changes at most sites in eastern SWC (excluding southeastern West Guangxi) were generally due to RN, whereas wind speed (WND) or vapor pressure deficit (VPD) was the determinant at other sites. Nevertheless, the determinants differed among 12 months. For the whole SWC, increased VPD in February and decreased WND in April, May, and October were the determinant of decreased ; however, decreased RN was the determinant in other months. Overall, the determinant of the monthly changes exhibited a complex spatial pattern. A complete analysis of changes and the related physical mechanisms in SWC is necessary to better understand hydroclimatological extremes (e.g., droughts) and to develop appropriate strategies to sustain regional development (e.g., water resources and agriculture). Importantly, this separation method provides new perspective for quantitative attribution analyses and thus may be implemented in various scientific fields (e.g., climatology and hydrology).

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Analysis of seven indirect methods for evaluation of reference evapotranspiration under climate conditions of Serbia

Journal of Agricultural Sciences Belgrade ◽

10.2298/jas1801067i ◽

2018 ◽

Vol 63 (1) ◽

pp. 67-81

Author(s):

Dzenita Idrizovic ◽

Gordana Matovic ◽

Enika Gregoric ◽

Ruzica Stricevic

Keyword(s):

Reference Evapotranspiration ◽

Vegetation Period ◽

Weather Data ◽

Special Importance ◽

Climate Conditions ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Using Data ◽

Novi Sad ◽

Taylor Methods

In order to calculate water deficit of agricultural crops, it is necessary to have an insight into the evapotranspiration process. As for evaluation of reference evapotranspiration, the Penman-Monteith (FAO56-PM) method, suggested by The International Commission on Irrigation and Drainage (ICID) and Food and Agriculture Organization of the United Nations (FAO), requires several climate parameters, which are often unavailable. Thus, in this paper, the methods for computing ETo, which use limited weather data, were tested and then compared to FAO56-PM. The selected methods were those most often used as the replacement for FAO56-PM: Hargreaves, adjusted Hargreaves, Copais, Turc, Priestley-Taylor, Makkink and Hamon. ETo was calculated at the daily and average monthly levels, for the 2010-2013 period, using data from the following meteorological stations: Nis, Belgrade, Novi Sad, Loznica, Valjevo, Zlatibor, Cuprija and Kikinda. Special importance was given to the vegetation period during the dry season due to the application of irrigation. The comparison of methods was based on statistical analysis, using parameters: MXE, MAE, RMSD, ARMSD, WRMSD, b and R2. The highest rate of matching FAO-PM at the average monthly level, as well as during the 2012 growing season, was shown by Copais, Turc and Priestley-Taylor methods, thus these methods may be recommended as the replacement for FAOPM under climate conditions of Serbia. In case only temperature data are available, the results of this research justify the use of the adjusted Hargreaves equation to calculate ETo for the vegetation period.

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Combination of satellite imagery with meteorological data for estimating reference evapotranspiration

Revista de Teledetección ◽

10.4995/raet.2018.7688 ◽

2018 ◽

pp. 75

Author(s):

D. Montero ◽

F. Echeverry ◽

F. Hernández

Keyword(s):

Land Surface Temperature ◽

Land Surface ◽

Reference Evapotranspiration ◽

Meteorological Data ◽

Meteorological Station ◽

Significant Relation ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Digital Elevation ◽

Weather Stations

<p>The Food and Agriculture Organization of the United Nations (FAO) in its publication No. 56 of the Irrigation and Drainage Series presents the FAO Penman-Monteith procedure for the estimation of reference evapotranspiration from meteorological data, however, its calculation may be complicated in areas where there are no weather stations. This paper presents an evaluation of the potential of the Land Surface Temperature and Digital Elevation Models products derived from the MODIS and ASTER sensors, both on board the Terra EOS AM-1 satellite, for the estimation of reference evapotranspiration using the Penman-Monteith FAO-56, Hargreaves, Thornthwaite and Blaney-Criddle models. The four models were compared with the method proposed by FAO calculated with the observed data of a ground based meteorological station, finding a significant relation with the models Penman-Monteith FAO-56 and Hargreaves.</p>

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Prediction of solar radiation with air temperature data in a coastal location in Tamilnadu

MAUSAM ◽

10.54302/mausam.v62i1.208 ◽

2021 ◽

Vol 62 (1) ◽

pp. 85-90

Author(s):

A. MUGRAPAN ◽

SUBBARAYAN SIVAPRAKASAN ◽

S. MOHAN

Keyword(s):

Solar Radiation ◽

Air Temperature ◽

Minimum Temperature ◽

Reference Evapotranspiration ◽

Temperature Data ◽

Maximum Temperature ◽

Adjustment Coefficient ◽

Meteorological Observatory ◽

Daily Sunshine ◽

Sunshine Hour

The objective of this study is to evaluate the performance of the Hargreaves’ Radiation formula in estimating daily solar radiation for an Indian coastal location namely Annamalainagar in Tamilnadu State. Daily solar radiation by Hargreaves’ Radiation formula was computed using the observed data of maximum temperature, Tmax and minimum temperature, Tmin, sourced from the India Meteorological Observatory located at Annamalainagar and employing the adjustment coefficient KRS of 0.19. Daily solar radiation was also computed using Angstrom-Prescott formula with the measured daily sunshine hour data. The differences between the daily solar radiation values computed using the formulae were more pronounced in year around. Hence, the adjustment coefficient KRS is calibrated for the study location under consideration so that the calibrated KRS could be used to better predict daily solar radiation and hence better estimation of reference evapotranspiration.

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Evaluation of the FAO Penman–Montheith, Priestley–Taylor and Hargreaves models for estimating reference evapotranspiration in southern Malawi

Hydrology Research ◽

10.2166/nh.2012.224 ◽

2012 ◽

Vol 44 (4) ◽

pp. 706-722 ◽

Cited By ~ 23

Author(s):

Cosmo Ngongondo ◽

Chong-Yu Xu ◽

Lena M. Tallaksen ◽

Berhanu Alemaw

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Vapour Pressure ◽

Reference Evapotranspiration ◽

Climate Variables ◽

Limited Data ◽

Full Data ◽

Data Intensive ◽

Food And Agriculture ◽

Food And Agriculture Organization

This study evaluated the performance of the Food and Agriculture Organization (FAO) Penman–Monteith (PM) reference evapotranspiration (ET0) method for various limited data scenarios in southern Malawi. The study further evaluated the full data PM method against the radiation-based Priestley–Taylor (PT) and the temperature-based Hargreaves (HAG) methods, which are less data-intensive approaches commonly used to estimate ET0 in data-scarce situations. A comprehensive daily climate dataset observed at the Nchalo Sugar Estate in southern Malawi for the period 1971–2007 was the basis of the study. The results suggested that lack of data on wind speed and actual vapour pressure did not significantly affect the PM ET0 estimates. However, the estimation of radiation using various combinations of observed wind speed and relative humidity all resulted in significant deviations from the PM ET0. Further, the HAG and PT methods significantly underestimated the PM. However, the PM method computed with estimated climate variables instead of observed climate variables still outperformed both the PT and HAG methods if their original parameters and estimated radiation were used. Thus, new monthly parameters for the PT and the HAG methods are proposed for more accurate daily ET0 estimates.

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Determination of Cd, Cu, Ni and Pb in Selected rice Grain Available in Malaysia

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i4.14.27569 ◽

2019 ◽

Vol 7 (4.14) ◽

pp. 232

Author(s):

R. Abd Rashid ◽

N. A. Muda ◽

M. Saaid ◽

M. I. Abdul Halim ◽

K. Mohamed

Keyword(s):

Correlation Coefficients ◽

Mean Value ◽

World Health ◽

Local Market ◽

Rice Grain ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Rice Samples ◽

Health Organization

This study aims to determine the levels of heavy metals (cadmium, copper, nickel and lead) in imported and domestically produced rice grains sold in Malaysia market. A total of 10 brands of rice samples was purchased from the local market and analyzed using atomic absorption spectroscopy (AAS). Good linearity was observed over the range studied with a correlation coefficients (R2) of 0.9884-0.9999. The range values of the metals detected in rice grain samples were 0.67-0.8 mg/kg for cadmium, 2.14-7.0 mg/kg for copper, 1.85-2.68 mg/kg for nickel and 0.94-3.28 mg/kg for lead. The mean value of rice obtained were above the permitted level set by the Malaysia Food Act 1983 (Act 281) and Food and Agriculture Organization of the United Nations/ World Health Organization (FAO/WHO) (2015). The Provisional Tolerance Weekly Intake (PTWI) calculated were also above the prescribed limit except for copper.

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Optimal Selection of Empirical Reference Evapotranspiration Method in 36 Different Agricultural Zones of China

Agronomy ◽

10.3390/agronomy12010031 ◽

2021 ◽

Vol 12 (1) ◽

pp. 31

Author(s):

Yong Yang ◽

Rensheng Chen ◽

Chuntan Han ◽

Zhangwen Liu ◽

Xiqiang Wang

Keyword(s):

Reference Evapotranspiration ◽

Meteorological Data ◽

Aridity Index ◽

Empirical Method ◽

Climatic Conditions ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Temperature Method ◽

The Relationship ◽

Selection Of

The Food and Agriculture Organization has proposed the current version of the Penman–Monteith method (FAO56-PM) as the standard for calculating reference evapotranspiration (ET0); however, high meteorological data requirements limit its application in many areas. There is thus an urgent need to identify the best alternative empirical method to accurately calculate ET0 in regions that lack sufficient meteorological data. In this study, three temperature-based methods and five radiation-based methods were evaluated using ET0 values generated using the FAO56-PM method in 36 agricultural zones in China based on meteorological data from 823 stations, measured between 2011 and 2020. The results showed that the optimal temperature-based method and radiation-based method differed for different agricultural zones, and no one temperature method or radiation method could be suitable for all agricultural zones. The eight empirical methods were regionally calibrated to improve the ET0 calculation accuracy in the different zones. The relationship between the optimal methods and climatic conditions showed that the most reliable empirical method could be selected according to the local annual mean temperature and aridity index. The results provide useful guidance for the selection of reliable empirical ET0 methods in agricultural zones outside China.

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