Time and Place Calibration of the Hargreaves Equation for Estimating Monthly Reference Evapotranspiration under Different Climatic Conditions

Ghamarnia, Houshang; Rezvani, Vahid; Khodaei, Erfan; Mirzaei, Hossein

doi:10.5539/jas.v4n3p111

Cited by 5 publications

(4 citation statements)

References 16 publications

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“…This equation is accepted by American Society of Civil Engineers (ASCE) Task Committee on standardisation of ET 0 , the International Irrigation and Drainage Committee and the food and Agriculture Organization of the United Nations (FAO) and the suitability of this equation are confirmed for different climates (Ravelli and Rota 1999;Irmak et al 2003a;Garcia et al 2004Garcia et al , 2007aZhao et al 2005;Temesgen et al 2005a;Allen et al 2005Allen et al , 2006Ge et al 2006;Lopez-Urrea et al 2006a, b;Jabloun and Sahli 2008;Gundekar et al 2008;Trajkovic and Kolakovic 2009a, b;Mohawesh and Talozi 2011;Ghamarnia et al 2012;Ravazzani et al 2012;Heydari 2014a, 2014b). The FAO-56 PM method for predicting ET 0 applied on 24-h calculation time steps has the form (Allen et al 1998) …”

Section: Pm Equationmentioning

confidence: 93%

Evaluation and calibration of Blaney–Criddle equation for estimating reference evapotranspiration in semiarid and arid regions

et al. 2014

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Penman-Monteith (FAO-56 PM) equation is suggested as the standard method for estimating evapotranspiration by the International Irrigation and Drainage Committee and FAO. On the other hand, the BlaneyCriddle (BC) temperature-based equation is an alternative and simple method compared with the FAO-56 PM equation. In the present study, the original coefficients BC equation (a and b) were calculated and calibrated spatial and temporal calibration at each station for each month based on the FAO-56 PM method for estimating reference evapotranspiration (ET 0 ) from 15 meteorological stations in central Iran (about 170,000 km 2 ) under semi-arid and arid conditions. The values of a and b in BC equation were negative and positive for all months of any station, respectively. Highest and lowest a values were obtained in December and August, respectively. December showed the lowest b values while August showed the highest. Therefore, the values of a and b were greater in cold and warm months of the year, respectively. After calibration, the root mean square error, mean bias error and percentage error values were obtained lower than 0.50, 0.015 mm day -1 and 10 % for the whole stations and months, respectively. The calibrated b values (b cal ) were proportional and inversely to the calibrated a values (a cal ). The ET 0 values based on the calibrated Blaney-Criddle equation were better than the results of the BC equation when compared to the FAO-56 PM equation as the reference model.

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Section: Pm Equationmentioning

confidence: 93%

Evaluation and calibration of Blaney–Criddle equation for estimating reference evapotranspiration in semiarid and arid regions

et al. 2014

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“…In the present study, FAO-56 PM model which has been generally referred and accepted as a standard model for estimating ET o was adopted for calibrating HS ET o model. This equation has been used to estimate ET o for so many regions and climate because of its versatility (e.g., Jerin et al 2021;Ogunrinde et al 2020b;Heydari and Heydari 2014;Ghamarnia et al 2012). The FAO-56 PM general model for estimating ET o on a daily basis is given in Eq.…”

Section: Pm Modelmentioning

confidence: 99%

Spatio-temporal calibration of Hargreaves–Samani model in the Northern Region of Nigeria

Ogunrinde

Emmanuel

Enaboifo

et al. 2021

Theor Appl Climatol

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One of the significant components of the hydrological cycle is evapotranspiration. Monthly meteorological parameters of 35 years from 19 meteorological stations across the Northern Region of Nigeria (NRN) were obtained and utilized for the calibration of Hargreaves–Samani (HS) model by comparing between potential evapotranspiration (ETo) values estimated from the original HS and the Penman–Monteith (FAO-56 PM) models. The calibrated HS equation was assessed using trend patterns and some statistical indices. The average value of root mean square error (RMSE) and the mean absolute error (MAE) decreased by 37.1 and 40%, respectively, after the calibration of the model. Also, the correlation coefficients (R) of stations that had values > 0.8 increased from 6 to 11 and the minimum R value increased by 12% above that of the original HS equation. The trend and spatial map of the statistical tests conducted also indicate better performance in most climatic regions after calibration. The precision of the HS equation improved significantly after calibration for semi-arid, humid, and sub-humid regions. However, few stations in the semi-arid, humid, and sub-humid regions did not show drastic improvement due to the peculiarity of the location and high variations in the wind speed and relative humidity parameters.

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“…of a line), obtained from the linear regression analysis between the measured and estimated values according to Ghamarnia et al (2012), as expressed in ( 11):…”

Section: Statistical Indicatormentioning

confidence: 99%

Evaluation of clearness index and cloudiness index using measured global solar radiation data: A case study for a tropical climatic region of Nigeria

Soneye¹

2020

ATM

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En este estudio se utiliza una base de datos de radiación solar de dos años (enero 2016-diciembre 2017) para modelar índices de claridad y nubosidad en Ile-Ife, Nigeria, una localidad tropical. Los análisis de variación diaria mostraron que en la mayor parte de los días la nubosidad es uniforme en el sitio de estudio, con muy pocos días extremadamente claros o nubosos. En el plano mensual, el índice de claridad fluctuó entre 0.27 y 0.51, en tanto que el índice de nubosidad varió de 0.44 a 0.72, lo cual confirma que las variaciones en ambos índices son inducidas por cambios en la posición del sol, así como por la turbidez y las nubes. Se observó que las variaciones estacionales de ambos parámetros son inversas, de manera que los incrementos en el índice de claridad favorecidos por cielos despejados y meses sin lluvia corresponden a descensos en los valores del índice de nubosidad y viceversa. Los valores mínimos del índice de claridad (0.10 y 0.28) en el sitio de estudio fueron mayores al valor mínimo (0.5) establecido para dicho índice en condiciones de nubosidad. Se desarrollaron dos ecuaciones empíricas para calcular el máximo índice de claridad a partir del índice de claridad promedio y el índice de nubosidad a partir del índice de claridad, y se sugiere su uso para locaciones con condiciones climatológicas similares al área de estudio. También se comprobó que los modelos de Hollands y Huget y de Saunier et al. tuvieron un buen desempeño, el cual mejoró en alrededor de 23.62 y 3.66%, respectivamente, después de la calibración, por lo que se consideran adecuados para su uso en otras zonas tropicales.

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Time and Place Calibration of the Hargreaves Equation for Estimating Monthly Reference Evapotranspiration under Different Climatic Conditions

Cited by 5 publications

References 16 publications

Evaluation and calibration of Blaney–Criddle equation for estimating reference evapotranspiration in semiarid and arid regions

Evaluation and calibration of Blaney–Criddle equation for estimating reference evapotranspiration in semiarid and arid regions

Spatio-temporal calibration of Hargreaves–Samani model in the Northern Region of Nigeria

Evaluation of clearness index and cloudiness index using measured global solar radiation data: A case study for a tropical climatic region of Nigeria

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