scholarly journals Regional Calibration of Hargreaves Equation in the Xiliaohe Basin

2016 ◽  
Vol 04 (07) ◽  
pp. 28-36
Author(s):  
Leizhi Wang ◽  
Qingfang Hu ◽  
Yintang Wang ◽  
Yong Liu ◽  
Lingjie Li ◽  
...  
Keyword(s):  
Hargreaves Equation

scholarly journals FAO-56 Penman-Monteith DailyETofrom Linear Regression Calibrated Hargreaves Equation with Wind Terms in Tropics with Limited Data

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Eric Kra
Keyword(s):  
Linear Regression ◽  
Quadratic Function ◽  
Constant Term ◽  
Calibration Method ◽  
Temperature Data ◽  
Limited Data ◽  
Wide Range ◽  
Hargreaves Equation ◽  
Historical Temperature ◽  
Monteith Equation

Hargreaves equation (HG), which lacks a wind speed (u2) term, was modified, through a linear regression calibration method, into LHGu which hasu2terms. LHGu is effectively a simplified method for approximating FAO-56 Penman-Monteith equation (FPM) daily reference evapotranspiration (ETo) in tropics with only temperature data. In LHGu, the “0.0023” constant term in HG was calibrated as a shifted power function ofu2, and the calibration constant was parametrized as a quadratic function ofu2. LHGu was developed using simulated constantu2data and historical temperature data for four sites in West Africa: Abidjan, Accra, Daloa, and Lome. LHGu matched FPMETobetter than HG over a wide range ofu2: for Accra, foru2range 0.5–6.0 m/s, the modified coefficient of efficiency,E1, varied narrowly (0.83–0.98) for LHGu but widely (0.14–0.95) for HG optimized foru2=2.0 m/s; the corresponding MBE ranges were −0.05–0.01 mm/d for LHGu and 0.02–0.63 mm/d for HG which cannot respond to varying dailyu2. LHGu is useful for quickly computing practically accurate estimates of FPMETofor varying dailyu2where only temperature data are available.

Characteristics of Reference Evapotranspiration of Wetland Based on Penman-Monteith and Hargreaves Methods

2012 ◽  
Vol 610-613 ◽  
pp. 3013-3016
Author(s):  
Xiang Hu Li ◽  
Qi Zhang ◽  
Yun Liang Li
Keyword(s):  
Correlation Coefficient ◽  
Direct Measurement ◽  
Water Depth ◽  
Water Loss ◽  
Strong Correlation ◽  
Reference Evapotranspiration ◽  
Relative Importance ◽  
Monthly Means ◽  
Different Types ◽  
Hargreaves Equation

Evapotranspiration (ET) constitutes the dominant water loss from many different types of wetlands. The relative importance of ET is apparent in its influence over water depth, temperature and salinity. However, direct measurement of ET, especially for wetland, is difficult, costly, and rarely available. In this study, the Penman-Monteith model was selected to estimate the reference evapotranspiration for short and tall canopies, moreover, Hargreaves equation was also used to simulate the ETref and test the precision of Penman-Monteith method. The results show that the reference evapotranspiration are maximal between June and August and minimal in winter, and ETrs is larger than ETos in the whole simulation periods. H ET0 and ETos have the same variation trend, but the former was smaller than the latter during May to September. Finally, there is a strong correlation between ETos and ETrs, with the correlation coefficient are 0.98 and 0.99 at daily and monthly means scale.

Calibration and spatial modelling of daily ET0 in semiarid areas using Hargreaves equation

2017 ◽  
Vol 11 (3) ◽  
pp. 325-340 ◽  
Author(s):  
Francisco Gomariz-Castillo ◽  
Francisco Alonso-Sarría ◽  
Francisco Cabezas-Calvo-Rubio
Keyword(s):  
Spatial Modelling ◽  
Semiarid Areas ◽  
Hargreaves Equation

Regional calibration of Hargreaves equation for estimating reference ET in a semiarid environment

2006 ◽  
Vol 81 (3) ◽  
pp. 257-281 ◽  
Author(s):  
P. Gavilán ◽  
I.J. Lorite ◽  
S. Tornero ◽  
J. Berengena
Keyword(s):  
Semiarid Environment ◽  
Hargreaves Equation ◽  
Reference Et

scholarly journals Statistical analysis of modified Hargreaves equation for precise estimation of reference evapotranspiration

2021 ◽  
Vol 73 (1) ◽  
pp. 1-12
Author(s):  
Rimsha Habeeb ◽  
Xiang Zhang ◽  
Ijaz Hussain ◽  
Muhammad Zaffar Hashmi ◽  
Elsayed Elsherbini Elashkar ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Reference Evapotranspiration ◽  
Precise Estimation ◽  
Hargreaves Equation

Variations and Sensitivity Analysis of Reference Evapotranspiration During 2010-2019 in the Zhangye Farmland Oasis, Northwest China

2021 ◽  
Author(s):  
Miao Fang
Keyword(s):  
Sensitivity Analysis ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Northwest China ◽  
Meteorological Factor ◽  
Maximum Temperature ◽  
Regression Equations ◽  
Significance Level ◽  
Hargreaves Equation ◽  
Increasing Trends

Abstract Reference evapotranspiration (ET0) is an important parameter for agricultural water management in the arid Zhangye farmland oasis. However, the ET0 variations in this oasis over the last decade and meteorological forcings of these variations are unknown. This study investigated the ET0 variations during 2010-2019 in this oasis using the FAO-56 Penman-Monteith (PM) and Hargreaves equations. Results showed that the ET0 features daily and monthly variations with peak values in mid-July and an annual cycle. Although the estimated ET0 series based on the two equations have high correlations in the time domain, the Hargreaves equation always underestimates the ET0 compared to the PM equation. The yearly ET0 showed statistically significant increasing trends (90% significance level) during 2010-2019, while statistically significant increasing trends in monthly ET0 are found only in March and November. Increasing trends reflected in monthly and yearly ET0 are mainly attributed to the increasing maximum temperature and sunshine duration and decreasing relative humidity. Sensitivity analysis demonstrated that the meteorological factor to which the ET0 is most sensitive varies with time scale and equation. Moreover, regression equations used to correct the underestimation associated with the Hargreaves equation for estimating ET0 in the Zhangye farmland oasis also were constructed.

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