Table 1.

The original form of the 13 empirical models associated with the input parameters.

Sl. no.	Models	Models input	Equations	Proposed by
Temperature-based
ETo,1	Hargreaves–Samani	Ra, Tave, Tmax, Tmin	ET0,1 = [0.0023 × Ra (Tave + 17.8) (Tmax − Tmin)0.5]/λ	Hargreaves and Samani13
ETo,2	Hargreaves M1	Ra, Tave, Tmax, Tmin	ET0,2 = [0.408 × 0.0030 × (Tave + 20) (Tmax − Tmin)0.4 × Ra	Hargreaves and Samani13
ETo,3	Hargreaves M2	Ra, Tave, Tmax, Tmin	ETo,3 = $0.408\times 0.0023\times \left(T,a,v,e,+,17.8\right)\times {(T_{\mathit{max}}-T_{\mathit{min}})}^{0.424}\times R_a$	Hargreaves and Samani13
ETo,4	Berti	Ra, Tave, Tmax, Tmin	ET0,3 = $\left[0.00193,R,a,\left(T_{\mathit{ave}},+,17.8\right),{\left(T_{\mathit{max}},-,T_{\mathit{min}}\right)}^{0.517}\right]$/λ	Bertiet al.56
Mass transfer-based
ETo,5	WMO	U2, es − ea	ET0,4 = (0.1298 + 0.0934U2)(es − ea)	WMO30
Radiation-based
ETo,6	Abtew	Rs, Tmax	ET0,5 = $\frac{1}{56}\frac{R_s{T}_{\mathit{max}}}{\lambda }$	Abtew51
ETo,7	Irmak1	Rs, Tave	ET0,6 = $0.149R_s+0.079Tave-0.611$	Irmak et al.53
ETo,8	Irmak2	Rn, Tave	ETo,7 = 0.489 + 0.289 Rn + 0.023 Tave	Irmak et al.53
ETo,9	Makkink	Rs, Tave	ET0,8 = $0.61\frac{1}{\mathrm{\lambda }}\left[\frac{\mathrm{\Delta }}{\mathrm{\Delta }+\mathrm{\gamma }}\right]{\mathrm{R}}_{\mathrm{s}}-0.12$	Makkink54
ETo,10	Priestley-Taylor	Rn, Tave	ET0,9 = $1.26\left[\frac{\mathrm{\Delta }}{\mathrm{\Delta }+\mathrm{\gamma }}\right]\left({\mathrm{R}}_{\mathrm{n}},-,\mathrm{G}\right)/\mathrm{\lambda }$	Priestley and Taylor55
ETo,11	Jensen–Haise	Rs, Tave	ET0,10 = $(0.025\mathrm{Tave}+0.08)\frac{{\mathrm{R}}_{\mathrm{s}}}{\mathrm{\lambda }}$	Jensen and Haise52
ETo,12	Tabari	Rs, Tmin, Tmax	ET0,11 = 0.156Rs—0.0112Tmax + 0.0733Tmin—0.478	Tabari et al.40
ETo,13	Turc	Rs, Tave	ETo,13 = 0.013 $\frac{T_{\mathit{ave}}}{T_{\mathit{ave}}+15}(Rs+50)$	Turc57

T_ave, T_max, and T_min are the mean (average), maximum, and minimum temperature (°C), respectively and λ is the latent heat of vaporization (2.45 MJ kg⁻¹), ${\mathrm{a}}_{\mathrm{w}}=0.3+0.58\exp \left[-,{\left(\frac{\mathrm{J}-170}{45}\right)}^2\right]$ and ${\mathrm{b}}_{\mathrm{w}}=0.32+0.54\exp \left[-,{\left(\frac{\mathrm{J}-228}{67}\right)}^2\right]$ (after Peng et al.¹¹).