online_shuttleworth_wallace:   Calculation of evapotranspiration using the Shuttleworth-Wallace method


Solar evaporator at Red Rock Ranch, Panoche Water District, Fairbaugh, California
Solar evaporator at Red Rock Ranch, Panoche Water District, Fairbaugh, California


References:

Formulas
Δ = (0.00815 Ta + 0.8912)7

rac = rb /(2L)

rsc = rST /(2L)

Ra = (Δ + γ) raa

Rs = (Δ + γ) ras + γrss

Rc = (Δ + γ) rac + γrsc

Rns = Rn e-CL

A = Rn - 0.2Rns

As = 0.8Rns

Cc = 1 / {1 + (Rc Ra) / [Rs (Rc + Ra)]}

Cs = 1 / {1 + (Rs Ra) / [Rc (Rs + Ra)]}

PMc = [ΔA + (ρacpD - ΔracAs) / (raa + rac)] / [Δ + γ {1 + rsc/(raa + rac)}]

PMs = [ΔA + (ρacpD - Δras(A - As) / (raa + ras)] / [Δ + γ {1 + rss/(raa + ras)}]

λEc = Cc PMc

λEs = Cs PMs

λE = λEc + λEs


INPUT DATA:
       [Sample Input]      [Parameter Ranges]

Air temperature Ta (°C):    

Mean boundary layer resistance per unit area of vegetation rb (s m-1):    

Mean stomatal resistance rST (s m-1):    

Projected area of leaf per unit ground area L (leaf area index) (dimensionless):    

Aerodynamic resistance between canopy source height and reference level raa (s m-1):    

Aerodynamic resistance between the substrate and canopy source height ras (s m-1):    

Surface resistance of the substrate rss (s m-1):    

Net radiation flux into the complete crop Rn (W m-2):    

Vapor pressure deficit at reference height D (Pa):    

Extinction coefficient C (dimensionless):    
Leave blank to set default C = 0.7

Atmospheric pressure P (Pa):    
Leave blank to set default at sea level, P = 101325

Please enter input data and press 'Calculate'.

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