online_shuttleworth_wallace:   Calculation of evapotranspiration using the Shuttleworth-Wallace method

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

 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

 SAMPLE INPUT: [Parameter Ranges]     [Main Page]

Air temperature Ta (°C):  25

Mean boundary layer resistance per unit area of vegetation rb (s m-1):  25

Mean stomatal resistance rST (s m-1):  400

Projected area of leaf per unit ground area L (dimensionless):  4

Aerodynamic resistance between canopy source height and reference level raa (s m-1):  42

Aerodynamic resistance between the substrate and canopy source height ras (s m-1):  128

Surface resistance of the substrate rss (s m-1):  0

Net radiation flux into the complete crop Rn (W m-2):  400

Vapor pressure deficit at reference height D (Pa):  1000

Extinction coefficient C (dimensionless):  0.7

Atmospheric pressure P (Pa):  101325

 OUTPUT: ♦ Latent heat flux from the plant canopy λEc :  279 W m-2 ♦ Latent heat flux from the substrate λEs :  37.5 W m-2 ♦ Latent heat flux from complete crop λE :  316.5 W m-2 ♦ Evaporation from the plant canopyEc :  0.9905 cm d-1 ♦ Evaporation from the substrateEs :  0.1331 cm d-1 ♦ Evaporation from complete crop E :  1.1236  cm d-1