online_shuttleworth_wallace:   Calculation of evapotranspiration using the Shuttleworth-Wallace method Solar evaporator at Red Rock Ranch, Panoche Water District, Fairbaugh, California References: Aguilar, R. D., and V. M. Ponce. 2013. Evapotranspiration using the Shuttleworth-Wallace method. Shuttleworth, J. W., and J. S. Wallace. 1985. Evaporation from sparse crops-an energy combination theory, Quarterly Journal of the Royal Meteorological Society, III, 839-855. 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 canopy Ec :  0.9905 cm d-1 ♦ Evaporation from the substrate Es :  0.1331 cm d-1 ♦ Evaporation from complete crop E :  1.1236  cm d-1