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1、 Build the Model Build the Model ETins = Rn - G - HRn GH ETins Graph from Allen, et. al., (2002) Build the Model NDVI=f(reflectance)H=f(NDVI, temperature, reflectance, solar radiation, wind speed)G=f(NDVI, solar radiation, reflectance) End Start ETins=Rn-H-GOutput daily ETGeneral flowchart Rn=f(Rs,
2、reflectance) Build the ModelSatellite inputs: surface temperature and reflectance. Local weather inputs: solar radiation, humidity and wind speed =0.484 1+ 0.3353 -0.3245 +0.551 6 +0.3058 -0.376 9-0.0015i Build the Model y = -2.6955x4 + 3.9817x3 - 1.6401x2 - 0.1102x + 0.4079 R2 = 0.6633 0 0.1 0.2 0.
3、3 0.4 0.5 0.6 0 0.2 0.4 0.6 0.8 1 NDVI C Build the Model H = (r cp dT) / rah HrahdTrah = the aerodynamic resistance to heat transport (s/m).z1z2dT = the near surface temperature difference (K). Graph from Allen, et. al., (2002) Build the Modelrah=ln(z2/z1)/(u* k)u*= friction velocity Ts=303 KTs=323
4、KBuild the Model Build the Model dT regression Build the Model Build the Model StartCalculate friction velocity (u*) at weather station and use to get wind speed at 200m Calculate roughness length( z om) for each pixel from NDVICalculate dT for each pixel from TsCalculate friction velocity ( u*) for
5、 each pixelCalculate rah for each pixel Calculate H for each pixelCalculate stability parameter for each pixelUpdate H for each pixel based on stability parameter and iterate till change in H less than 10%End Build the Model Calculate Et from energy balance ETrins)ETrdaily)ETdaily=ETins/ ETrinsETrda
6、ily Build the Model Pecan orchardAlfalfa fieldBuild the Model Li Cor systemValidate the Model mm/dayValidate the Model Validate the Model The data represent no cover, partial leaf cover and closed canopy.Average of relative error all days 11% with the greatest % error when Et was small in the winter
7、 and early spring. Average error Validate the Model Sensitivity analysis dT regression Build the Model dT is linearly related to Ts, H=f(dT, rah, u*, L, Zom)Sensitivity analysis 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 dT (K) ET ( mm /d ay ) Full vegetation Little vegetation Half vegetation Sensitivity analy
8、sis Sensitivity analysis 0 1 2 3 4 5 6 7 8 500 600 700 800 900 1000 1100 1200 Rs (w/m2) ET ( mm /d ay ) Full vegetation Little vegetation Half vegetation Sensitivity analysis 0015.0367.0305.0 551.0324.0335.0484.0 98 6531 0 1 2 3 4 5 6 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Albedo ET ( mm /d ay ) Full vegeta
9、tion Little vegetation Half vegetation Sensitivity analysis Sensitivity analysis 0 1 2 3 4 5 6 7 8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 C (Rn/G) ET ( mm /d ay ) Full vegetation Half vegetation Little vegetation Sensitivity analysis ah Sensitivity analysis 0 1 2 3 4 5 6 7 0 20 40 60 80 100 rah (s/m) ET ( mm /d ay ) Full vegetation Little vegetation Half vegetation ah Sensitivity analysis
SEBAL-Sensitivity-NewMexicoStateUniversitySEBAL靈敏度-新墨西哥州立大學(xué)
