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TABLE OF CONTENTSPageList of Symbols 4List of Figures 6Introduction 71. Background2. Concept3. Objectives4. Who can use this manual?The Theoretical Basis of SEBAL1. Overview – How SEBAL computes evapotranspiration (ET) 92. Data requirements and data preparation 11A. Cloudy conditions 11B. Header file information 12C. Land-use map 12D. Weather data 12The Operation of the SEBAL Model1. Setting up the image 142. Acquiring header file information, weather data, and reference ET values 143. Surface radiation balance equation 14A. Surface albedo 16B. Incoming shortwave radiation 19C. Outgoing longwave radiation 19D. Choosing the “cold” and “hot” anchor pixels 23E. Incoming longwave radiation 23F. Solving the surface energy balance equation 244. Surface energy budget equationA. Soil heat flux 24B. Sensible heat flux 25C. Latent Heat Flux, λET, Instantaneous ET, and ET r Fraction 345. 24-hour evapotranspiration 356. Seasonal evapotranspiration 38Appendices 401. Acquiring header file information2. Land-use map and momentum roughness length3. Reference evapotranspiration calculation4. Preparing the original satellite image for use in SEBAL5. Time issues around weather data and reference evapotranspiration2
6. Tables for surface albedo computations7. Methods for selecting “cold” and “hot” pixels8. Iteration spreadsheet used for the atmospheric stability correction9. SAVI and LAI for southern Idaho10. G/R n computations for water surfaces and snow11. The stability of the atmosphere12. The SEBAL Mountain Model3
Page 1: SEBALSurface Energy Balance Algorit
Page 5 and 6: δ declination of the earth radians
Page 7 and 8: INTRODUCTION1. BACKGROUNDLand manag
Page 9 and 10: THE THEORETICAL BASIS OF SEBAL1. OV
Page 11 and 12: The surface emissivity is the ratio
Page 13 and 14: • Reference evapotranspiration, E
Page 15 and 16: Figure 3. Flow Chart of the Net Sur
Page 17 and 18: 2. The reflectivity for each band (
Page 19 and 20: and ET are specified for the two ex
Page 21 and 22: To complete step 2, model F06_surfa
Page 23 and 24: D. Choosing the “Hot” and “Co
Page 25 and 26: irrigated crops near Kimberly, Idah
Page 27 and 28: where; u * is the friction velocity
Page 29 and 30: Weather stationu, z x, z om, u *H f
Page 31 and 32: Note: An alternative method used by
Page 33 and 34: where;⎛ 2 ⎞⎜1+ x(0.1m)Ψ = 2
Page 35 and 36: where; ET inst is the instantaneous
Page 37 and 38: Figure 6 shows an example of a dail
Page 39 and 40: 1. If there is some cloud cover in
Page 41 and 42: • For all other formats (includin
Page 43 and 44: On the main page, select Type in Pa
Page 45 and 46: These values for z om can vary by r
Page 47 and 48: Appendix 3Reference Evapotranspirat
Page 49 and 50: and click on “Open”3. Provide t
Page 51 and 52: 5. Describe weather station and wea
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8. Save the output file using a nam
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4. Go to the Viewer tool and view t
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Appendix 5Time Issues Around Weathe
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2. What time interval does the data
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The wind speed is 3.4 m/s for the 1
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Table 6.3. ESUN λ for Landsat 5 TM
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Table 6.6. Typical albedo values.Fr
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4. Make a first guess for T cold by
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Fig.3. P40/R30, Landsat 7 ETM+ 4/8/
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Fig.5. P40/R30, Landsat 7 ETM+ 4/8/
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We open the image or subset image a
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Now, we look at the northwest area
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(2) The regional weather or soil co
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We conclude that this “heat islan
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Part 1: using the manual iteration
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Part 2: Using the automatic iterati
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Appendix 9SAVI and LAI for Southern
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equation for G. The following are e
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and for 24-hours:Gwater = 0.9 Rn -
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The Stability of the AtmosphereAppe
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Appendix 12The SEBAL Mountain Model
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where; t is the standard clock time
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N. Momentum Roughness LengthThe mom
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