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Integrating Remote Sensing, Flux Measurements and Ecosystem Models

Integrating Remote Sensing, Flux Measurements and Ecosystem Models. Faith Ann Heinsch Numerical Terradynamic Simulation Group (NTSG) University of Montana NCAR ASP 2007 Colloquium Regional Biogeochemistry June 12, 2007. Method Hopping. Climate gradients. Tree Rings. Historical

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Integrating Remote Sensing, Flux Measurements and Ecosystem Models

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  1. Integrating Remote Sensing, Flux Measurements and Ecosystem Models Faith Ann Heinsch Numerical Terradynamic Simulation Group (NTSG) University of Montana NCAR ASP 2007 Colloquium Regional Biogeochemistry June 12, 2007

  2. Method Hopping Climate gradients Tree Rings Historical observations Stream Flow Remote Sensing decade Inventories Eddy Flux Manipulations year Sap Flow Chambers Time scale (s) day hour Spatial scale (m)

  3. Method Hopping Remote Sensing decade Eddy Flux year Time scale (s) day hour Spatial scale (m)

  4. Eddy Covariance decade Eddy Flux year Time scale (s) day hour Spatial scale (m)

  5. Remote sensing Remote Sensing decade year Time scale (s) day hour Spatial scale (m)

  6. MODIS GPP (MOD17)

  7. Temperature VPD Stress Scalars for Light Use Efficiency Light Use Efficiency ε = εmax * m(Tmin) * m(VPD)

  8. Inputs to the MOD17 GPP/NPP Algorithm • Land Cover (MOD12Q1) • Biome Type • Annual, 1-km • 8-Day FPAR/LAI (MOD15A2) • FPAR and living biomass • 8-day, 1-km • Daily Meteorological Data (DAO) • Environmental conditions • Driving forces • Daily, 1.00 x 1.25 GPP/NPP (MOD17A2/A3)

  9. MOD17 BPLUT – v. 4.8

  10. MOD17 BPLUT – v. 4.8

  11. MODIS GPP

  12. Comparison of GPP from Terra-MODIS and AmeriFlux Network Towers Biome types used in comparison: forests (evergreen needleleaf, deciduous broadleaf, and mixed species), oak savanna, grassland, tundra, and chaparral.

  13. Calibration / Validation Tests GEOGRAPHIC PATTERNS VEGETATION: Forests, Grass, Shrubs, and Crops CLIMATE: Cold-Dry, Cold-Wet, Warm-Dry, and Warm-Wet SEASONAL PATTERNS GROWING SEASON (Start and End) STRESS (Mid-Summer Water Stress, Cold Temperatures, High Vapor Pressure Deficits) FLUX MAGNITUDE

  14. Location of the AmeriFlux network sites AmeriFlux: http://public.ornl.gov/ameriflux/ Fluxnet:http://www.fluxnet.ornl.gov/fluxnet/index.cfm

  15. Uncertainties in the MOD17 (GPP/NPP) Algorithm 1. Meteorological DAO IPAR, Temperature, VPD 2. Radiometric MODIS FPAR and LAI 3. Ecological MOD17 representation of plant physiology (BPLUT) Accurate mapping of landcover typeEach of these requires a different mode of validation.

  16. Uncertainties in the MOD17 (GPP/NPP) Algorithm 1. Meteorological DAO IPAR, Temperature, VPD 2. Radiometric MODIS FPAR and LAI 3. Ecological MOD17 representation of plant physiology (BPLUT) Accurate mapping of landcover typeEach of these requires a different mode of validation.

  17. A B Non-linear interpolation of DAO

  18. Methods of DAO Smoothing • The non-linear distances • The weighted values • The interpolated DAO variables

  19. Climate – Niwot Ridge, CO Heinsch et al. IEEE 44: 1908-1925, 2006

  20. Climate – Tonzi Ranch, CA Heinsch et al. IEEE 44: 1908-1925, 2006

  21. Global Daily Surface Meteorology vs Fluxtowers across 9 biomes From D.P.Turner et al. Remote Sensing of Env. 102:282-292. 2006

  22. Uncertainties in the MOD17 (GPP/NPP) Algorithm 1. Meteorological DAO IPAR, Temperature, VPD 2. Radiometric MODIS FPAR and LAI 3. Ecological Accurate mapping of landcover type MOD17 representation of plant physiology (BPLUT) Each of these requires a different mode of validation.

  23. MODIS LAI vs. Tower GPP for 15 Ameriflux Sites Heinsch et al. IEEE 44: 1908-1925, 2006

  24. Uncertainties in the MOD17 (GPP/NPP) Algorithm 1. Meteorological DAO IPAR, Temperature, VPD 2. Radiometric MODIS FPAR and LAI 3. Ecological Accurate mapping of landcover type MOD17 representation of plant physiology (BPLUT) Each of these requires a different mode of validation.

  25. Blodgett Forest, CA 1 = ENF 5 = Mixed Forest

  26. Gainesville, FL (Austin-Carey) 1 = ENF 2 = EBF 5 = MF 8 = Woody Savanna 12 = Cropland

  27. 4 = Deciduous Broadleaf Forest (DBF) 5 = Mixed Forest 8 = Woody Savannas Uncertainties from Land Cover (MOD12Q1) WLEF Tall Tower, Wisconsin

  28. LandCover Heinsch et al. IEEE 44: 1908-1925, 2006

  29. Daily GPP by Biome Type, July 20~27, 2001 Credit: Sinkyu Kang, NTSG

  30. MODIS GPP vs. Tower GPP (DAO met.) r = 0.859  0.173 % Error = 19%

  31. MODIS GPP vs. Tower GPP (Tower met.) r = 0.792  0.206 % Error = -2%

  32. Metolius (P. pine) Tonzi Ranch (oak savanna) Sylvania (dbf) Niwot Ridge (subalpine fir)

  33. MODIS GPP/NPP vs. Flux Towersacross 9 Biomes From D.P. Turner et al. Remote Sensing of Env 102:282-292. 2006

  34. Summary of Results • MODIS GPP follows the general trend, capturing onset of leaf growth, and in many cases, leaf senescence, while tending to over-estimate total tower GPP. • The MODIS GPP algorithm effectively captures the effects of stress events, such as late-summer dry-down, on canopies. • Substituting tower meteorological data in the MODIS algorithm leads to GPP values which are very similar to tower GPP, suggesting the algorithm adequately estimates site GPP. • If DAO meteorology and tower meteorology are similar, MODIS GPP is comparable to tower GPP. But, if the coarse-resolution DAO data is not representative of the site, MODIS GPP can differ greatly from tower GPP. • Comparisons of site data that have been received are weighted heavily towards forest biomes. Other sites need to be studied to determine if results are similar in other ecosystems.

  35. Integrating Ecosystem Process Models (e.g., Biome-BGC)

  36. Integrating Ecosystem Process Models • Does the MODIS GPP contain enough information regarding water stress? • VPD is sole water stress scalar • Soil water stress?? • Test by comparing with Biome-BGC • U.S.A. • China Mu et al., JGR, 2007

  37. Integrating Ecosystem Process Models

  38. WaterStressScalars(GrowingSeason) Mu et al., JGR, 2007

  39. Correlation between water stress scalars in Biome-BGC and MOD17(Growing Season) Mu et al., JGR, 2007

  40. Correlation between water stress scalars in Biome-BGC and MOD17(Monthly) Mu et al., JGR, 2007

  41. Correlation between Biome-BGC and MOD17 GPP Estimates(Monthly)

  42. Does MOD17 Capture Water Stress? • Water not strongly limiting for most of the wetter areas of China and the conterminous USA • m(VPD) reflects full water stress from air & soil as determined by Biome-BGC • Using only VPD underestimates the water stress in dry regions & in areas with strong monsoons • Western China, the northeast China plain, the Shandong peninsula, and the central and western United States • MOD17 overestimates GPP; add soil water stress? • Need for improved precipitation data to include soil moisture • VPD alone reflects interannual variability in most areas, • Current MOD17 adequate for global studies.

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