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Variation of land surface albedo and its simulation

Earth Sciences Sector. Variation of land surface albedo and its simulation. Reducing Canada's vulnerability to climate change. Shusen Wang Andrew Davidson Canada Centre for Remote Sensing. Acknowledgment: CCAF, PFRA, BOREAS. Albedo and climate control surface radiation and energy balances

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Variation of land surface albedo and its simulation

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  1. Earth Sciences Sector Variation of land surface albedo and its simulation Reducing Canada's vulnerability to climate change Shusen Wang Andrew Davidson Canada Centre for Remote Sensing Acknowledgment: CCAF, PFRA, BOREAS

  2. Albedo and climate • control surface radiation and energy balances • affects boundary-layer structure and dynamics • e.g., albedo changes from forestation in temperate and boreal forest could offset C sequestration (A. Betts, 2000) Albedo and ecosystem • control microclimate conditions • affects biogeochemical cycles

  3. Variations of albedo due to • different vegetation types • snow covering • solar zenith angle …and • climate/weather impact • plant development/phenology • surface heterogeneity

  4. Precipitation in 2001 and 2003

  5. Drought impact Chapin et al. (1999): net climate-forcing due to about 5% difference in albedo between forest tundra and shrub tundra of northern Alaska are in the order of 5.5 W m-2, which is comparable to the effect of a doubling of global atmospheric CO2 concentration (4.4 W m-2, Wuebbles 1995).

  6. Temporal variation

  7. Spatial heterogeneity

  8. Local vs. Regional

  9. The albedo model 1. Based on ecosystem elements • Leaf: ref., abs., trans. • Stem/branch: ref., abs. • Snow: snow age/condition • Soil: texture, moisture 2. Ray tracing scheme for radiation transfer 3. Canopy gap probability

  10. Shortwave albedo (SSA-OA)a: leafless canopy with snow-covered groundb: leafless canopy without snow coverc: leafed canopy during growing season

  11. Reflected Radiation

  12. Direct vs. diffuse, visible vs. NIR

  13. Surface albedo and ecosystem conditionsa: stand densityb: leaf angular distributionc: leaf and wood area indicesd: leaf reflectancee: tree bark reflectancef: soil reflectance

  14. Clumping Index

  15. Net Radiation, Jul. 1998

  16. Ecological Assimilationof Land and Climate Observations- the EALCO model

  17. Summary • Drought, plant development, and spatial heterogeneity may induce significant changes of surface albedo; • Radiation transfer model based on ecosystem structure and optical parameters can better represent  dynamics; • Albedo from site measurement has limitations in spatial representation. It can be improved by the  model using RS inputs; • Dew/frost & snow interception could significantly change . Coupling with EB model is necessary to capture this phenomena; • Winter  of high latitude ecosystems is very sensitive to LAI/WAI; • Simulation at high spectral resolution can improve ecosystem C simulation.

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