1 / 12

Outline

Outline. Approach Data sets PAR fPAR C4/C3 LUE optimization. Approach. GPP = LUE × APAR = LUE × fPAR × PAR PAR = SW × R PB C4 and C3 LUE and fPAR algorithm. Data set: Ameriflux Site.

rodney
Télécharger la présentation

Outline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Outline • Approach • Data sets • PAR • fPAR • C4/C3 • LUE optimization

  2. Approach • GPP = LUE × APAR = LUE × fPAR× PAR • PAR = SW × RPB • C4 and C3 LUE and fPAR algorithm

  3. Data set: AmerifluxSite • Ameriflux GPP observations were used to minimize the discrepancy between modeled and observed GPP • Sites with more than one year data during 2004 to 2006 were chosen • Monthly GPP calculated from half-hourly GPP fluxes

  4. Data set: fPAR products • EVI/NDVI-derived fPAR • Monthly EVI/NDVI 2004-2006 • Original: 0.05 deg • Used in model: 0.5 deg • MODIS fPAR • Monthly MODIS fPAR 2004-2006 • Original: 0.05 deg • Used in model: 0.5 deg • SeaWifsfPAR • Monthly, 2004-2006 Jan – June • Last 6 months were restructured by monthly mean from previous years • Original: 0.25 deg • Used in model: 0.5deg

  5. Data set: radiation • GEOS-5 surface net shortwave radiation and surface albedo • 3-hourly; 2004 – 2006; 2×2.5 deg • SRB PAR and SW • Monthly; 2004-2006; 1 deg • CERES PAR and SW • Monthly; 2004-2005; 1 deg • BSRN measured SW • Monthly; 2004-2005

  6. Data set: C4 distribution • Global C4 percentage • 1 deg • Africa C4 percentage • 1 km

  7. EVI/NDVI-derived fPAR • Area distribution of global EVI according to biome types • Linear function applied to covert EVI/NDVI to fPAR • Upper bound: top 25% EVI of topical rainforest • Lower bound: EVI in Sahara desert with annual rainfall less than 25 mm

  8. PAR • Adjustment for GEOS-5 shortwave radiation • Downward SW = net SW / ( 1 - albedo ) • Ratio of SRB SW to GEOS SW • Conversion from shortwave radiation to PAR • Ratio of SRB PAR to SRB SW • High temporal resolution PAR using GEOS-5 adjusted SW

  9. APAR = PAR × fAPR

  10. C4 photosynthesis • Algorithm A • Same fPAR for C3 and C4 • Separate APAR according to C3 and C4 spatial distribution • Algorithm B • Allocate most of the fPAR seasonal cycle to C4 • Separate APAR with different fPAR for C3 and C4

  11. C4 LUE • Lobell ratio: • Mean C4 LUE: 0.66 g C/MJ • Mean C3 LUE: 0.29 g C/MJ • Ameriflux ratio: • Cropland rotation sites • Mean C4 GPP/mean C3 GPP = 1.32

  12. LUE optimization • A range of LUE was used to calculate GPP using the paradigm: GPP = LUE × APAR • Just account for monthly GPP from all C3 sites and rotation site with C3 crops • C4 LUE calculated from the Lobell and Ameriflux ratios

More Related