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Assessment of TER and GPP using empirical models for 3 crops

CarboEurope-IP Meeting – 8-11 October 2007. Assessment of TER and GPP using empirical models for 3 crops. C. Moureaux, B. Bodson, M. Aubinet. CarboEurope-IP Meeting – 8-11 October 2007. TER assessment methods. Impacts on daily and total TER estimations.

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Assessment of TER and GPP using empirical models for 3 crops

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  1. CarboEurope-IP Meeting – 8-11 October 2007 Assessment of TER and GPP using empirical models for 3 crops C. Moureaux, B. Bodson, M. Aubinet

  2. CarboEurope-IP Meeting – 8-11 October 2007 TER assessment methods Impacts on daily and total TERestimations

  3. CarboEurope-IP Meeting – 8-11 October 2007 Data source : night-time • TERN,LT : adjustment on the whole period • TERN,ST (following Reichstein et al., 2005) 4 days 15 days

  4. CarboEurope-IP Meeting – 8-11 October 2007 Data source : daytime • TERD,LT (cf. Lee et al, 1999; Wohlfahrt et al., 2005) Intercept of the NEE-PPFD relationship fitted on a 10-day basis Daytime temperature averaged on a 10-day basis

  5. CarboEurope-IP Meeting – 8-11 October 2007 Data source : daytime • TERD,ST (modified Gilmanov et al., 2003 algorithm)

  6. CarboEurope-IP Meeting – 8-11 October 2007 GPP assessment methods During the night: GPP = 0 During the day: GPP = NEE - TER

  7. CarboEurope-IP Meeting – 8-11 October 2007 Data 3 successive crops on BE-Lon crop site : From the emergence to the harvest (or chemical haulm) SB04 WW05 P06

  8. CarboEurope-IP Meeting – 8-11 October 2007 Results • Impact of the u* threshold on TERN (using TS) • Impact of the adjustment time step (using TS) • Impact of the reference temperature (using ST model) • Impact of the data source: night- or daytime NEE (using ST model and TS)

  9. CarboEurope-IP Meeting – 8-11 October 2007 1. Results : Impact of u* threshold value

  10. CarboEurope-IP Meeting – 8-11 October 2007 1. Results : Impact of u* threshold value Daily TER [g C m-2 d-1]

  11. CarboEurope-IP Meeting – 8-11 October 2007 Results • Impact of the u* threshold on TERN (using TS) • Impact of the adjustment time step (using TS) • Impact of the reference temperature (using ST model) • Impact of the data source: night- or daytime NEE (using ST model and TS)

  12. CarboEurope-IP Meeting – 8-11 October 2007 2. Results : Impact of the adjustment time step – night-time data WW05 Daily TER [g C m-2 d-1]

  13. CarboEurope-IP Meeting – 8-11 October 2007 Results • Impact of the u* threshold on TERN (using TS) • Impact of the adjustment time step (using TS) • Impact of the reference temperature (using ST model) • Impact of the data source: night- or daytime NEE (using ST model and TS)

  14. CarboEurope-IP Meeting – 8-11 October 2007 3. Results : Impact of the reference temperature : TS or TA ? WW05 Daily TER [g C m-2 d-1]

  15. CarboEurope-IP Meeting – 8-11 October 2007 3. Results : Impact of the reference temperature : TS or TA ? Fluxes [µmol m-2 s-1]

  16. CarboEurope-IP Meeting – 8-11 October 2007 Results • Impact of the u* threshold on TERN (using TS) • Impact of the adjustment time step (using TS) • Impact of the reference temperature (using ST model) • Impact of the data source: night- or daytime NEE (using ST model and TS)

  17. CarboEurope-IP Meeting – 8-11 October 2007 4. Results : Impact of the data source SB04 Daily TER [g C m-2 d-1]

  18. CarboEurope-IP Meeting – 8-11 October 2007 Conclusions • Importance of u* threshold assessment for each crop but quite limited impact • Short term models give better daily assessment and are able to reproduce particular events • TS more reliable • Some difficulties with short term model adjustment when using the daytime measurement

  19. CarboEurope-IP Meeting – 8-11 October 2007 Objectives • Assess the impact of : • the data source : night-time or daytime data • the adjustment time step of TER models • the u* threshold value • the reference temperature : air or soil temperature on daily and total TER and GPP estimations using empirical models

  20. CarboEurope-IP Meeting – 8-11 October 2007 2. Results : Impact of the adjustment time step – daytime data • Some model adjustment problems Daily TER [g C m-2 d-1]

  21. CarboEurope-IP Meeting – 8-11 October 2007 2. Results : Impact of the adjustment time step – daytime data Daily TER [g C m-2 d-1]

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