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CLASSIC –AMMA Fieldwork 2005/2006 and modelling activities

CLASSIC –AMMA Fieldwork 2005/2006 and modelling activities. Jon Bennie, Claire Damesin, Josiane Seghieri and Lina Mercado. Outline. Motivation and objectives About the JULES model CLASSIC –CESBIO measurements What have we learned from measurements

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CLASSIC –AMMA Fieldwork 2005/2006 and modelling activities

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  1. CLASSIC –AMMA Fieldwork 2005/2006 and modelling activities Jon Bennie, Claire Damesin, Josiane Seghieri and Lina Mercado

  2. Outline • Motivation and objectives • About the JULES model • CLASSIC –CESBIO measurements What have we learned from measurements Model evaluation using physiological measurements • 2006 Fieldwork campaign

  3. Aim: To collect physiological and environmental data to improve the performance of land-surface models, particularly JULES (The Joint UK land atmosphere simulator) in arid environments. Objectives: Evaluate the sensitivity of plant physiological processes to temporal and spatial variations in climate.Sensitivity analysis – what parameters are most important in constraining fluxes in the land surface scheme?

  4. Campaign (2005/2006) objectives: • Characterise diurnal cycle and spatial variability of surface temperatures (soil and plants) and soil moisture. • Characterise diurnal cycle of Photosynthesis and stomatal conductance – interspecies comparison under the same conditions. • Changes in leaf area index and plant fractional coverduring the measuring period.

  5. What did we measure? Leaf level measurements on herbaceous and woody plants • Diurnal cycles of: • Photosynthesis and transpiration (IRGA) • Stomatal conductance (porometer, IRGA) • Leaf water potential • (pressure chamber) • Characterisation of species leaf-level response to light and temperature (IRGA).

  6. What did we measure? Soil and leaf temperatures : Tsoil :bare soil, soil under vegetation Tvegetation: sun/shade leaf herbaceous woody plants Tstems Soil moisture -Sampled within the flux tower footprint - Within a 1km transect

  7. What did we measure? Continuous surface and sub-surface temperatures and soil moisture

  8. What did we measure? LAI , fractional cover and vegetation classifications (CESBIO protocols)

  9. 18.08.05 14.08.05 What have we learned ? The sun Team

  10. C3 C3 C3 Tragus Alysicarpus Cenchrus Zornia Dact. Balanites Comb. Y Comb. A Comparison of Gs and LWP among C3 and C4 species 12/08/05 13/08/05 15/08/05

  11. The ‘shade’ Team

  12. Transect sampling of surface temperature 11th Aug. 05 herbs Sampling along 1 km transects within the footprint of the flux tower bare soil

  13. JULES The Joint UK Land Environment Simulator (JULES), based on MOSES, the original land surface scheme of the Hadley Centre GCM.JULES is being developed with regular “official” releases (currently JULES v.1.0) and a modular structure.The flexible structure is intended to allow it to be modified and developed by the community to suit different requirements, spatial scales (from flux-tower to global models) and complexity.

  14. Assessing JULES

  15. Surface conductance Gross primary productivity JULES runs using Agoufou met data. August 14th 2005. Evapotranspiration

  16. Preliminary analysis suggests: • Current JULES parameterisation of the Farquhar model of photosynthesis for C3 plants leads to much lower gsthan observed in leaf-level field measurements. • We expect an underestimation of water fluxes from the landscape even when C3 plants are not the dominant functional type. • e.g. If the ratio of C3/C4 cover is 0.35, mean daily error for July-August 2005 water flux would be 25%. • Full sensitivity analysis of JULES to soil and plant physiological parameters at the site is planned.

  17. Fieldwork campaign 2006 • Continue measurements initiated in 2005 • Further diurnal cycles of physiological variables • stomatal conductance and photosynthesis • Complete data-set of leaf-level responses for dominant woody and herbaceous species at the site – temperature, PAR, CO2, soil moisture. • Continuous surface measurements (IRT) and (transects within tower flux print and 1km) Soil moisture • Plant and soil temperature

  18. Fieldwork campaign 2006 • Possible new measurements in 2006 (to discuss) • Within the flux foot print • Leaf optical properties Measurements of reflectance and transmittance to infer leaf absorptance (possible use of Field spectroradiometer) • Soil properties Bulk density/porosity; soil moisture release data Heat conductivity and heat capacity Water potential/water content curve

  19. Aknowledgements Valerie Le Dantec, Eric Mougin,Frank Timouk, Francois Lavenu, Francoise Guichard, Laurent Kergoat,Colin Lloyd, Chris Taylor, Caroline Bain, Caroline Houldcroft,Frederic Baup, Alexi Berg, Richard Dupont,Amusthapha Traore, Amusthapha , Yacuba,Taraweti

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