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The 2005 Nocturnal Boundary Layer Experiment The CO2 side of it.

The 2005 Nocturnal Boundary Layer Experiment The CO2 side of it. Starring Caroline Bain, Françoise Guichard Frédéric Baup, Laurent Kergoat, Yacouba Traore and Chris ‘Bekham’ Taylor with data from C. Lloyd, F. Lavenu, F. Timouck, V. Le Dantec P de Rosnay E Mougin , P Hiernaux and others.

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The 2005 Nocturnal Boundary Layer Experiment The CO2 side of it.

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  1. The 2005 Nocturnal Boundary Layer Experiment The CO2 side of it. Starring Caroline Bain, Françoise Guichard Frédéric Baup, Laurent Kergoat, Yacouba Traore and Chris ‘Bekham’ Taylor with data from C. Lloyd, F. Lavenu, F. Timouck, V. Le Dantec P de Rosnay E Mougin , P Hiernaux and others

  2. Objectives 1) Obtain large scale surface fluxes of CO2 2) Document near surface atmosphere (mixing, monsoon flux, low level jet) Method : on calm night, no wind, no turbulence, no vertical mixing CO2 from the surface accumulates in the first meters of air. Using the atmosphere as a giant ‘cuvette’ How : mass balance of CO2 from CO2 vertical profiles during the same night Method used in Brasil, Canada.

  3. Material Balloon PTU sonde Vaisala sonde plugged to the PTU data radio-transmitted Protocole : as many profiles as possible

  4. Results about 100 profiles from 7/08 to 22/08 a few nights suitable for CO2 (too windy, squall line arriving, technical failures) CO2 data processed as of April 2006 : 14/08 15/08 17/08 CO2 Golden day 18/08

  5. 17/08/2006 Large accumulation over night Inversions, CO2, wind (jet) very consistent

  6. Surface Flux = 5.1 mmol/m2/s u* around 0.01

  7. 120 km MODIS NDVI. Orange = « bare » soil

  8. 120 km 25.5 mm Kobou 16 08 2005 2h45

  9. 14/08 F=2.0 15/08 F=4.6 18/08 F=3.7

  10. Conclusions Vaisala carbocap+radio : great ! (Agoufou world record 700m) Confirms 2004 high fluxes : order of 4-5 mmol/m2/s 2005 = windy. Typical scenario : Jet starts, increases (speed and depth) see typical night og August 11th On windy nights, shear driven turbulence creates ‘leaks’ of the ‘cuvette’. How much ? Sometime LLJ strong enough to mix the air completely. u* and richardson number filtering/parameterizing ? Links with Low Level Jet : Is it a barrier for CO2 ? (some say yes our feeling is hum… interesting …) Would L.E.S help ? We’d like to try some. Some more processing to be done, and writing.

  11. Perspectives 2006 No more night-time fluxes (habana !) Field trip in Benin, Mali, (july/september). Objective : try day-time Boundary Layer budgets method : measure height of boudary layer + [CO2], T, Rv in the CBL. Benin : Zi from profiler, UHF etc… [CO2] from kite (?) Mali : Zi from balloon (2.5 km !). Might be last balloon campaign

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