1 / 20

Advective effects on short term and long term Net Ecosystem Exchange

Advective effects on short term and long term Net Ecosystem Exchange C. Feigenwinter 1 , C. Bernhofer 2 , R. Vogt 1 , T. Grünwald 2 , U. Eichelmann 2 , H. Prasse 2 , U. Postel 2 1 University of Basel, Institute of meteorology, climatology and remote sensing

mac
Télécharger la présentation

Advective effects on short term and long term Net Ecosystem Exchange

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. Advective effects on short term and long term Net Ecosystem Exchange C. Feigenwinter1, C. Bernhofer2, R. Vogt1 , T. Grünwald2, U. Eichelmann2, H. Prasse2, U. Postel2 1 University of Basel, Institute of meteorology, climatology and remote sensing 2 TU-Dresden, Institute of hydrology and meteorology

  2. Overview Advective effects on short term and long term Net Ecosystem Exchange C. Feigenwinter1, C. Bernhofer2, R. Vogt1 , T. Grünwald2, U. Eichelmann2, H. Prasse2, U. Postel2 1 University of Basel, Institute of meteorology, climatology and remote sensing 2 TU-Dresden, Institute of hydrology and meteorology • Site overview • Results and conclusions MORE I • Experimental setup MORE II (More measurements in the ORE mountains) • Short theory and methodology • Results MORE II • effects of advective fluxes on NEE • Conclusions and outlook

  3. Site overview Elevation Landuse Inclination Exposition Overview anchor station Tharandter Wald 50°58‘ N, 13°34‘ E 375 m a.s.l. Annual mean temp. 7.7° Annual mean precip. 819 mm

  4. MORE I Results from MORE I (2001, DOY 263-283) (Feigenwinter et al., 2004, Boundary-Layer Meteorol., in press) -----EC + storage change  + advection terms difference: 0.18 g C m-2 d-1 (10 %)

  5. MORE I Conclusions from MORE I • Methododical problems and deficits for evaluation of the advection terms (i.e. vertical profiles of wind velocity, CO2 concentrations and horizontal concentration gradients are strongly dependent on the experimental design) • Short duration of the MORE I experiment does not allow conclusions that are generally valid. Results have to be confirmed and/or adjusted by long term measurements. • Results published in: • Feigenwinter, C., Bernhofer, C. and Vogt, R. (2004): The influence of advection on the short term CO2 budget in and above a forest canopy, Boundary-Layer Meteorology, in press. • MORE II Long term study (growing season) Experimental setup essentially improved Optimised coordination between measurements (gradients, wind profile, sampling rates) Adaptation of the permanent measurements according to the task

  6. Experimental setup: Situation Experimental setup situation MORE I : Sep/Oct 2001 height (trees)26 m (P2, P3) MORE II: Mai/Oct 2003 height (towers) 30 m (P1, P2, P3)

  7. Experimental setup MORE II Experimental setup: Instrumentation

  8. Experimental setup: Tower P1

  9. Experimental setup: Tower P2

  10. Experimental setup: Tower P3

  11. Theory and methodology Experimental evaluation of CO2 exchange in a forest ecosystem I source/sink of c II storage change III turbulent flux(EUROFLUX, Aubinet et al., 2000; FLUXNET, Agr. For. Met. Vol. 113, 2002) IV vertical advection(Lee, 1998; Baldocchi, 2000) V horizontal advection(Aubinet et al., 2003, Staebler and Fitz-jarrald, 2004; Feigenwinter et al., 2004)

  12. Theory and methodology Estimation of the mean vertical wind component: sinusoidal fit over a sufficiently long period(Lee, 1998; Baldocchi et al., 2000; Paw U et al. (2000))or „planar fit“(Wilczak et al., 2001) Theory und methodology non turbulent advection terms vertical advection

  13. Theory and methodology Theory und methodology non turbulent advection terms vertical advection ● tower P1 (30 m) ● tower P2 (30 m) ● tower P3 (30 m) ● main tower (anchor station) Estimation of the mean CO2 concentration in the volume below the reference level: and log-square fit of the concentration profiles

  14. Theory and methodology Theory und methodology non turbulent advection terms horizontal advection __ sonics__cup anemometer ___ measured gradient

  15. Results MORE II positive during nighttime with large scatterzero during daytime Results non turbulent advection terms vertical advection

  16. Results MORE II Theory und methodology non turbulent advection terms horizontal advection • Flow conditions during MORE II (DOY 155-285) • mainly from SW – W – NW • - no distinct drainage flow at night

  17. Results MORE II Theory und methodology non turbulent advection terms horizontal advection • Distribution of horizontal concentration gradients during MORE II (DOY 155-285) • large in the lower trunk space at night • - main direction NE – E - SE

  18. Results MORE II Theory und methodology non turbulent advection terms horizontal advection • Horizontal advection MORE II (DOY 155-285) • large in the lower trunk space at night, large scatter • positive (source term)! • - zero during daytime Fluxes for a layer thickness of 1 m at the resp. height  0.5 m  2.0 m  8.0 m  20.0 m  30.0 m

  19. Results MORE II Theory und methodology non turbulent advection terms horizontal advection • Horizontal advection MORE II (DOY 155-285) • large in the lower trunk space at night • positive (source term)! • - small during daytime

  20. Conclusions and outlook Conclusions and outlook • Vertical and horizontal advection are in the same order of magnitude as the turbulent EC-flux of CO2 • The large scatter of the mean advection terms is the result of a large day to day variability • Including the advection terms into the NEE equation significantly increases the nightly CO2 source and thus reduces the Carbon sink of the forest • There are still many methododical problems and only a few studies for comparison. The presented results may therefore only be characterisic for the specific site

More Related