Characteristics of horizontal and vertical fluxes of CO2 during the ADVEX Experiment at the Wetzstein site, in Thuringia, Germany

Marcelo Zeri1, Corinna Rebmann1, W. Kutsch1, C. Feigenwinter2, ADVEX teams

(1) Max Planck Institute for Biogeochemistry; (2) University of Basel, Institute of Meteorology, Climatology and Remote Sensing, Basel, Switzerland

Overview

Introduction Site characteristics Advection versus micrometeorology Indirect measures of advection periods Conclusions

The Advection Experiment

Performed in three European sites (Renon, Italy; Wetzstein, Germany; Norunda, Sweden)

Measurements performed with multiple towers

Horizontal and vertical advection of CO2 calculated to a volume

First results summarized in Feigenwinter et al. (Agr. For. Met, accepted)

The Wetzstein site

The Wetzstein site

Spruce ecosystem Located at 785 m a.s.l. Average temperature of

~ 6 C; annual precipitation of 990 mm

Unexplained high nighttime fluxes of CO2

One of the sites of the CarboEurope-IP Advection Experiment

Advection versus micrometeorology Inspection of the time series of horizontal

and vertical advection (HA and VA) Relation with variables as wind speed

and direction, stratification, and CO2-flux Three patterns identified:

No advection Both terms important (|HA|>|VA|) HA only

First case, May 2006

Advective fluxes provided by Christian Feigenwinter

Second case, May-June, 2006

Advective fluxes provided by Christian Feigenwinter

Identifying periods with advection

Conclusions The evolution of the advection terms exemplify the non-

stationary nature of these terms. Site specific characteristics of the topography, and local synoptic conditions may influence their evolution in time.

As the advection terms are intermittent, an average for a continuous period may not represent its real day-to-day contribution.

Periods with horizontal advection can be identified by, for example, the maximum in the vertical profile of wind speed below the canopy or by the positive correlation w’u’ at the trunk space.

Periods characterized by advection should be removed from the determination of annual sums of CO2-flux, as commonly done with nights with low friction velocity.

Acknowledgements

The authors gratefully acknowledge the collection of data by the field crew from the Max Planck Institute for Biogeochemistry and from the ADVEX Experiment in 2006.

Reference Feigenwinter, C. et al., The ADVEX advection

field campaigns: Comparison of mean horizontal and vertical non turbulent advective fluxes at three CarboEurope forest sites. Agricultural and Forest Meteorology, (accepted).