Vortrag, Atmospheric Transport and Chemistry in Forest Ecosystems, Thurnau: 05.10.2009 - 08.10.2009
Abstract:
Tropospheric ozone is known to have negative effect on vegetation, affecting plant tissue, photosynthesis and other physiological functions. To investigate the vertical distribution of ozone depositions at different levels above, within and below spruce forest, ozone eddy covariance fluxes at 4 levels (1, 17, 25 and 32 m) were measured. Meanwhile, some meteorological components (temperature, humidity, wind speed etc.), reactive and non-reactive gases (O3, NO, NO2, CO2 and H2O) concentration profiles at 11 heights were also measured in Fichtelgebirge Mountains, Germany. The raw ozone fluxes at different levels were corrected by a serial of steps, e.g. the errors caused by lag time, insufficient frequency response and instruments separation, instruments tilt, air temperature and humidity fluctuation, etc. Particularly, in the experiments, 3 kinds of fast response ozone sonde were employed. Via side-by-side comparison, large differences in the final results were found. To eliminate systematic error induced by different sondes, one sonde was determined as the ‘relative standard’ by using spectral analysis method. Corrected ozone deposition velocities, mixing ratios and fluxes at different levels were compared and analyzed. The results show that (1) the mean deposition velocities were 0.57 cm s-1 (above canopy, 32 m), 0.41 cm s-1 (within canopy, 17 m) and 0.05 cm s-1 (below canopy, 1 m) in daytime, and the corresponding values were 0.28 cm s-1, 0.19 cm s-1 and 0.04 cm s-1 in night time, respectively. The fluxes at 3 levels above, within and below canopy were –527 ng m-2 s-1, –334 ng m-2 s-1 and –36 ng m-2 s-1 in daytime and -248 ng m-2 s-1, –144 ng m-2 s-1 and –24 ng m-2 s-1 in night time, respectively. Ozone storage changes can also influence ozone fluxes in different layers. The mean storage change rates for entire canopy are 12.1 ng m-2 s-1 in daytime and –17.8 ng m-2 s-1 in night time. Mean daily ozone deposition from upper atmosphere above forest is -35.48 mg m-2 d-1, the mean daily deposition amount in different layers were 2.68 mg m-2 d-1 (0 m to 1 m), 19.34 mg m-2 d-1 (1 m to 17 m) and -13.46 mg m-2 d-1 (17 m to 32 m) and the corresponding ratios to the total deposition were 7.6%, 54.5% and 37.9%.