Talk, Atmospheric Transport and Chemistry in Forest Ecosystems, Thurnau: 2009-10-05 - 2009-10-08
In the frame of the EGER project the contribution of coherent structures to the transfer of energy and matter in a tall spruce canopy was investigated. Two measuring campaigns were carried out at the Waldstein site in the Fichtelgebirge mountains. Observations of coherent structures were obtained by a vertical profile of sonic anemometers equipped with fast gas analyzers. Duration of coherent events detected in the trunk space of the forest was two times longer than duration of coherent events in the canopy. The analysis shows dominant momentum and sensible heat transport by coherent structures in the canopy space. Carbon dioxide and latent heat transport by coherent structures increases with height within the canopy and reaches a maximum at the upper canopy level. The flux contribution of the ejection phase decreases with increasing height within the canopy and becomes dominant above the canopy level. The flux fraction transported during the downward directed sweep phase increases with height within the canopy and becomes the dominating exchange process at the upper canopy level. Close to the ground surface in the subcanopy space, ejection and sweep phase contribute equally to the flux transport. The determined exchange regimes indicate consistent decoupling between trunk space, canopy, air above the canopy during evening, night and morning hours. Entire coupling between all canopy levels and trunk space of the forest was observed around noon.