Jocher, G; Eigenmann, R*; Serafimovich, A; Foken, T: Free convection events on a spruce forest clearing
Poster, Atmospheric Transport and Chemistry in Forest Ecosystems, Thurnau: 05.10.2009 - 08.10.2009

Experimental data of a modified Bowen ratio mast installed during the EGER (ExchanGE processes in mountainous Regions) project on a clearing in a spruce forest (Picea abies) at the Waldstein site in the Fichtelgebirge Mountains are used to investigate the initiation and occurrences of free convection events. Free convection events are found to be triggered on the heated ground of the clearing if buoyant forces dominate over shear forces within turbulence production. These situations are detected by the stability parameter (ratio of the measurement height to the Obukhov length) calculated from turbulent flux data of the modified Bowen ratio system. Single free convection events are selected and compared to measurement data of a nearby installed turbulence tower above the spruce forest and a Sodar measurement system. The latter is situated on the clearing and provides wind velocity information of the boundary layer and thus of the local circulation system, which possibly influences the initiation of the observed free convection events.

Letzte Änderung 02.11.2009