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| Klemm, O; Held, A; Forkel, R; Gasche, R; Kanter, H-J; Rappenglück, B; Steinbrecher, R; Müller, K; Plewka, A; Cojocariu, C; Kreuzwieser, J; Valverde-Canossa, J; Schuster, G; Moortgat, GK; Graus, M; Hansel, A: Experiments on forest/atmosphere exchange: Climatology and Fluxes during two summer campaigns in NE Bavaria, Atmospheric Environment, 40, Supplement 1,3-20 (2006), doi:10.1016/j.atmosenv.2006.01.060 | |
Abstract:
During two summer field campaigns in 2001 and 2002, biosphere/atmosphere exchange fluxes of energy, gases, and
particles were quantified in a Norway spruce forest in NE Bavaria at 775m a.s.l. The overall goal of the BEWA campaigns
was to study the influence of the emissions of reactive biogenic volatile organic compounds (BVOCs) on chemical and
physical processes in the atmosphere, and an overview over the meteorological conditions, experimental frame, and the
achieved results is provided. A rigorous quality assurance/quality control plan was implemented. From analysis of
meteorological conditions and experimental success, golden day periods were selected for coordinated data analysis. These
periods cover typical summertime conditions with various wind directions, NOx mixing ratios between 2 and 10 ppb, and
O3 mixing ratios ranging between 13 and 98 ppb. Diurnal patterns of trace gas concentrations resulted from the dynamics
of the boundary layer, from regional atmospheric processes (for example production of O3 in the atmosphere), and
deposition. Turbulence also exhibited a diurnal pattern indicating thermal production during daytime and calm conditions
during nighttime. However, in many cases, turbulence was often well developed during the nights. Horizontal advection of
air masses into the trunk space occurred due to the patchiness of the forest. Nevertheless, for most conditions, the
application of a one-dimensional model to describe the vertical exchange processes was appropriate. Therefore, the use of
one single meteorological tower to study biosphere/atmosphere exchange is valid. Measured turbulent vertical exchange
fluxes were estimated to be representative within an error of less than 25%. The results for VOC concentrations and fluxes were rather heterogeneous. Both model and measurements demonstrated that the Norway spruce trees acted as a weak source of formaldehyde. |
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