HR: 1330h
AN: A32A-0105    [PDF]
TI: Simulation of BVOC Fluxes and Chemical Transformations with a One-dimensional Canopy Chemistry Model for the BEWA Campaigns
AU: Forkel, R
EM: renate.forkel@imk.fzk.de
AF: Institute for Meteorology and Climate Research (IMK-IFU), Forschungszentrum Karlsruhe GmbH, Kreuzeckbahnstrasse 19, Garmisch-Partenk., 82467 Germany
AU: Rappengl\"uck, B
EM: bernhard.rappenglueck@imk.fzk.de
AF: Institute for Meteorology and Climate Research (IMK-IFU), Forschungszentrum Karlsruhe GmbH, Kreuzeckbahnstrasse 19, Garmisch-Partenk., 82467 Germany
AU: * Steinbrecher, R
EM: rainer.steinbrecher@imk.fzk.de
AF: Institute for Meteorology and Climate Research (IMK-IFU), Forschungszentrum Karlsruhe GmbH, Kreuzeckbahnstrasse 19, Garmisch-Partenk., 82467 Germany
AB: Numerical modeling can help to investigate the role of the different pathways for chemical degradation of biogenic volatile organic compunds (BVOC) and the effect of chemical reactions on the net BVOC fluxes from forest canopies. Starting from specified initial conditions the one-dimensional canopy-chemistry model CACHE predicts profiles of temperature, humidity, and chemical species. CACHE includes the energy balance at the leaf surfaces, vertical turbulent transport of heat, water vapor, and gas phase chemical compounds within and above the canopy, emission of biogenic VOC, chemical transformation and deposition of chemical constituents, and heat and moisture transport in the soil. Simulations with CACHE were carried out as part of the joint project BEWA 2000 for the 22 'golden days' during the summer 2001 and 2002 field campaigns at the Waldstein site (Fichtelgebirge, Germany). For the measuring site - a 20 m high spruce forest - the observed diurnal course of temperature and ozone are reproduced well by the model. Nighttime deposition was found to have a major effect on the diurnal course of the ozone concentration. A comparison with the REA measurements during the BEWA campaigns shows that the monoterpene fluxes and concentrations are generally reproduced very well. Furthermore, the fluxes of photooxidants like H$_2$O$_2$ show good agreement between measured and modeled values. The simulations however indicate, that it is necessary to include the emission of aldehydes and acetone in order to reproduce the observed fluxes and concentrations of these species. The model results show that during the daytime the effective fluxes at the canopy top are generally about 10 % lower than the potential fluxes, i.e. the fluxes without considering chemical degradation within the canopy. It was found that even during daytime the NO$_{3}$ radical can contribute significantly to monoterpene degradation in the lower part of the canopy. For example, within the canopy NO$_{3}$ contributes 30 to 50 % to the total degradation of limonene at noontime.
UR: http://imk-ifu.fzk.de/bewa2000
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting