Application and inter-comparison of atmospheric chemistry mechanisms and advection schemes within the online-coupled regional meteorology chemistry model MCCM

Renate Forkel, Edwin Haas, and Peter Suppan

Institute for Meteorology and Climate Research

Atmospheric Environmental Research (IMK-IFU)

Forschungszentrum Karlsruhe GmbH

Garmisch-Partenkirchen, Germany

Since the huge number of chemical species and reactions involved in the degradation of organic compounds does not permit an explicit treatment of these reactions, the use of condensed mechanisms in regional models is necessary. Such mechanisms are for example the RADM2 (Stockwell et al., 1990) or the RACM (Stockwell et al., 1997) mechanism, which are widely applied in regional air chemistry models. With increased knowledge about biogenic VOC's chemistry, updates of the description of organic chemistry may be necessary. Geiger et al. (2003) introduced a new mechanism based on RACM with improved isoprene and biogenic VOC chemistry.

To understand the behavior of the three mechanisms for the application within regional air chemistry models, two case studies were performed for the three mechanisms: A box-model-inter-comparison and a cross-validation of the simulations with the three-dimensional online-coupled regional air chemistry model MCCM (Grell et al. 2000).

The steady increase in computational power opened the possibilities to performe high resolution air quality simulations along with development of detailed emission inventories. The resulting chemical trace species concentrations demand superior numerical schemes to conserve these local gradients on different scales. Numerical advection schemes for the trace species transport have been developed and implemented into MCCM on the basis of the flux limiting advection schemes of Bott (1989, 1992) in order to account for the conservation of steep gradients, monotony and positive definiteness and their impact to high resolution air quality simulations have been studied.

Bott, A.: A positive definite advection scheme obtained by nonlinear renormalization of the advective fluxes. Mon. Wea. Rev., 117, 1006-1015, 1989.

Bott, A.: Monotone flux limitation in the area-preserving flux-form advection algorithm. Mon. Wea. Rev., 120, 2592-2602, 1992.

Geiger H., Barnes, I., Benjan, I, Benter, T., and Splitter M.: The tropospheric degradation of isoprene: an updated module for the regional chemistry mechanism. Atmos. Environ. 37, 1503-1519, 2003.

Grell, G.A., Emeis, S., Stockwell, W.R., Schoenemeyer, T., Forkel, R., Michalakes, J., Knoche, R., and Seidl, W.: Application of a multiscale, coupled MM5/Chemistry Model to the complex terrain of the VOTALP Valley Campaign, Atmos. Environ., 34, 1435-1453, 2000.

Stockwell, W., Middelton, P., and Chang, J.: The Second Generation Regional Acid Deposition Model – chemical Mechanism for Regional Air Quality Modeling. Journal of Geophysical Research, 95, 16343-18367, 1990.

Stockwell, W., Kirchner, F, Kuhn, M., and Seefeld, S.: A new mechanism for region atmospheric chemistry modeling. Journal of Geophysical Research, 102, 847-879, 1997.