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MOCAGE is a three-dimensional grid-point chemical-transport model with 3 domains and different horizontal resolutions (Figure 3). The model includes 47 vertical layers from the surface up to 5 hPa (Figure 4), meaning 1 million grid-points. MOCAGE is forced by ARPEGE analyses and uses a semi-Lagrangian transport scheme. Two convection schemes are available in the model [Tiedtke, Mon. Wea. Rev., 1989 ; Betchold et al., QJR Meteorol. Soc., 2000] and surface emissions for chemical species are from IGAC/GEIA and RIVM/EDGAR scaled by IPCC recommendations. This model can use several schemes to describe either stratospheric chemistry (REPROBUS, Lefèvre et al., J. Geophys. Res., 1994), or tropospheric chemistry (RACM, Stockwell et al., J. Geophys. Res., 1997 ; SAPRC99, California Air Resources Board ; Harvard-GISS, Wang et al., J. Geophys. Res., 1998 ; EMEP, Simpson et al., EMEP MSC-W note 2193, 1993 ; MELCHIOR, Beckmann et al ;, Atm. Env., 2000), or both tropospheric-stratospheric chemistry (meaning for instance, 115 chemical species and 380 chemical reactions for the RACM + REPROBUS scheme). Hence, MOCAGE is a flexible tool with a one-dimensional version for sensitivity studies and is also computationally efficient (1 day of simulation for 1 CPU hour of FUJITSU VPP-5000 for the full 3D version).
Future developments of the model will include a high-resolution regional domain (0.1° x 0.1°) for air quality studies and predictions, data assimilation and coupling MOCAGE to the ARPEGE GCM for source gases (N2O, CH4, CFCs) and ozone as it was already done for ozone the REPROBUS CTM as explained in parts 2, 3 and 4.
Figure 3 : Geographical domains taken into account in MOCAGE with associated horizontal resolution
Figure 4 : Vertical distribution (left column) in MOCAGE (47 sigma-pressure
levels in the standard version). Intermediate layers are defined
asP(i) = A(i) + B(i) x Psurfacewhere functions Aand Bare shown in the right column