INTRODUCTIONThe particulate matter suspended in the atmosphere is strongly linked to numerous air pollution problems. These include the -direct and indirect- influences on the radiative budget of the atmosphere, the potential for adverse health effects, the influence of particles on the long-range transport of air pollutants and the interaction of particles with clouds. Therefore air quality models have to consider the processes of particle formation, transport and deposition with respect to aerosol chemistry as well as aerosol dynamics. Due to the strong interactions between the gas phase and the aerosol phase, the aerosol model has to be fully coupled to a gas phase model. The Modal Aerosol Dynamics modeling technique as a time and memory efficient method for modeling aerosol distributions provides a suitable approach to realize this purpose even in complex three-dimensional Eulerian models.MODEL DESCRIPTIONThe Modal Aerosol Dynamics Model MADE for Europe has been developed from the Regional Particulate Model (RPM, Binkowski and Shankar, 1995), adapted for European conditions and implemented into the Eulerian chemistry transport model EURAD (EURopean Air pollution Dispersion model, Hass et al., 1995; Ackermann et al., 1995). The size distribution of the submicrometer aerosol is represented by two overlapping intervalls (modes) assuming a lognormal distribution within each mode. Coagulation is treated within each mode as well as between the modes. Aerosol mass can be increased by direct emission of particles, the formation of new particles from the gas phase (nucleation) and by growth due to condensation of water.Given a the kth moment of a distribution defined as the model solves the continuity equation for three moments in each of the two modes, thus accounting for horizontal and vertical transport by advection and diffusion, emissions and aerosol dynamics.THREEDIMENSIONAL SIMULATIONTo investigate the applicability of the new aerosol dynamics model in complex threedimensional chemistry models an episode in July 1994 has been simulated with the coupled system of MADE and EURAD. Figure 1 shows as an example the modeled distribution of the aerosol number concentration between the two modes after two days of simulation over the model domain. Whereas the distribution in the Aitken mode is dominated by the emission patterns, with high concentrations in regions of high emissions and strong horizontal gradients, the accumulation mode shows maximum concentration along the Scandinavian west coast, indicating long-range transport of an aged aerosol plume.RECENT DEVELOPMENTS AND APPLICATIONSIn previous versions aerosol chemistry was restricted to the sulfate-nitrate-ammonia and water system. Since secondary organics comprise a major portion of the atmospheric aerosol we will describe the extension of MADE to organic substances in the aerosol phase. This allows to study the formation of secondary organic particles, their impact on the size distribution of the aerosol population and the response of the gas phase chemistry to the formation of particles on a regional scale over Europe. The simulations will be performed with a prototype version of the aerosol code from the USEPA-Models3 system, thus providing a test case for this new community model platform.