Detailed PSC formation in a two-dimensional chemical transport model of the stratosphere

A new two-dimensional zonal model of the\udstratosphere, based on a formulation in an isentropic framework, with complete\udchemistry has been coupled with a high resolution detailed microphysical model\udfor polar stratospheric clouds (PSCs). The 2D model chemistry includes all\udpresently known heterogeneous processes on sulfate aerosols and PSCs. The\udcoupling of these two models, with inherently different time scales, is\uddiscussed. It is demonstrated that in order to obtain a realistic\udinterrelationship between NO_y and N₂O an accurate\udsimulation of the sedimentation by PSC particles is necessary. A good agreement\udof model PSC presence and observations is found for the Antarctic polar winter\udwithout the need to impose additional artificial temperature variations in the\udmodel. The calculated occurrence of polar stratospheric clouds and resulting\udheterogeneous chemistry during the Antarctic winter are discussed. Sensitivity\udof the polar stratospheric chemical composition and cloud formation for\uddifferent perturbations is investigated by studying the effects of transport\udacross the polar vortex boundary and heterogeneous processing by an enhanced\udsulfate aerosol load. The importance of including sedimentation for all cases is\udalso discussed