Investigation Description: Our contribution to the SOLVE campaign will be focused primarily on analysis of the ER-2 wake under cold ambient conditions. The AER far-wake model [Danilin et al., 1997] will be the main tool for this analysis. This model calculates concentrations of principal oxygen, hydrogen, nitrogen, chlorine, bromine, and sulfur species in the stratosphere and includes more than 100 gas-phase, photolytic, and heterogeneous reactions on sulfate aerosol and polar stratospheric particles (PSCs). Rates of these reactions are adopted according to the JPL-97 recommendations [DeMore et al., 1997], with several updates for the nitrogen species reactions and O(1D) quantum yield of the ozone photolysis. The sulfur photochemistry and microphysics are the same as in the AER 2-D model [Weisenstein et al., 1997]. Briefly, the aerosol module includes 40 bins from 0.39 nm to 3.2 microns with volume-doubling binning. This module calculates nucleation, coagulation, and evaporation/condensation of binary H₂SO₄/H₂O particles. Possible effects of chemi-ions (which are not calculated in our model) could be accounted for by a proper initialization of our model according to Yu and Turco [1998]. Additionally, our model calculates PSC formation and evolution using either NAT (HNO3*3H2O) or supercooled ternary solution (STS) PSC schemes [Danilin et al., 1998]. During the SOLVE campaign, we will initialize our model from available ER-2 measurements and from an AER 2-D model calculation for the species not sampled by the ER-2.