Recent analyses have revealed simple relationships between the simultaneously measured mixing ratios of certain stratospheric constituents. In some cases, the relationship appears to be nearly linear, so that measured concentrations of one can be used to predict the other. We argue here that such relationships are to be expected for species of sufficiently long lifetime. Species whose local lifetimes are longer than quasihorizontal transport time scales are in climatological slope equilibrium, i.e., they share surfaces of constant mixing ratio, and a scatter plot of the mixing ratio of one versus that of the other collapses to a compact curve whose slope at any point is the ratio of the net global fluxes of the two species through the corresponding surface of constant mixing ratio. Species whose local lifetimes are greater than vertical transport time scales are in gradient equilibrium and their mixing ratios display a linear relationship. For species whose atmospheric lifetimes are determined by removal in the stratosphere, the slope of this relationship in the lower stratosphere can be related to the ratio of their atmospheric lifetimes. These statements are illustrated using results from a two-dimensional chemistrytransport model. IntroductionInterpretation of the observed distributions of atmospheric constituent concentrations is often confused by the complexity of transport processes. Concentrations at a fixed location, for example, may fluctuate rapidly in response to horizontal and vertical displacements of air during the passage of meteorological disturbances. Recent work has shown that much simplification can be achieved by using almost-conserved quantities to replace Eulerian coordinates. Thus Schoeberl et al. [1989] and Lair et al. 1990] were able to collate observations taken in different ocations and at different times during the recent airborne stratospheric polar missions by binning the data with respect to potential temperature and potential vorticity [see also Schoeberl and Hartmann, 1991; Schoeberl et al., 1992]. Resulting reconstructions maintained, for example, the sharp tracer gradients near the edge of the polar vortex; these gradients would have been greatly smoothed out by conventional averaging, Paper number 92JD00450 0148-0227 / 92 / 92JD-00450 $ 05.00 given the large latitudinal and temporal fluctuations in the location of this edge. The effectiveness of this technique appears to rest on the fact that potential temperature and potential vorticity may be assumed conserved for long enough to act as Lagrangian tracers during the short-term fluctuations associated with Rossby waves on the edge of the polar vortex. Then, the short-term fluctuations of the mixing ratio isopleths of long-lived tracers are almost coincident with those of potential vorticity and potential temperature. Another useful viewpoint can be obtained by using as reference a very well conserved quantity such as the mixing ratio of N20; the surfaces of constant N20 mixing ratio follow the air motions more precisely than, s...

[1] Measurements of BrO suggest that inorganic bromine (Br y ) at and above the tropopause is 4 to 8 ppt greater than assumed in models used in past ozone trend assessment studies. This additional bromine is likely carried to the stratosphere by short-lived biogenic compounds and their decomposition products, including tropospheric BrO. Including this additional bromine in an ozone trend simulation increases the computed ozone depletion over the past $25 years, leading to better agreement between measured and modeled ozone trends. This additional Br y (assumed constant over time) causes more ozone depletion because associated BrO provides a reaction partner for ClO, which increases due to anthropogenic sources. Enhanced Br y causes photochemical loss of ozone below $14 km to change from being controlled by HO x catalytic cycles (primarily HO 2 +O 3 ) to a situation where loss by the BrO+HO 2 cycle is also important. Citation: Salawitch, R. J.,

[1] The large solar storms in October-November 2003 caused solar proton events (SPEs) at the Earth and impacted the middle atmospheric polar cap regions. Although occurring near the end of the maximum of solar cycle 23, the fourth largest period of SPEs measured in the past 40 years happened 28-31 October 2003. The highly energetic protons associated with the SPEs produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which led to the production of odd hydrogen (HO x ) and odd nitrogen (NO y ). NO x (NO + NO 2 ) was observed by the UARS HALOE instrument to increase over 20 ppbv throughout the Southern Hemisphere polar lower mesosphere. The NOAA 16 SBUV/2 instrument measured a short-term ozone depletion of 40% in the Southern Hemisphere polar lower mesosphere, probably a result of the HO x increases. SBUV/2 observations showed ozone depletions of 5-8% in the southern polar upper stratosphere lasting days beyond the events, most likely a result of the NO y enhancements. Longer-term Northern Hemisphere polar total ozone decreases of >0.5% were predicted to last for over 8 months past the events with the Goddard Space Flight Center two-dimensional model. Although the production of NO y constituents is the same in both hemispheres, the NO y constituents have a much larger impact in the northern than the southern polar latitudes because of the seasonal differences between the two hemispheres. These observations and model computations illustrate the substantial impact of solar protons on the polar neutral middle atmosphere.

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Abstract. A two-dimensional model of sulfate aerosols has been developed. The model includes the sulfate precursor species H2S, CS2, DMS, OCS, and S02. Microphysical processes simulated are homogeneous nucleation, condensation and evaporation, coagulation, and sedimentation. Tropospheric aerosols are removed by washout processes and by surface deposition. We assume that all aerosols are strictly binary water-sulfuric acid solutions without solid cores. The main source of condensation nuclei for the stratosphere is new particle formation by homogeneous nucleation in the upper tropical troposphere. A signficant finding is that the stratospheric aerosol mass may be strongly influenced by deep convection in the troposphere. This process, which could transport gas-phase sulfate precursors into the upper troposphere and lead to elevated levels of S02 there, could potentially double the stratospheric aerosol mass relative to that due to OCS photooxidation alone. Our model is successful at reproducing the magnitude of stratospheric aerosol loading following the Mount Pinatubo eruption, but the calculated rate of decay of aerosols from the stratosphere is faster than that derived from observations.