Role of nitrogen oxides in the stratosphere: A reevaluation based on laboratory studies

The changes in chemical partitioning and stratospheric O-3 abundance due to the recently measured rate coefficients for the O + NO2, OH + HNO3, and OH + NO2 reactions are examined using a two-dimensional model. The rate constant changes increase NOx abundance (up to 40%) and NOx-catalyzed O-3 destruction, and extend down by several kilometers the altitude region where NOx dominates catalytic O-3 destruction. Reductions in the abundance of HOx (10-30%) and ClOx (20-40%) in the lower stratosphere partially buffer the effect on column O-3 amount. Column O-3 at middle and high latitudes is reduced by 2-10% depending on season for current halogen levels. The model derived long-term O-3 trend at midlatitudes due to increases in anthropogenic halogens is reduced by approximately 30%.