International ISSI Team: Quantifying Hemispheric Differences in Particle Forcing Effects on Stratospheric Ozone

International ISSI Team:

Quantifying Hemispheric Differences in Particle Forcing Effects on Stratospheric Ozone

Significant progress has been made in the understanding of energetic particle precipitation (EPP) and its effects on the middle and upper atmosphere. Model simulations now include the chemical and energetic forcing from a broad range of energetic particles. Comparisons of simulation results with observations have shown that the production of odd-nitrogen species and the subsequent catalytic loss of ozone are well simulated. It is becoming clear that the dynamics of the winter polar stratosphere in the Northern Hemisphere play a vital role in transport of NOx and ozone loss. Major stratospheric sudden warmings, which have a frequency of approximately 0.6/y, appear to either enhance or reduce NOx downward transport. In contrast, the lack of variability of the winds in the Southern Hemisphere winter results in a consistent conduit of upper atmospheric NOx into the stratosphere.

Introduction

This Team will use a combination of satellite data (e.g., from ENVISAT) and model simulations to quantify hemispheric differences in wintertime EPP NOx and its effects on stratospheric ozone. We aim to assess which hemisphere responds more directly to EPP forcing on timescales up to the 11-year solar cycle, and how that varies with meteorology. This is a necessary first step in understanding the role of stratospheric EPP-induced ozone loss in driving tropospheric climate variability.