Stratospheric ozone in the post-CFC era

F Li,R S Stolarski,P A Newman

doi:10.5194/acp-9-2207-2009

Abstract

Abstract. Vertical and latitudinal changes in the stratospheric ozone in the post-chlorofluorocarbon (CFC) era are investigated using simulations of the recent past and the 21st century with a coupled chemistry-climate model. Model results reveal that, in the 2060s when the stratospheric halogen loading is projected to return to its 1980 values, the extratropical column ozone is significantly higher than that in 1975–1984, but the tropical column ozone does not recover to 1980 values. Upper and lower stratospheric ozone changes in the post-CFC era have very different patterns. Above 15 hPa ozone increases almost latitudinally uniformly by 6 Dobson Unit (DU), whereas below 15 hPa ozone decreases in the tropics by 8 DU and increases in the extratropics by up to 16 DU. The upper stratospheric ozone increase is a photochemical response to greenhouse gas induced strong cooling, and the lower stratospheric ozone changes are consistent with enhanced mean advective transport due to a stronger Brewer-Dobson circulation. The model results suggest that the strengthening of the Brewer-Dobson circulation plays a crucial role in ozone recovery and ozone distributions in the post-CFC era.

Highlights

The stratospheric ozone layer is expected to recover to pre1980 levels in the middle of the 21st century with the projected decline of the stratospheric halogen loading (WMO, 2007)
Coupled chemistry-climate model (CCM) simulations have found that the recovery of the stratospheric ozone and halogen to 1980 levels will not happen at the same time, because ozone recovery is strongly dependent on temperature and transport, which in the middle 21st century, are Correspondence to: F
This paper investigates the impacts of climate change on ozone recovery using simulations of the recent past and future (21st century) from the Goddard Earth Observing System (GEOS) CCM (Pawson et al, 2008)

Summary

Introduction

An important aspect of ozone recovery is the vertical and latitudinal characteristics of ozone distributions in the post-chlorofluorocarbon (CFC) era, which has not been extensively investigated by previous work. Decadal differences in the stratospheric ozone between 2060s and 1975– 1984 are examined when the halogen amounts are nearly the same during these two decades. These differences are interpreted as mainly caused by climate change and are consistent with an increased Brewer-Dobson circulation in the lower stratosphere and strong cooling in the upper stratosphere

Model simulations

Model results

Findings

Discussion and conclusions