Quasi‐biennial oscillation and tracer distributions in a coupled chemistry‐climate model

Abstract

We have used a fully coupled chemistry‐climate model (CCM), which generates its own wind and temperature quasi‐biennial oscillation (QBO), to study the effect of coupling on the QBO and to examine the QBO signals in stratospheric trace gases, particularly ozone. Radiative coupling of the interactive chemistry to the underlying general circulation model tends to prolong the QBO period and to increase the QBO amplitude in the equatorial zonal wind in the lower and middle stratosphere. The model ozone QBO agrees well with Stratospheric Aerosol and Gas Experiment II and Total Ozone Mapping Spectrometer satellite observations in terms of vertical and latitudinal structure. The model captures the ozone QBO phase change near 28 km over the equator and the column phase change near ±15° latitude. Diagnosis of the model chemical terms shows that variations in NOx are the main chemical driver of the O3 QBO around 35 km, i.e., above the O3 phase change.