The Key Role of Coupled Chemistry-Climate Interactions in Tropical Stratospheric Temperature Variability

The purpose of this study is to quantify the effects of coupled chemistry-climate interactions on the amplitude and structure of stratospheric temperature variability. To do so, the authors examine two simulations run on version 4 of the Whole Atmosphere Coupled Climate Model (WACCM): a free-running'' simulation that includes fully coupled chemistry-climate interactions and a specified chemistry'' version of the model forced with prescribed climatological-mean chemical composition. The results indicate that the inclusion of coupled chemistry-climate interactions increases the internal variability of temperature by a factor of;2 in the lower tropical stratosphere and-to a lesser extent-in the Southern Hemisphere polar stratosphere. The increased temperature variability in the lower tropical stratosphere is associated with dynamically driven ozone-temperature feedbacks that are only included in the coupled chemistry simulation. The results highlight the fundamental role of two-way feedbacks between the atmospheric circulation and chemistry in driving climate variability in the lower stratosphere.