1Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
2College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China
3Chemical Science Division, Earth System Research Laboratory, NOAA, Boulder, CO, USA
Received: 14 Aug 2009 – Discussion started: 16 Oct 2009
Abstract. This study examines the seasonality of tropical lower-stratospheric temperature trends using the Microwave Sounding Unit lower-stratospheric channel (T4) for 1980–2008. We present evidence that this seasonality is largely a response to changes in the Brewer-Dobson circulation (BDC) driven by extratropical wave forcing. We show how the tropical T4 trend can be used as an indicator of changes in the BDC, and find that the BDC is strengthening for 1980–2008 in June–November related to the Southern Hemisphere (SH) and in December–February to the Northern Hemisphere (NH). In marked contrast, we find that the BDC is weakening in March–May, apparently because of a weakening of its northern cell. The novel observational evidence on the seasonal dependence of the BDC trends presented in this study has important implications for the understanding of climate change in the stratosphere as well as testing climate model simulations.
Revised: 10 Mar 2010 – Accepted: 11 Mar 2010 – Published: 18 Mar 2010
Fu, Q., Solomon, S., and Lin, P.: On the seasonal dependence of tropical lower-stratospheric temperature trends, Atmos. Chem. Phys., 10, 2643-2653, doi:10.5194/acp-10-2643-2010, 2010.