On the influence of stratospheric water vapor changes on the tropospheric circulation

Joshi, M. M., Charlton, A. J. ORCID: https://orcid.org/0000-0001-8179-6220 and Scaife, A. A. (2006) On the influence of stratospheric water vapor changes on the tropospheric circulation. Geophysical Research Letters, 33 (9). L09806. ISSN 0094-8276 doi: 10.1029/2006GL025983

Abstract/Summary

Observations suggest that the mixing ratio of water vapour in the stratosphere has increased by 20–50% between the 1960s and mid-1990s. Here we show that inclusion of such a stratospheric water vapour (SWV) increase in a state-of-the-art climate model modifies the circulation of the extratropical troposphere: the modeled increase in the North Atlantic Oscillation (NAO) index is 40% of the observed increase in NAO index between 1965 and 1995, suggesting that if the SWV trend is real, it explains a significant fraction of the observed NAO trend. Our results imply that SWV changes provide a novel mechanism for communicating the effects of large tropical volcanic eruptions and ENSO events to the extratropical troposphere over timescales of a few years, which provides a mechanism for interannual climate predictability. Finally, we discuss our results in the context of regional climate change associated with changes in methane emissions.