On the influence of stratospheric water vapor changes on the tropospheric circulation
Joshi, M. M., Charlton, A. J. 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
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To link to this article DOI: 10.1029/2006GL025983
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.