Decadal variability of the tropical stratosphere: Secondary influence of the El Niño-Southern Oscillation

A decadal variation of tropical lower stratospheric ozone and temperature has previously been identified that correlates positively with the 11 year solar activity cycle. However, the El Niño–Southern Oscillation (ENSO) also influences lower stratospheric ozone and temperature. It is therefore legit...

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Bibliographic Details
Published in:Journal of Geophysical Research: Atmospheres 2010-06, Vol.115 (D11), p.n/a
Main Authors: Hood, L. L., Soukharev, B. E., McCormack, J. P.
Format: Article
Language:English
Subjects:
Atmospheric sciences
Climate change
Earth
El Nino
ENSO
Geophysics
Ozone
Solar activity
solar variability
Southern Oscillation
Statistical models
Stratosphere
Upwelling
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Summary:A decadal variation of tropical lower stratospheric ozone and temperature has previously been identified that correlates positively with the 11 year solar activity cycle. However, the El Niño–Southern Oscillation (ENSO) also influences lower stratospheric ozone and temperature. It is therefore legitimate to ask whether quasi‐decadal ENSO variability can contribute to this apparent solar cycle variation, either accidentally because of the short measurement record or physically because solar variability affects ENSO. Here we present multiple regression analyses of available data records to compare differences in results obtained with and without including an ENSO term in the statistical model. In addition, simulations are performed using the NRL NOGAPS‐ALPHA GCM for warm/cold ENSO conditions to test for consistency with the ENSO regression results. We find only very minor changes in annual mean solar regression coefficients when an ENSO term is included. However, the observed tropical ENSO response provides useful insights into the origin of the unexpected vertical structure of the tropical solar cycle ozone response. In particular, the ENSO ozone response is negative in the lower stratosphere due to increased upwelling but changes sign, becoming positive in the middle stratosphere (5–10 hPa) due mainly to advective decreases of temperature and NOx, which photochemically increase ozone. A similar mechanism may explain the observed lower stratospheric solar cycle ozone and temperature response and the absence of a significant response in the tropical middle stratosphere.
ISSN:0148-0227
2169-897X
2156-2202
2169-8996
DOI:10.1029/2009JD012291