8.6 Relative Importance of Mechanisms Governing Interannual Stratosphere to Troposphere Ozone Transport

Wednesday, 28 June 2017: 11:45 AM
Salon G-I (Marriott Portland Downtown Waterfront)
John R. Albers, University of Colorado, Boulder, CO; and J. Perlwitz, G. N. Kiladis, Z. D. Lawrence, A. H. Butler, T. Birner, G. L. Manney, A. O. Langford, and J. Dias

Factors governing the strength and frequency of stratospheric ozone intrusions over the Pacific-North American region are considered for their role in modulating tropospheric ozone on interannual timescales. The strength of the association between two major modes of climate variability -- ENSO and the Northern annular mode (NAM) -- and the amount of ozone contained in stratospheric intrusions is tested in the context of two mechanisms that modulate stratosphere-to-troposphere transport (STT) of ozone: (StratVarO3) the winter season buildup of ozone abundances in the lowermost stratosphere (LMS), and (JetVar) North Pacific jet and wave breaking variability during late spring. In essence, StratVarO3 corresponds to variability in the amount of ozone per intrusion, while JetVar corresponds to the frequency of intrusions.

The resulting analysis suggests that StratVarOis more important than JetVar for driving interannual variations in STT of ozone over the Pacific-North American region. In particular, the abundance of ozone in the LMS at the end of winter is shown to be a robust indicator of the amount of ozone that will be contained in stratospheric intrusions during the ensuing spring and summer. Additionally, it is shown that the winter season time-summed strength of the stratospheric NAM is a useful predictor of ozone intrusion strength. The results also suggest a nuanced relationship between the phase of ENSO and STT of ozone. It is found that while ENSO-related jet variability is associated with STT variability, it is wave breaking frequency rather than typical ENSO teleconnection patterns that are responsible for the ENSO-STT relationship.

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