M. J. Schwartz, et al.
Climatology and variability of trace gases in extratropical double-tropopause regions from MLS, HIRDLS, and ACE-FTS measurements
Journal of Geophysical Research: Atmospheres (2014JD021964), 120(2), 843-867, 2015; doi: 10.1002/2014JD021964
O3 18OO2 O18OO O17OO H2O HDO H218O H217O CH4 13CH4 CH3D HNO3 CO 13CO C18O C17O Middle atmosphere Stratosphere/troposphere interactions Middle atmosphere dynamics Remote sensing double tropopause composition UTLS


Upper tropospheric and lower stratospheric measurements from the Aura Microwave Limb Sounder (MLS), the Aura High Resolution Dynamics Limb Sounder (HIRDLS), and the Atmospheric Chemistry Experiment-Fourier transform spectrometer (ACE-FTS) are used to present the first global climatological comparison of extratropical, nonpolar trace gas distributions in double-tropopause (DT) and single-tropopause (ST) regions. Stratospheric tracers, O3, HNO3, and HCl, have lower mixing ratios ∼2–8 km above the primary (lowermost) tropopause in DT than in ST regions in all seasons, with maximum Northern Hemisphere (NH) differences near 50% in winter and 30% in summer. Southern Hemisphere winter differences are somewhat smaller, but summer differences are similar in the two hemispheres. H2O in DT regions of both hemispheres shows strong negative anomalies in November through February and positive anomalies in July through October, reflecting the strong seasonal cycle in H2O near the tropical tropopause. CO and other tropospheric tracers examined have higher DT than ST values 2–7 km above the primary tropopause, with the largest differences in winter. Large DT-ST differences extend to high NH latitudes in fall and winter, with longitudinal maxima in regions associated with enhanced wave activity and subtropical jet variations. Results for O3 and HNO3 agree closely between MLS and HIRDLS, and differences from ACE-FTS are consistent with its sparse and irregular midlatitude sampling. Consistent signatures in climatological trace gas fields provide strong evidence that transport from the tropical upper troposphere into the layer between double tropopauses is an important pathway for stratosphere-troposphere exchange.


  author = "M. J. Schwartz and G. L. Manney and M. I. Hegglin and N. J. Livesey and M. L. Santee and W. H. Daffer",
  title = "Climatology and variability of trace gases in extratropical double-tropopause regions from MLS, HIRDLS, and ACE-FTS measurements",
  year = 2015,
  journal = "Journal of Geophysical Research: Atmospheres",
  volume = 120,
  number = 2,
  pages = "843-867",
  month = "Jan",
  keywords = "O3, 18OO2, O18OO, O17OO, H2O, HDO, H218O, H217O, CH4, 13CH4, CH3D, HNO3, CO, 13CO, C18O, C17O, Middle atmosphere, Stratosphere/troposphere interactions, Middle atmosphere dynamics, Remote sensing, double tropopause, composition, UTLS",
  doi = "10.1002/2014JD021964",
  url = "",
  note = "2014JD021964"
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