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The SPARC-Reanalysis Intercomparison Project (S-RIP)
Chapter 6: Stratosphere-Troposphere Coupling

Our goal is to assess stratosphere-troposphere coupling in the 9 currently available atmospheric reanalysis datasets providing both a review of the literature and a detailed comparison of all the reanalyses together in one place. In particular, this chapter will address these questions:

  • Which measures of stratosphere-troposphere coupling are well captured by the reanalyses?
  • Which measures of stratosphere-troposphere coupling are uncertain and/or differ significantly among the reanalyses?
  • Can we objectively determine that particular reanalyses and/or time periods (e.g. the pre-satellite era) poorly reflect the real atmosphere?

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Chapter structure
A working draft of the chapter

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Lead Authors:
Edwin Gerber (New York University, USA)
Patrick Martineau (McGill University, Canada)

Contributing authors (tentative):
Mark P. Baldwin (University of Exeter, UK)
David Barriopedro (Universidad Complutense de Madrid, Spain)
Thomas Birner (Colorado State University, USA)
Thomas J. Bracegirdle (British Antarctic Survey, UK)
Amy Butler (NOAA ESRL, USA)
Natalia Calvo (Universidad Complutense de Madrid, Spain)
Lesley Gray (University of Oxford)
Steven Hardiman (Met Office, UK)
Peter Hitchcock (University of Cambridge, UK)
Maddalen Iza (Universidad Complutense de Madrid, Spain)
Alexey Karpechko (Finnish Meteorological Institute, Finland)
Kirstin Krueger (GEOMAR, Germany)
Hua Lu (British Antarctic Survey, UK)
Patrick Martineau (McGill University, Canada)
Daniel Mitchell (University of Oxford, UK)
Andrew Orr (British Antarctic Survey, UK)
Cristina Pena-Ortiz (University of Seville, Spain)
Thomas Reichler (University of Utah, USA)
Seok-Woo Son (Seoul National University, Korea)
Masakazu Taguchi (Aichi University of Education, Japan)

Chapter Structure

Currently, the chapter is being organized around different time scales, although this structure may evolve.

  • Coupling on Synoptic to Intraseasonal Time Scales, e.g. SSWs, blocking, annular modes, planetary wave coupling, wave-mean flow interactions
  • Coupling on Intraseasonal to Interannual Time Scales, e.g. Volcanoes, ENSO, QBO (coordinated w/ the S-RIP QBO chapter), and Solar Cycle
  • Coupling on Interdecadal Time Scales and Longer, e.g. coupling to meridional overturning circulation of the ocean, and the impact of stratospheric ozone loss and other forcings on tropospheric trends
For direct comparison of the reanalyses, we will focus on the satellite era, 1979-2012, where almost all reanalyses are available. (ERA-40 is an exception, ending in 2002.) For some measures of stratosphere-troposphere coupling, however, uncertainty due to limited sampling in time (e.g. the finite number of Sudden Warmings), may dwarf uncertainty due to differences in the reanalysis procedures. For this reason, we will also consider the reanalyses records stretching back to 1957/8, where, at least in the Northern Hemisphere, there may still be enough ground based observations to constrain the reanalysis.

We hope to cover measures of stratosphere-troposphere coupling over the entire globe, although much of the literature has focussed on coupling in the midlatitudes, even when considering effects stemming from the tropics, e.g. the Holton-Tan effect. Recent work has suggested that the stratosphere can act as a bridge connecting tropical dynamics (ENSO) to the high latitudes.