Preprints
https://doi.org/10.5194/acp-2020-1288
https://doi.org/10.5194/acp-2020-1288

  23 Dec 2020

23 Dec 2020

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Is our dynamical understanding of the circulation changes associated with the Antarctic ozone hole sensitive to the choice of reanalysis dataset?

Andrew Orr1, Hua Lu1, Patrick Martineau2, Ed P. Gerber3, Gareth Marshall1, and Tom J. Bracegirdle1 Andrew Orr et al.
  • 1Atmosphere, Ice and Climate, British Antarctic Survey, Cambridge, United Kingdom
  • 2Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
  • 3Courant Institute of Mathematical Sciences, New York University, New York, NY, United States

Abstract. This study quantifies differences among four widely used atmospheric reanalysis datasets (ERA5, JRA-55, MERRA-2, and CSFR) in their representation of the dynamical changes induced by severe springtime polar stratospheric ozone depletion in the Southern Hemisphere during 1980–2001. The intercomparison is undertaken as part of the SPARC (Stratosphere–troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). The dynamical changes associated with the ozone hole are examined by investigating the eddy heat and momentum fluxes and wave forcing. The reanalyses are generally in good agreement in their representation of the expected strengthening of the lower stratospheric polar vortex during the austral spring-summer season, as well as the descent of anomalously strong winds to the surface during summer and the subsequent poleward displacement and intensification of the polar front jet. Differences in the trends in zonal wind are generally small compared to the mean trends. The exception is CSFR, which shows greater disagreement compared to the other three reanalysis datasets, with stronger westerly winds in the lower stratosphere in spring and a larger poleward displacement of the tropospheric westerly jet in summer. Although our results suggest a high degree of consistency across the four reanalysis datasets in the representation of the dynamical changes associated with the ozone hole, there are larger differences in the wave forcing and eddy propagation changes compared to the similarities in the circulation trends. There is a large amount of disagreement in CFSR wave forcing/propagation trends compared to the other three reanalyses, while the best agreement is found between ERA5 and JRA-55. The underlying causes of these differences are consistent with the wind response being more constrained by the assimilation of observations compared to the wave forcing, which is more dependent on the model-based forecasts that can differ between reanalyses. Looking forward, these findings give us confidence that reanalysis datasets can be used to assess changes associated with the ongoing recovery of stratospheric ozone.

Andrew Orr et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Andrew Orr et al.

Andrew Orr et al.

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Short summary
Reanalysis datasets combine observations and weather forecast simulations to create our best estimate of the state of the atmosphere, and are important for climate monitoring. Differences in the technical details of these products means that they may give different results. This study therefore examined how changes associated with the so-called Antarctic ozone hole are represented, which is one of the most important climate changes in recent decades, and showed that they were broadly consistent.
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