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Discussion papers
https://doi.org/10.5194/acp-2019-39
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2019-39
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 25 Jan 2019

Research article | 25 Jan 2019

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.

Multi-timescale variations of modelled stratospheric water vapor derived from three modern reanalysis products

Mengchu Tao1, Paul Konopka1, Felix Ploeger1,2, Xiaolu Yan1, Jonathon S. Wright3, Mohamadou Diallo1, Stephan Fueglistaler4, and Martin Riese1 Mengchu Tao et al.
  • 1Forschungszentrum Jülich (IEK-7: Stratosphere), Jülich, Germany
  • 2Department of Physics, University of Wuppertal, Wuppertal, Germany
  • 3Department of Earth System Science, Tsinghua University, Beijing, China
  • 4Princeton University, Princeton, USA

Abstract. Stratospheric water vapor (SWV) plays important roles in the radiation budget and ozone chemistry and is a valuable tracer for understanding stratospheric transport. Meteorological reanalyses provide variables necessary for simulating this transport; however, even recent reanalyses are subject to substantial uncertainties, especially in the stratosphere. It is therefore necessary to evaluate the consistency among SWV distributions simulated using different input reanalysis products. In this study, we evaluate the representation of SWV and its variations on multiple timescales using simulations over the period 1980–2013. Our simulations are based on the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by horizontal winds and diabatic heating rates from three recent reanalyses: ERA-Interim, JRA-55 and MERRA-2. We present an inter-comparison among these model results and observationally-based estimates, using a multiple linear regression method to study the annual cycle (AC), the quasi-biennial oscillation (QBO), and longer-term variability in monthly zonal-mean H2O mixing ratios forced by variations in the El-Nino–Southern Oscillation and the volcanic aerosol burden. We find reasonable consistency among simulations of the distribution and variability of SWV with respect to the AC and QBO. However, the amplitudes of both signals are systematically weaker in the lower and middle stratosphere when CLaMS is driven by MERRA-2 than when it is driven by ERA-Interim or JRA-55. This difference is primarily attributable to relatively slow tropical upwelling in the lower stratosphere in simulations based on MERRA-2. Two possible contributors of the slow tropical upwelling in the lower stratosphere are found to be the large long-wave radiative effect and the unique assimilation process in MERRA-2. The impacts of ENSO and volcanic aerosol on H2O entry variability are qualitatively consistent among the three simulations despite differences of 50–100 % in the magnitudes. Trends show larger discrepancies among the three simulations. CLaMS driven by ERA-Interim produces a neutral to slightly positive trend in H2O entry values over 1980–2013 (+0.01 ppmv decade-1), while both CLaMS driven by JRA-55 and CLaMS driven by MERRA-2 produce negative trends but with significantly different magnitudes (−0.22 ppmv decade-1 and −0.08 ppmv decade-1, respectively).

Mengchu Tao et al.
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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Mengchu Tao et al.
Mengchu Tao et al.
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Short summary
This paper examines the annual and inter-annual variations as well as long-term trend of modelled stratospheric water vapor with a Lagrangian chemical transport model driven by ERA-I, MERRA-2 and JRA-55. We find reasonable consistency among the annual cycle, QBO and the variabilities induced by ENSO and volcanic aerosols. The main discrepancies are linked to the differences in reanalysis upwelling rates in the lower stratosphere. The trends are sensitive to the reanalyses that drives the model.
This paper examines the annual and inter-annual variations as well as long-term trend of...
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