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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-400
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
22 May 2017
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.
Reanalysis comparisons of upper tropospheric/lower stratospheric jets and multiple tropopauses
Gloria L. Manney1,2, Michaela I. Hegglin3, Zachary D. Lawrence2, Krzysztof Wargan4, Luis F. Millán5, Michael J. Schwartz5, Michelle L. Santee5, Alyn Lambert5, Steven Pawson4, Brian W. Knosp5, Ryan A. Fuller5, and William H. Daffer5 1NorthWest Research Associates, Socorro, NM USA
2New Mexico Institute of Mining and Technology, Socorro, NM USA
3University of Reading, Reading, UK
4NASA/Goddard Space Flight Center, Greenbelt, MD USA
5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Abstract. The representation of upper tropospheric/lower stratospheric (UTLS) jet and tropopause characteristics is compared in five modern high-resolution reanalyses for 1980 through 2014. Climatologies of upper tropospheric jet, subvortex jet (the lowermost part of the stratospheric vortex), and multiple tropopause frequency distributions in MERRA (Modern Era Retrospective Analysis for Research and Applications), ERA-I (the ECMWF interim reanalysis), JRA-55 (the Japanese 55-year Reanalysis), and CFSR (the Climate Forecast System Reanalysis) are compared with those in MERRA-2. Differences between alternate products from individual reanalysis systems are assessed; in particular, a comparison of CFSR data on model and pressure levels highlights the importance of vertical grid spacing. Most of the differences in distributions of UTLS jets and multiple tropopauses are consistent with the differences in assimilation model grids and resolution: For example, ERA-I (with coarsest native horizontal resolution) typically shows a significant low bias in upper tropospheric jets with respect to MERRA-2, and JRA-55 a more modest one, while CFSR (with finest native horizontal resolution) shows a high bias with respect to MERRA-2 in both upper tropospheric jets and multiple tropopauses. Vertical temperature structure and grid spacing are especially important for multiple tropopause characterization. Substantial differences between MERRA and MERRA-2 are seen in mid- to high-latitude southern hemisphere winter upper tropospheric jets and multiple tropopauses, and in the upper tropospheric jets associated with tropical circulations during the solstice seasons; some of the largest differences from the other reanalyses are seen in the same times and places. Very good qualitative agreement among the reanalyses is seen between the large scale climatological features in UTLS jet and multiple tropopause distributions. Quantitative differences may, however, have important consequences for transport and variability studies. Our results highlight the importance of considering reanalyses differences in UTLS studies, especially in relation to resolution and model grids; this is particularly critical when using high-resolution reanalyses as an observational reference for evaluating global chemistry climate models.

Citation: Manney, G. L., Hegglin, M. I., Lawrence, Z. D., Wargan, K., Millán, L. F., Schwartz, M. J., Santee, M. L., Lambert, A., Pawson, S., Knosp, B. W., Fuller, R. A., and Daffer, W. H.: Reanalysis comparisons of upper tropospheric/lower stratospheric jets and multiple tropopauses, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-400, in review, 2017.
Gloria L. Manney et al.
Gloria L. Manney et al.

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Short summary
Upper tropospheric/lower stratospheric (UTLS) jet stream and multiple tropopause distributions are compared among five state-of-the-art reanalyses. The reanalyses show very similar global distributions of UTLS jets, reflecting their overall high quality; slightly larger differences are seen in tropopause characteristics. Regional and seasonal differences, albeit small, may have implications for using these reanalyses for quantitative dynamical and transport studies focusing on the UTLS.
Upper tropospheric/lower stratospheric (UTLS) jet stream and multiple tropopause distributions...
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