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| Titel |
Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses |
| VerfasserIn |
Z. D. Lawrence, G. L. Manney, K. Minschwaner, M. L. Santee, A. Lambert |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-13), S.3873-3892 |
| Datensatznummer |
250119624
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| Publikation (Nr.) |
 copernicus.org/acp-15-3873-2015.pdf |
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| Zusammenfassung |
| We present a comprehensive comparison of polar processing diagnostics derived from the National
Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research
and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF)
Interim Reanalysis (ERA-Interim). We use diagnostics that focus on meteorological conditions
related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics,
and air parcel trajectories to evaluate the effects these reanalyses might have on polar
processing studies. Our results show that the agreement between MERRA and ERA-Interim changes
significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases
improves. By comparing our diagnostics during five time periods when an increasing number of
higher-quality observations were brought into these reanalyses, we show how changes in the data
assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many
of our stratospheric temperature diagnostics show a convergence toward significantly better
agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational
Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as
the winter mean volume of air with temperatures below polar stratospheric cloud formation
thresholds (VPSC) and some diagnostics of polar vortex size and strength, do not show
improved agreement between the two reanalyses in recent years when data inputs into the DAS
were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim
agree much better than those calculated from earlier reanalysis data sets. We still, however,
see fairly large differences in many of the diagnostics in years prior to 2002, raising
the possibility that the choice of one reanalysis over another could significantly influence
the results of polar processing studies. After 2002, we see overall good agreement among the
diagnostics, which demonstrates that the ERA-Interim and MERRA reanalyses are equally appropriate
choices for polar processing studies of recent Arctic and Antarctic winters. |
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