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The reliability of Antarctic tropospheric pressure and temperature in the latest global reanalyses

Bracegirdle, Thomas J.; Marshall, Gareth J.. 2012 The reliability of Antarctic tropospheric pressure and temperature in the latest global reanalyses. Journal of Climate, 25 (20). 7138-7146. 10.1175/JCLI-D-11-00685.1

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Abstract/Summary

In this study, surface and radiosonde data from staffed Antarctic observation stations are compared to output from five reanalyses [Climate Forecast System Reanalysis (CFSR), 40-yr ECMWF Re-Analysis (ERA-40), ECMWF Interim Re-Analysis (ERA-Interim), Japanese 25-year Reanalysis (JRA-25), and Modern Era Retrospective-Analysis for Research and Applications (MERRA)] over three decades spanning 1979–2008. Bias and year-to-year correlation between the reanalyses and observations are assessed for four variables: mean sea level pressure (MSLP), near-surface air temperature (Ts), 500-hPa geopotential height (H500), and 500-hPa temperature (T500). It was found that CFSR andMERRAare of a sufficiently high resolution for the height of the orography to be accurately reproduced at coastal observation stations. Progressively larger negative Ts biases at these coastal stations are apparent for reanalyses in order of decreasing resolution. However, orography height bias cannot explain large winter warm biases in CFSR, JRA-25, andMERRA(11.18, 10.28, and 7.98C, respectively) at Amundsen–Scott and Vostok, which have been linked to problems with representing the surface energy balance. Linear trends in the annual-mean T500 andH500 averaged over Antarctica as a whole were found to be most reliable in CFSR, ERA-Interim, and MERRA, none of which show significant trends over the period 1979– 2008. In contrast JRA-25 shows significant negative trends over 1979–2008 and ERA-40 gives significant positive trends during the 1980s (evident in both T500 andH500). Comparison to observations indicates that the positive trend in ERA-40 is spurious. At the smaller spatial scale of individual stations all five reanalyses have some spurious trends. However, ERA-Interim was found to be the most reliable for MSLP andH500 trends at station locations.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1175/JCLI-D-11-00685.1
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Climate
ISSN: 0894-8755
Additional Information. Not used in RCUK Gateway to Research.: © Copyright 2012 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyright@ametsoc.org.
Date made live: 26 Nov 2012 12:29
URI: http://nora.nerc.ac.uk/id/eprint/20554

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