The Reliability of Antarctic Tropospheric Pressure and Temperature in the Latest Global Reanalyses

• Published in: Journal of climate Vol. 25; no. 20; pp. 7138 - 7146
• Main Authors: Bracegirdle, Thomas J., Marshall, Gareth J.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15.10.2012
• Subjects: Air temperature; Analysis; Antarctic regions; Antarctic temperatures; Bias; Climate system; Climatology; Correlations; Datasets; Dynamic height; Earth, ocean, space; Energy balance; Exact sciences and technology; External geophysics; Geopotential; Geopotential height; Height; Mean sea level; Orography; Radiosonde data; Radiosondes; Resolution; Sea level; Sea level pressure; Studies; Summer; Surface energy; Surface energy balance; Surface properties; Surface temperature; Surface-air temperature relationships; Temperature; Trends; Weather; Winter; polar regions; Antarctica; Western Hemisphere; Eastern Hemisphere; Data analysis; Geopotential height; Bias; reliability; Sea level pressure; Surface temperature; coastal zone; Meteorological station; Atmospheric temperature; Observation data; Reanalysis; Polar region; Radio sounding
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-11-00685.1

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 (H 500), and 500-hPa temperature (T 500). It was found that CFSR and MERRA are of a sufficiently high resolution for the height of the orography to be accurately reproduced at coastal observation stations. Progressively larger negativeTs 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, and MERRA(11.1°, 10.2°, and 7.9°C, respectively) at Amundsen–Scott and Vostok, which have been linked to problems with representing the surface energy balance. Linear trends in the annual-meanT 500andH 500averaged 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 bothT 500andH 500). 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 andH 500trends at station locations.