Historical SAM Variability. Part I: Century-Length Seasonal Reconstructions.

Jones, J. M., Fogt, R. L., Widmann, M., Marshall, G. J., Jones, P. D. and Visbeck, Martin (2009) Historical SAM Variability. Part I: Century-Length Seasonal Reconstructions. Open Access Journal of Climate, 22 (20). pp. 5319-5345. DOI 10.1175/2009JCLI2785.1.

[img]
Preview
Text
2009JCLI2785.pdf - Published Version

Download (4Mb)

Supplementary data:

Abstract

Seasonal reconstructions of the Southern Hemisphere annular mode (SAM) index are derived to extend the record before the reanalysis period, using station sea level pressure (SLP) data as predictors. Two reconstructions using different predictands are obtained: one [Jones and Widmann (JW)] based on the first principal component (PC) of extratropical SLP and the other (Fogt) on the index of Marshall. A regional-based SAM index (Visbeck) is also considered.These predictands agree well post-1979; correlations decline in all seasons except austral summer for the full series starting in 1958. Predictand agreement is strongest in spring and summer; hence agreement between the reconstructions is highest in these seasons. The less zonally symmetric SAM structure in winter and spring influences the strength of the SAM signal over land areas, hence the number of stations included in the reconstructions. Reconstructions from 1865 were, therefore, derived in summer and autumn and from 1905 in winter and spring.
This paper examines the skill of each reconstruction by comparison with observations and reanalysis data. Some of the individual peaks in the reconstructions, such as the most recent in austral summer, represent a full hemispheric SAM pattern, while others are caused by regional SLP anomalies over the locations of the predictors. The JW and Fogt reconstructions are of similar quality in summer and autumn, while in winter and spring the Marshall index is better reconstructed by Fogt than the PC index is by JW. In spring and autumn the SAM shows considerable variability prior to recent decades.

Document Type: Article
Keywords: Oceanography; Climatology; southern annular mode; sea-level pressure; antarctic oscillation index; hemisphere climate-change; ncep-ncar reanalysis; extratropical circulation; mean state; trends; temperature; patterns;
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/2009JCLI2785.1
ISSN: 0894-8755
Projects: Future Ocean
Date Deposited: 11 Feb 2011 12:14
Last Modified: 24 Aug 2017 10:37
URI: http://oceanrep.geomar.de/id/eprint/9488

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...