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Abstract

The most widely accepted characterization of the Madden–Julian oscillation (MJO) is the bivariate index
developed by Wheeler and Hendon. This index relies in part on satellite-based observations of outgoing
longwave radiation and thus is not defined for the presatellite era. TheMJOis known to have a strong signature
in surface pressure, and daily measurements of this variable are available as far back as the late nineteenth
century. This study undertakes a statistical reconstruction of the Wheeler andHendonMJOindex from 1905 to
2008 based on tropical surface pressures estimated recently by the twentieth-century reanalysis project. The
temporal and spectral properties of the reconstructed index are first shown to be consistent with the Wheeler
and Hendon index over the common period (1979–2008). The reconstructed index is then validated over the
earlier period (1905–1978) by examining its relationship with cloud cover, surface wind, precipitation, and sea
level. These relationships are shown to be consistent with corresponding results obtained from theWheeler and
Hendon index over the shared period and stable over the earlier period. Finally, a simple damped harmonic
oscillator model is used to gain new insights into the predictability of the MJO index and also demonstrate
consistency between the reconstructed index and theWheeler andHendon index. These results give confidence
in the validity of the historical reconstruction of the MJO index over the last century.

Item Type:	Article
Authors/Creators:	Oliver, ECJ and Thompson, KR
Journal or Publication Title:	Journal of Climate
ISSN:	0894-8755
Additional Information:	Copyright 2012 The American Meteorological Society
Item Statistics:	View statistics for this item

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