Observed changes in the lifetime and amplitude of the Madden–Julian Oscillation associated with interannual ENSO sea surface temperature anomalies

Pohl, Benjamin and Matthews, Adrian J. ORCID: https://orcid.org/0000-0003-0492-1168 (2007) Observed changes in the lifetime and amplitude of the Madden–Julian Oscillation associated with interannual ENSO sea surface temperature anomalies. Journal of Climate, 20 (11). pp. 2659-2674. ISSN 0894-8755

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Abstract

The Madden-Julian Oscillation (MJO) is analysed using the reanalysis zonal wind and satellite outgoing longwave radiation-based indices of Wheeler and Hendon for the 1974-2005 period. The average life time of MJO events varies with season, being 36 days for events whose central date occurs in December, and 48 days for events in September. The life time of the MJO in the equinoctial seasons (March-May and October-December) is also dependent on the state of the El Nino-Southern Oscillation (ENSO). During October-December it is only 32 days under El Nino conditions, increasing to 48 days under La Nina conditions, with similar values in northern spring. This difference is due to faster eastward propagation of the MJO convective anomalies through the Maritime Continent and western Pacific during El Nino, consistent with theoretical arguments concerning equatorial wave speeds. The analysis is extended back to 1950 by using an alternative definition of the MJO based on just the zonal wind component of the Wheeler and Hendon indices. A rupture in the amplitude of the MJO is found in 1975, at the same time as the well known rupture in the ENSO time series, that has been associated with the Pacific Decadal Oscillation. The mean amplitude of the MJO is 16% larger in the post-rupture period (1976-2005) compared to the pre-rupture period (1950-1975). Before the 1975 rupture, the amplitude of the MJO is a maximum (minimum) under El Nino (La Nina) conditions during northern winter, and a minimum (maximum) under El Nino (La Nina) conditions during northern summer. After the rupture, this relationship disappears. When the MJO-ENSO relationship is analysed using all year round data, or a shorter data set, as in some previous studies, no relationship is found.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Mathematics (former - to 2024) Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Volcanoes@UEA (former - to 2018) Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Meteorology, Oceanography and Climate Dynamics (former - to 2017) Faculty of Science > Research Groups > Climate, Ocean and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Fluids & Structures Faculty of Science > Research Groups > Numerical Simulation, Statistics & Data Science
Depositing User:	Vishal Gautam
Date Deposited:	18 Mar 2011 14:52
Last Modified:	07 Nov 2024 12:34
URI:	https://ueaeprints.uea.ac.uk/id/eprint/20927
DOI:	10.1175/JCLI4230.1

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