Ocean temperature and salinity components of the Madden–Julian oscillation observed by Argo floats
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New diagnostics of the Madden–Julian oscillation (MJO) cycle in ocean temperature and, for the first time, salinity are presented. The MJO composites are based on 4 years of gridded Argo float data from 2003 to 2006, and extend from the surface to 1,400 m depth in the tropical Indian and Pacific Oceans. The MJO surface salinity anomalies are consistent with precipitation minus evaporation fluxes in the Indian Ocean, and with anomalous zonal advection in the Pacific. The Argo sea surface temperature and thermocline depth anomalies are consistent with previous studies using other data sets. The near-surface density changes due to salinity are comparable to, and partially offset, those due to temperature, emphasising the importance of including salinity as well as temperature changes in mixed-layer modelling of tropical intraseasonal processes. The MJO-forced equatorial Kelvin wave that propagates along the thermocline in the Pacific extends down into the deep ocean, to at least 1,400 m. Coherent, statistically significant, MJO temperature and salinity anomalies are also present in the deep Indian Ocean.
KeywordsIntraseasonal oscillation MJO Equatorial Kelvin wave Argo Salinity
These data were collected and made freely available by the International Argo Project and the national programs that contribute to it (http://www.argo.ucsd.edu and http://argo.jcommops.org). Argo is a pilot program of the Global Ocean Observing System. The interpolated OLR, NCEP Reanalysis, and NOAA interpolated sea surface temperature data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their web site at http://www.cdc.noaa.gov/. The TAO buoy data were provided by the TAO Project Office of NOAA/PMEL from their web site at http://www.pmel.noaa.gov/tao/index.shtml. The Wheeler and Hendon MJO index data were provided by Matt Wheeler, from the Australian Bureau of Meteorology website at http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/index.htm. PS studentship was partially funded by the Thai government. We thank two anonymous reviewers whose comments helped to improve the manuscript.
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