The Madden–Julian Oscillation Observed during the TOGA COARE IOP: Global View

Abstract

During the TOGA COARE Intensive Observing Period (November 1992?February 1993), two pronounced Madden?Julian oscillation (MJO) events associated with super cloud clusters and westerly wind bursts were observed. This paper presents a global view of the MJOs including the origin of the super clusters in the Indian Ocean, their migration into the Maritime Continent and the TOGA COARE large-scale soundings array (LSA) in the western equatorial Pacific, and their rapid decay over cold water of the eastern Pacific. The structure and evolution of the MJO are examined with emphasis on the coupling between large-scale motion and convection. Because of differences in propagation speeds, the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the MJO. However, the centers of deep convection always coincide with those of large-scale ascent. The super cloud cluster accompanies a wide area of warm air in the upper troposphere. Over the warm pool region the perturbation kinetic energy of the motion in the 30?60-day period range is maintained by the conversion of perturbation available potential energy generated by convective heating. Over the central-eastern Pacific, there is strong horizontal convergence of wave energy flux entering the equatorial upper-tropospheric westerly duct from the extratropical latitudes, suggesting interactions of the MJO with midlatitude disturbances.