Comparison of the Madden-Julian oscillation (MJO) during the TOGA COARE IOP with a 15-year climatology

Abstract

During the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) intensive observing period (IOP) (November 1992 to February 1993), two pronounced Madden-Julian oscillation (MJO) events were observed and have been intensively studied. To provide a necessary climatological basis for the case study as well as to evaluate how typical the COARE MJO cases are and to what degree conclusions made from these cases can be generalized, we compare the MJOs that occurred during the COARE IOP with a 15-year climatology. In this paper, along with a description of the characteristics of large-scale background including flow patterns, OLR and SST, the emphasis is placed on the intensity and propagation of the oscillations exhibited in organized convection and atmospheric circulation. Moreover, the maintenance of perturbation kinetic energy (PKE) associated with 30- to 60-day variability containing the MJOs is compared as well. The COARE IOP occurred in a lingering period between the persistence and the rejuvenation of the warm ENSO episode of 1992-1993. The intraseasonal oscillations in the convective activity and large-scale circulation are intensified during the IOP, and the maximum intensification is located in the region of central Pacific. Two MJO events in the COARE IOP are typical in terms of phase propagation. The major features of the energy transformation processes, such as the predominant role of the generation of the perturbation available potential energy (PAPE) by convective heating and its conversion into the PKE in the maintenance of the MJOs, found in the COARE IOP, are also displayed in the climatology indicating the generality of the results obtained from the COARE case study. Copyright 2000 by the American Geophysical Union.