Modulation of active-break spell of Indian summer monsoon by Madden Julian Oscillation

Abstract

The Madden Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly time scale and a major driver of Indian summer monsoon (ISM). In this study, using Indian Meteorological Department (IMD) high resolution daily gridded rainfall data and Wheeler-Hendon MJO indices, the daily rainfall distribution over India associated with various phases of eastward propagating MJO was examined to understand the MJO–monsoon rainfall relationship. The present study reveal that the onset of break and active events over India and the duration of these events are strongly related to the phase and strength of the MJO. The break events were relatively better associated with the strong MJO phases than the active events. About 80% of the break events were found to be set in during the phases 1, 2, 7 and 8 of MJO with maximum during phase 1 (34%). On the other hand, about 58% of the active events were set in during the MJO phases 3–6 with maximum during phase 6 (21%). The results of this study indicate an opportunity for using the real time information and skillful prediction of MJO phases for the extended range prediction of break and active conditions.