Linkages between MJO and summer monsoon rainfall over India and surrounding region

Abstract

Satellite retrievals show a dipole-like pattern in composites of summer monsoon rainfall anomalies between the Indian region and the equatorial Indian Ocean (EIO) during the active (RMM phases 3, 4, 5, and 6) and suppressed phases (7, 8, 1, and 2) of the Madden Julian Oscillation (MJO). The north-eastern part of India shows an out-of-phase relationship with rest of the Indian land during different MJO phases. Moisture convergence anomalies largely explain the rainfall anomalies seen during the various MJO phases. Cyclonic wind anomalies are seen over eastern Arabian sea and the Bay of Bengal during active MJO phases. Positive (negative) rainfall anomalies are associated with positive (negative) CAPE anomalies over most parts of the Indian land, whereas there is an inverse relationship over the east coast of India. Timings of diurnal rainfall peaks are fairly robust across various MJO phases; however, the amplitudes vary significantly depending on the MJO phase and location. Some of the previously reported diurnal features, such as the propagation of convective systems over the Bay of Bengal from the west coast into the central and south Bay, are fairly robust across MJO phases. Convective systems forming over Sumatra and propagating into the eastern EIO are prominent during the suppressed and weak MJO periods, but not during the active period.