Shallow Convection in the MJO

Evolution of shallow convection through the life cycle of the Madden-Julian Oscillation (MJO) over the Indian and western Pacific Ocean is documented in this study. Shallow precipitating and non-precipitating clouds observed by mm cloud radars at Gan Island during the 2011-12 field campaign and at the Manus Island ARM TWP site for 10 years are diagnosed. Large-scale convective episodes at Manus are grouped into MJO and non-MJO events. Evolution of radar-observed shallow convective clouds and sounding-observed wind, humidity, and temperature leading to both MJO and non-MJO convective peaks are compared. Differences between MJO and non-MJO convective events are substantial in zonal wind and temperature, but subtle in humidity and shallow clouds. This suggests that humidity and shallow clouds may be instrumental to convective development in general but do not play any unique role in the MJO.