Dependence of Precipitation on Precipitable Water Vapor Over the Maritime Continent and Implications to the Madden‐Julian Oscillation

The weakening of the Madden‐Julian Oscillation (MJO) as it propagates over the Maritime Continent (MC) is often referred to as the MC barrier. Here, we use 3‐hourly precipitable water vapor (PWV) data obtained from the Sumatran GPS Array and the ERA5 reanalysis to investigate the role played by the column moisture over the MC. Over Sumatra and the whole MC, we find a stronger dependence of precipitation on PWV over the ocean as compared to both inland and coastal regions. The MJO modulates the PWV over the ocean and over the MC by roughly the same amount, and the weaker precipitation variations over the MC between the MJO phases may be interpreted in terms of its weaker dependence on PWV over the MC. This different precipitation dependence on column moisture between the MC and the ocean may contribute to the MC barrier effect. Plain Language Summary The Madden‐Julian Oscillation (MJO) is the dominant intraseasonal variability in the tropical atmosphere, and also influences the global climate and weather, including the El Nino‐Southern Oscillation and the North Atlantic Oscillation. However, the reason behind why the MJO weakens or terminates as it propagates over the Maritime Continent remains unclear. Based on the idea that the rainfall is highly sensitive to the water vapor in the troposphere, we examine observations and reanalysis data. We find a weaker dependence of rainfall on column water vapor over the Maritime Continent than over the oceans, which may provide a simple interpretation of the smaller changes of rainfall over land associated with the MJO. Key Points The dependence of precipitation on precipitable water vapor is stronger over ocean than over the Maritime Continent The Madden‐Julian Oscillation (MJO) modulates the precipitable water vapor over the ocean and over the Maritime Continent by roughly the same amount Weaker precipitation variations over the Maritime Continent between the MJO phases may be explained by the weaker water vapor dependence