Observed Role of Soil Moisture on the MJO Precipitation in the Maritime Continent

The Madden-Julian oscillation (MJO) and its associated precipitation in the Maritime Continent are influenced by a complex interplay of factors, including soil moisture, topography, and vegetation, among others. In this study, we explore the role of soil moisture on the magnitude and distribution of precipitation as the MJO propagates across the Maritime Continent using available observations. Our analysis using Soil Moisture Active-Passive (SMAP) satellite data from 2015 to 2022 reveals significant intraseasonal variability in soil moisture, with a 3-day lag relative to precipitation across the Maritime Continent. Notably, within the intraseasonal timeframe, a 13-day negative correlation is also observed between soil moisture and precipitation, indicating that a decrease in soil moisture often precedes precipitation events. The results from the EOF analysis of soil moisture reveal pronounced intraseasonal variability, primarily influenced by the MJO, suggesting that a reduction in soil moisture in the Maritime Continent generally precedes MJO phases 1 and 2, where convection is enhanced over the Indian Ocean and suppressed over the eastern Maritime Continent and western Pacific regions by approximately two weeks. The implications of these results in the SM-precipitation relationship are discussed.