Moisture transport over the western Maritime Continent during the 2015 and 2017 YMC Sumatra campaigns in global cloud-system-resolving simulations

Abstract

Transport of moisture over the western Maritime Continent (MC) was examined using global cloud-system-resolving simulations for the Years of the Maritime Continent (YMC) field campaigns in 2015 and 2017, under peak El Niño and moderate La Niña conditions, respectively. We focused on the role of highand low-frequency variability in the moistening over land and ocean, and their relationship with intraseasonal oscillation (ISO) events. The period-mean profiles indicate moistening by lowfrequency upward motion in the deep troposphere and drying (moistening) in the lower (middle and upper) troposphere by highfrequency variability. The advection over ocean was greater in 2017 than in 2015, with the opposite occurring over land with smaller interannual differences. Over ocean, the roles of the highfrequency variability in the ISO life cycle, namely, the lower-tomiddle- tropospheric moistening (enhanced upward transport of moisture) during the preconditioning (active) phases of the ISO, were common in both years, while over land, the high-frequency effects were nearly in phase (not correlated) with the ISO in the 2015 (2017) case. These results highlight clear land-ocean contrasts in the sensitivity of local convection to the background state and its link with the ISO life cycle.