This study investigates atmospheric water cycles over several timescales to understand the maintenance processes that control heavy precipitation over the islands of the Maritime Continent.

Large island regions can be divided into land, coastal, and ocean areas based on the characteristics of the hydrologic cycle and the diurnal variation in precipitation. Within the Maritime Continent, the major islands of Borneo and New Guinea exhibit different hydrologic cycles. Large-scale circulation variations, such as the seasonal cycle and the Madden-Julian oscillation, have a lesser effect on the hydrologic cycle over Borneo than over New Guinea because the effect attributes from their shapes and locations. On the other hand, the impact of diurnal variations on regional-scale circulation and water exchange between land and coastal regions is pronounced over both islands.

The recycling ratio of precipitation, which may be related to a stronger diurnal variation in the atmospheric water cycle that results from higher evapotranspiration over tropical rainforests, is higher over Borneo than over New Guinea.