The Maritime Continent, the region connecting the tropical Indian Ocean and the Western Pacific, is one of the wettest areas on Earth. The latent heat released from rainfall in the region drives atmospheric circulation throughout the tropics. Understanding the variability of rainfall over the Maritime Continent is critical to understanding regional and global climate. A recent study published in the Journal of Climate, looks at how the annual wet/dry seasonal behavior of the Maritime Continent region impacts the daily cycle of precipitation over the Maritime Continent. The research team, funded in part by CPO’s Climate Variability & Predictability (CVP) program, used observational analyses and high-resolution model simulations to investigate changes in the amplitude of the day/night cycle of precipitation from 1998 to 2014. The standard daily rainfall cycle in the Maritime Continent shows a strong peak in precipitation in the late afternoon, over land, and a moderatue peak in precipitation in the early morning, over the ocean. The researchers found that the cycle’s amplitude, or differences in behavior at different times, is statistically different between the Northern hemisphere winter and summer seasons. In the summer, precipitation amplitude is reduced by about a third, meaning the daily rainfall highs and lows are that much closer together. Using simulations to trace the reasons why, the study concludes that the seasonal mean background atmospheric moisture condition (aka is it wet-season or dry-season) is mostly responsible for the winter-summer differences.
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