The Globally Coherent Pattern of Autumn Monsoon Precipitation

Abstract Over most tropical land areas, the annual peak in precipitation occurs during summer, associated with local monsoon circulation. However, some coastal regions tropics bulk of autumn, after low-level summer westerlies have abated. Examples include Nordeste region Brazil, southeastern India and Sri Lanka, Tanzania. Unlike equatorial regions, they receive little rainfall spring. Such are present along eastern coasts nearly all continents, suggesting that comprise a coherent yet previously unrecognized global phenomenon. In this study, we identify eight locations experience an “autumn monsoon” show unusual seasonal cycle is generated by similar mechanisms these. When these their rainfall, lie poleward ITCZ easterly winds. The spatial structure can be explained placement to east mountain ranges organize moist convection on windward sides. orographic forcing alone cannot explain unique cycle: despite similarities wind direction, surface humidity, sea temperatures (SSTs) between autumn spring, significantly more than We due differences large-scale atmospheric stability equinoctial seasons, which captured relative SST metric influenced SSTs remote upwelling zones Pacific Atlantic Oceans.