Secular changes of tropical rainfall regimes

Abstract Secular changes are demonstrated by residual mass curves. It is shown that tropical rainfall decreased abruptly at the end of the 19th century. This was due largely to a contraction of the rainy belt and a shortening of the wet seasons. In the SE. Asian monsoon region the annual rainfall has varied less than in the rest of the tropics but changes occurred in the seasonal pattern. Similarities in the records suggest a physical connection between frontal or cyclonic activity in the temperate zone and the October‐March monsoon rains of tropical Australia and SE. Asia. A concluding section develops the argument that the evaporation‐precipitation cycle is a partly unstable process and that small radiative changes could conceivably produce large and abrupt changes in the rainfall regime.