Decadal change of tropical precipitation associated with Indo-Pacific zonal oscillation

Knowledge of the global precipitation variability in the recent warming period is important for understanding future change of precipitation when the warming aggregates. Using the best available global precipitation dataset from 1979 to 2008, we show that the global precipitation variability beyond ENSO time scale features a prominent rapid transition in the late-1990s associated with an eastern Pacific triangle cooling. This transition determines the precipitation trend over the past 30 years, which is characterized by increased precipitation over the Indo-Pacific warm pool and decreased rainfall in the eastern Pacific. Both the interannual variation and the trend of the tropical rainfall is associated with an Indo-Pacific Zonal Oscillation (ZO) in sea-level pressure between the subtropical eastern Pacific and Asian-Australian monsoon region that is coupled with equatorial symmetric, zonal SST gradients across the Pacific basin. We argue that the ZO may be primarily maintained by a global–scale positive atmosphere-ocean feedback process. Thus, the global precipitation trend over the past 30-year warming period is largely a natural variation rooted in the internal feedback process.