Monday, 23 January 2012: 2:00 PM
What Drive Decadal Variability of Global Precipitation?
Room 355 (New Orleans Convention Center )
Knowledge of the global precipitation variability in recent warming period is critical for understanding the 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 shift around late-1990s associated with an eastern Pacific triangle cooling. This climate shift determines the trend pattern of precipitation, which is characterized by increased precipitation over the Indo-Pacific warm pool and decreased rainfall in the eastern Pacific. We show that both the interannual variation and multi-decadal 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.
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