| 英文摘要: | On a year-to-year basis the variability of sea surface temperature (SST) in the tropical Pacific is dominated by El Nino/Southern Oscillation (ENSO) events, which are known to influence weather patterns worldwide and have significant impacts on the US. But tropical Pacific SSTs can also vary more slowly, and tropical Pacific decadal variability (TPDV) has also been proposed as the cause of worldwide impacts including the great Dust Bowl drought of the 1930s and the recent global warming hiatus. The present work examines the possibility that some portion of TPDV is related to ENSO activity through a mechanism referred to as rectification, in which the ocean currents and ocean temperature anomalies associated with ENSO events, despite their transient nature, nevertheless produce a lasting rearrangement of heat across the tropical Pacific ocean. The sense of the rearrangement is such that ENSO rectification leads to cooler temperatures in the West Pacific "warm pool", the region of maximum SSTs around the Maritime Continent, and the "cold tongue" region along the equator in the eastern Pacific. The PI hypothesizes that if ENSO is unusually active for an extended period the rectification effect will lead to a mean state with a weaker east-west ocean temperature contrast across the equatorial Pacific, which is less favorable to ENSO. The result will be a reduction in ENSO activity, resulting in a weaker rectification effect that will lead to a stronger east-west temperature contrast. The stronger temperature contrast is more favorable to ENSO activity, producing a return to greater ENSO activity and repeating the cycle. A suite of experiments using a climate model in various configurations, including some with surface winds imposed on the ocean component model and others with SSTs imposed on the atmospheric component model, will be used to test the hypothesis.
In addition to its scientific interest, the question of TPDV origins has substantial societal implications. If the proposed mechanism contributes to TPDV and decadal modulation of ENSO activity, it may lead to improved prediction of ENSO events and slower variations of Pacific SST. Such predictions would be of great value given the worldwide impacts of tropical Pacific SST variations. The work may also be helpful in understanding the global warming hiatus and anticipating its termination. In addition, the work will support and train a graduate student, thereby developing the future workforce in this research area. |