The Effects of El Nino-Southern Oscillation (ENSO) on the Mean Climate State of the Tropical Pacific

厄尔尼诺-南方涛动（ENSO）对热带太平洋平均气候状态的影响

• 批准号: 0852329
• 负责人: De-Zheng Sun
• 金额: $ 41.07万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-15 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0852329&HistoricalAwards=false
• 关键词: Effects; El; Nino; Southern; Oscillation

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The El Niño-Southern Oscillation (ENSO) corresponds to a sloshing of water in the equatorial upper Pacific: during an ENSO cycle water moves back and forth north to south and east to west. This suggests that the time-mean effects of ENSO are to homogenize the upper ocean temperature, reducing the east-west and north-south gradients of sea surface temperature (SST). In more technical terms, it suggests that the eddy heat flux over ENSO cycles is a significant term in the long-term average heat budget of the equatorial upper Pacific. Moreover, it is plausible that the eddy heat flux is down gradient, such that it cools the warm pool, warms the thermocline, and warms the cold tongue.To test this hypothesis, a heat budget analysis will be carried out using reanalysis data, numerical experiments will be conducted using an ocean model and a full coupled climate model. Forced experiments will include subjecting two different ocean models to surface forcing including and excluding the ENSO signal, and to surface forcing with different levels or types of ENSO activity. Analyses of the heat-budgets in these numerical experiments will reveal the effects of ENSO on the mean state, the relationship between heat fluxes and the thermal variance, and the relationship between the eddy heat fluxes and the thermal gradients in the mean state. The coupled experiments are designed to understand and to evaluate the interaction between the level of ENSO activity and the mean state of the tropical Pacific. Three models of varying complexity will be used for the coupled experiments: the National Center for Atmospheric Research (NCAR) Pacific basin model coupled to an empirical atmospheric model, the NCAR global ocean model coupled to an empirical atmosphere, and the NCAR Community Climate System Model (CCSM).These studies will advance our understanding of the role of ENSO in maintaining the tropical Pacific climate on decadal or longer time-scales. On these time-scales, ENSO events are transients, whose time-mean effects have to be assessed. The resulting knowledge should offer insights into the causes of tropical biases in simulations by coupled climate models; it will improve understanding of tropical Pacific climate in past climates; and it will add to our understanding of how ENSO and the mean tropical Pacific climate will respond to global warming.Broader impacts of this research include an improved understanding of the role of ENSO-a phenomenon of great public interest-in the climate system. Through Dr. Sun's teaching and supervision of graduate and postdoctoral students, this research will contribute to the education, and training of future climate scientists.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。厄尔尼诺-南方涛动（ENSO）对应于赤道上太平洋的水晃动：在ENSO循环期间，水从北向南和从东向西来回移动。这表明，厄尔尼诺/南方涛动的时间平均效应是使上层海洋温度均匀化，减少海表温度的东西梯度和南北梯度。用更专业的术语来说，这表明ENSO循环中的涡动热通量是赤道上太平洋长期平均热收支中的一个重要项。此外，涡动热通量呈下降梯度，使暖池变冷，温跃层变暖，冷舌变暖，这一假说也是合理的，为了验证这一假说，将利用再分析资料进行热收支分析，并利用海洋模式和完全耦合气候模式进行数值试验。强迫实验将包括使两个不同的海洋模型受到包括和不包括厄尔尼诺/南方涛动信号的表面强迫作用，以及受到不同程度或类型的厄尔尼诺/南方涛动活动的表面强迫作用。通过对这些数值试验中热量收支的分析，可以揭示ENSO对平均状态的影响，以及平均状态下热通量与热方差的关系，涡动热通量与热梯度的关系。耦合实验的目的是了解和评估ENSO活动水平和热带太平洋的平均状态之间的相互作用。三个不同复杂程度的模式将被用于耦合实验：NCAR太平洋海盆模式耦合到一个经验大气模式，NCAR全球海洋模式耦合到一个经验大气模式，和NCAR社区气候系统模式（CCSM），这些研究将促进我们的理解ENSO在维持热带太平洋气候的十年或更长的时间尺度上的作用。在这些时间尺度上，ENSO事件是瞬变现象，其时间平均影响必须加以评估。由此产生的知识应有助于深入了解耦合气候模式模拟中热带偏差的原因;它将增进对过去气候中热带太平洋气候的了解;它将增加我们对ENSO和平均热带太平洋气候将如何应对全球变暖的理解。这项研究的更广泛影响包括提高对ENSO作用的理解--这是一种引起公众极大兴趣的现象--在气候系统中。通过孙博士对研究生和博士后的教学和指导，这项研究将有助于教育和培训未来的气候科学家。