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

该奖项是根据2009年《美国复苏和再投资法》(公法111-5)提供资金的。厄尔尼诺-南方涛动(ENSO)对应于赤道上太平洋的海水晃动：在ENSO周期中，水从北到南和从东到西来回移动。这表明，ENSO的时间平均效应是使上层海洋温度均一化，使海表面温度的东西向和南北向梯度减小。在更专业的术语中，它表明ENSO循环上的涡旋热通量是赤道上太平洋长期平均热量收支中的一个重要项。此外，涡旋热通量可能是向下梯度的，从而冷却暖池，升温温跃层，温暖寒冷的舌头。为了验证这一假设，将使用再分析数据进行热量平衡分析，并将使用海洋模式和全耦合气候模式进行数值试验。强迫实验将包括两个不同的海洋模型，包括包括和排除ENSO信号的表面强迫，以及不同水平或类型的ENSO活动的表面强迫。对这些数值试验中热量收支的分析将揭示ENSO对平均态的影响，热通量与热方差的关系，以及涡动热通量与平均态温度梯度的关系。这两个实验旨在了解和评估ENSO活动水平和热带太平洋平均状态之间的相互作用。三个复杂程度不同的模式将用于耦合实验：国家大气研究中心(NCAR)太平洋盆地模式与经验大气模式的耦合，NCAR全球海洋模式与经验大气的耦合，以及NCAR社区气候系统模式(CCSM)。这些研究将加深我们对ENSO在维持热带太平洋气候的年代际或更长时间尺度上的作用的理解。在这些时间尺度上，ENSO事件是瞬变的，其时间平均影响必须评估。由此产生的知识应该会在耦合气候模式的模拟中提供对热带偏差的原因的洞察；它将提高对过去气候中热带太平洋气候的理解；它将增加我们对ENSO和平均热带太平洋气候如何响应全球变暖的理解。这项研究的更广泛的影响包括对ENSO在气候系统中的作用的更好的理解--这是一种非常受公众关注的现象。通过孙博士对研究生和博士后的教学和指导，这项研究将为未来气候科学家的教育和培养做出贡献。

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.