Collaborative Research: Understanding Observed Low Frequency Variability of Sea-Surface Temperature (SST) in the North Atlantic

北大西洋海表温度（SST）在年际和年代际时间尺度上波动，具有不同的空间结构特征。 对这些变异模式的机制仍然知之甚少。 理论的不同在于它们对海洋环流和翻转环流的作用，最重要的是，它们是否涉及SST对大气环流的反馈。这些问题将使用一种新的方法来解决;交互式集合耦合全球气候模式（GCM），其中大气模式的集合耦合到海洋模式的单一实现。 给定一个足够大的大气模式集合，基本上所有固有的大气噪声都通过平均去除，然后海洋由大气强迫驱动，其中只包括大气对SST的确定性响应。 然后，内在的大气变率表示为“天气噪声”，可以重新引入到耦合模拟在一个可控的方式。NCAR社区气候系统模式3（CCSM 3）的集合耦合版本将被实施，一组六个假设检验实验将进行。 “天气噪音”将使用观测和模式输出进行评估。 后一种情况是所谓的“完美模式”的研究，这将有助于评估的作用，观测和模式误差在使用观测派生的天气噪音。 类似地，模式与观测值的差异的重要性可以通过在第二个GCM的集合耦合版本中使用来自一个GCM的天气噪声来评估。 只有模式的研究将是有价值的，在研究模式的变化，涉及纬向翻转环流，因为这种模式发生在长时间尺度上不容易捕捉到的现存的观测record.Broader的影响是在使集合耦合CCSM 3提供给社会应用到气候预测和验证和改进耦合模式。 将对两名研究生进行耦合气候模型应用方面的培训。

Sea-surface temperatures (SST) in the North Atlantic fluctuate on interannual and on decadal timescales, with different characteristic spatial structures. The mechanisms responsible for these modes of variability remain poorly understood. Theories differ in the roles they ascribe to gyre and overturning circulations in the ocean, and, most importantly, in whether or not they involve feedbacks from the SST onto the circulation of the atmosphere.These issues will be addressed using a novel method; the interactive ensemble coupled global climate model (GCM), in which an ensemble of atmospheric models is coupled to a single realization of the oceanic model. Given a sufficiently large ensemble of atmospheric models, essentially all intrinsic atmospheric noise is removed by averaging, and the ocean is then driven by atmospheric forcing that includes only the deterministic response of the atmosphere to the SST. Intrinsic atmospheric variability denoted "weather noise" can then be reintroduced to the coupled simulations in a controlled way.An ensemble coupled version of the NCAR Community Climate System Model 3 (CCSM3) will be implemented, and a set of six hypothesis-testing experiments will be carried out. "Weather noise" will be evaluated using both observations and model output. The latter case is a so-called "perfect model" study, which will serve to evaluate the role of observational and model errors in using observationally derived weather noise. Similarly, the importance of model differences from observations can be evaluated by using weather noise derived from one GCM in the ensemble coupled version of a second GCM. Model-only studies will be valuable in studying modes of variability involving the meridional overturning circulation; as such modes occur on long timescales not readily captured by the extant observational record.Broader impacts are in making the ensemble coupled CCSM3 available to the community for application to climate prediction and to verifying and improving coupled models. Two graduate students will be trained in the application of coupled climate models.