Eddy-Jet Interaction and Climate

在气候变化的背景下，探测大气环流和示踪剂全球输送的长期调制十分重要，但由于信噪比低，因此很难做到这一点。中村博士将通过在涡流和背景流及其相互作用之间引入新的分区来缓解这个问题。使用这种新的方法已经获得了初步的结果，并揭示了全球，多年的放大的涡旋和喷流，在2001年至2005年期间。使用传统方法无法检测到这种扩增。这一方法将用于气象分析和全球变暖情景下的长期气候模型模拟，以测量大气环流调制的频率和强度。将采用理想化模型（浅水和两层模型）来探讨这种调制的动力学基础，将使用被动示踪剂研究喷流及其调制对全球混合特性的影响，该示踪剂受所观测到的大尺度流动和小尺度扩散的平流作用。示踪剂方差的衰减率是全球混合的一个度量标准，将用一种新的诊断方法来量化急流区对衰减率的贡献，拟议的活动将为对流层环流和输送提供一个新的诊断平台，适合于探测气候状况的长期变化。拉格朗日平均方法绕过了传统意义上的涡平均流相互作用的复杂性，它允许在非保守processes.The更广泛的影响，这一活动的诊断框架可以应用于广泛的一类流，包括平流层，对流层，可能的海洋，和数值模拟方面的简单的解释。将资助两名研究生。

In the context of climate change, detecting long-term modulations in the general circulation and in the global transport of tracers is important, but it is made difficult by the low signal-to-noise ratio. Dr. Nakamura will alleviate this problem by introducing a new partition between the eddies and the background flow and their interaction. Preliminary results using this novel method have been obtained, and a global, multi-year amplification of the eddies and jets, over the period 2001-5 is revealed. This amplification is not detected using traditional methods. This method will be applied to meteorological analyses and to long-term climate-model simulations under global warming scenarios, to measure the frequency and intensity of modulations of the general circulation. Idealized models (shallow water and two-level models) will be employed to explore the dynamics that underlies such modulations.The effects of jets and their modulations on global mixing properties will be studied using a passive tracer subject to advection by the observed large-scale flow together with small-scale diffusivity. The decay rate of the variance of the tracer is a metric of global mixing, and contributions from the jet regions to the decay rate will be quantified with a new diagnostic.The proposed activity will provide a new diagnostic platform for the tropospheric general circulation and transport, suitable for the detection of long-term shifts in the climatic regime. The Lagrangian-mean approach bypasses the complication of eddy-mean flow interaction in the traditional sense, and it allows simpler interpretations in terms of nonconservative processes.The broader impacts of this activity are that the diagnostic framework can be applied to a wide class of flows, including the stratosphere, troposphere, possibly the oceans, and numerical simulations. Two graduate students will be supported.