The El Nino-Southern Oscillation and the Signal-to-Noise Paradox

自诞生以来，大气气候模型的分辨率在几十年来不断提高，现在全球通常以50 - 100公里的分辨率运行。然而，观测到的气候的代表性尚未完全收敛，误差仍然存在。已经提出了几种流体动力学机制，用于在当前模型分辨率下保留哪些缺失效应，并且随着计算能力的增长和允许更高的分辨率，这是一个活跃的研究领域。一个这样的过程是“涡流反馈”，即小尺度的涡流和波对大气环流中的大尺度特征产生积极的反馈。例如，这种反馈被认为对维持大西洋急流很重要。这一过程是通过大气中动量和涡度的涡动通量发生的，但最近的研究表明，在目前的大气环流模式中，当以气候分辨率运行时，它太弱了。该项目将使用一系列气候模式分辨率来量化这些不足，并研究其对长期预报和气候变化的影响，该项目将测试当气候模式分辨率提高时，对海洋表面温度和海冰覆盖的强加条件的更大气候响应。该项目将使用我们最新的高分辨率全球模式（~12公里分辨率）研究区域气候模拟中的涡动反馈。它将首先利用现有的模拟，但也有范围为学生进行新的模拟，以进一步测试的想法与合作伙伴科学家在气象局。将计算和检查用于确定涡流反馈强度的措施，提供一个机会，以获得在气候动力学这一重要和知之甚少的领域的专业知识。预计该项目将特别侧重于模型分辨率对模拟海面温度和海冰异常对大西洋急流的影响的重要性。这项工作的潜在影响是巨大的，因为季节性的，十年期的，甚至更长的气候预测都可能受到当前气候模式中缺乏涡流反馈的影响。在主管的支持下，候选人将有机会塑造项目设计，专注于他们最感兴趣的问题的各个方面。一个可能的研究领域是大气层对北极海冰损失的反应。该项目可以对扰动海冰进行非常高分辨率的模拟，并将其与作为国际极地放大模型相互比较项目的一部分在其他地方进行的“标准”分辨率实验进行比较。

Atmospheric climate models have increased in resolution over several decades since their inception and now typically run at 50-100km resolution globally. However, the representation of observed climate has not yet fully converged and errors remain. Several fluid dynamical mechanisms have been proposed for what missing effects remain at current model resolutions and this is an active research area as computing power grows and permits yet higher resolution. One such process is 'eddy feedback', whereby small scale eddies and waves feedback positively on large-scale features in the atmospheric circulation. Such a feedback is thought to be important in maintaining the Atlantic jet stream, for example. This process occurs through eddy fluxes of momentum and vorticity in the atmosphere, but recent studies suggest it is too weak in current general circulation models when run at climate resolution. This project will quantify these deficits using a range of climate model resolutions and investigate its implications for long-range forecasting and climate change.This project will test for a greater climate response to imposed conditions in the sea surface temperature and sea ice cover when climate model resolution is increased. The project will investigate eddy feedback in regional climate simulations using our latest high-resolution global models (~12km resolution). It will first make use of existing simulations, but there is also scope for the student to perform new simulations to further test ideas in collaboration with CASE partner scientists at the Met Office. Measures for determining the strength of eddy feedback will be calculated and examined, providing an opportunity to gain expertise in this important and poorly understood area of climate dynamics. It is anticipated that the project will focus particularly on the importance of model resolution for simulating the effects of sea surface temperature and sea ice anomalies on the Atlantic jet stream. The potential implications of this work are large because seasonal, decadal and perhaps even longer climate predictions could all be affected by a lack of eddy feedback in current climate models. With support from the supervisors, the candidate will have the opportunity to shape the project design to focus on aspects of the problem of most interest to them. One area of potential study could be the atmospheric response to Arctic sea-ice loss. The project could perform very high-resolution simulations with perturbed sea ice and compare these to 'standard' resolution experiments being run elsewhere as part of the international Polar Amplification Model Intercomparison Project.