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

大气气候模式自建立以来，在过去几十年中分辨率不断提高，目前在全球范围内的分辨率通常为50-100公里。然而，观测到的气候的表示尚未完全收敛，误差仍然存在。对于在当前模型分辨率下仍然存在的缺失效应，已经提出了几种流体动力学机制，随着计算能力的增长和更高分辨率的实现，这是一个活跃的研究领域。其中一个过程是“涡流反馈”，即小尺度的涡流和波浪对大气环流的大尺度特征有积极的反馈。例如，这种反馈被认为对维持大西洋急流很重要。这个过程通过大气中动量和涡度的涡流通量发生，但最近的研究表明，当以气候分辨率运行时，目前的一般环流模式的作用太弱。本项目将使用一系列气候模式分辨率对这些赤字进行量化，并研究其对长期预测和气候变化的影响。当气候模式分辨率提高时，该项目将测试对海面温度和海冰覆盖施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流反馈。它将首先利用现有的模拟，但也有空间让学生进行新的模拟，以进一步测试与英国气象局的CASE伙伴科学家合作的想法。将计算和检查确定涡旋反馈强度的措施，为在这一重要但知之甚少的气候动力学领域获得专门知识提供机会。预计该项目将特别关注模式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、年代际甚至更长时间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。在导师的支持下，候选人将有机会将项目设计的重点放在他们最感兴趣的问题方面。一个潜在的研究领域可能是大气对北极海冰损失的反应。该项目可以对受扰动的海冰进行非常高分辨率的模拟，并将这些模拟结果与其他地方正在进行的“标准”分辨率实验进行比较，这是国际极地放大模式比对项目的一部分。

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.