Variable Resolution Modeling of the Large-Scale Atmospheric Circulation Response to North Atlantic Sea-Surface Temperature (SST) Anomalies

大尺度大气环流对北大西洋海面温度 (SST) 异常响应的可变分辨率建模

基本信息

批准号：
2128409
负责人：
David Battisti
金额：
$ 34.12万
依托单位：
University of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-11-15 至 2024-10-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128409&HistoricalAwards=false
关键词：
Variable Resolution Modeling Large Scale

项目摘要

The extent to which the atmospheric circulation responds to changes in the underlying sea surface temperature (SST) is a central topic in climate dynamics. In the tropics the response of atmospheric circulation to SST variability is easily seen in the evolution of El Nino events. But in the middle and high latitudes there is no comparably strong and unambiguous attribution of circulation change to variations in underlying SST. Nevertheless recent research suggests that SST variability associated with the meandering of the Gulf Stream affects the decade-to-decade variability of the wintertime atmospheric circulation over much of the Northern Hemisphere. The observational evidence is suggestive but not conclusive, as the inherent noisiness of circulation variability and the short length of the observational record do not permit definitive attribution. Climate model simulations offer a way around the shortness of the observed record, along with the ability to design controlled experiments, and models using moderate resolution (say one gridpoint per degree of latitude and longitude) can generate very long simulations. But such simulations have not generally shown a circulation response to Gulf Stream SST variations, and recent experiments suggest that much higher resolutions are necessary to capture the physics and dynamics leading to the circulation response. Unfortunately global simulations using such high resolutions are too computationally intensive to permit in-depth experimentation.Research under this award considers the effects of Gulf Stream SST variations using a variable resolution (VR) model in which the grid spacing over most of the world is one degree but resolution over the Arctic and northern North Atlantic is increased to 1/8th degree, or about 12km between gridpoints. The model is a version of the Community Atmosphere Model (CAM), the atmospheric component model of the Community Earth System Model (CESM). Preliminary results show a robust hemispheric circulation response, with a spatial pattern similar to the North Atlantic Oscillation, forced by an imposed SST change representative of a Gulf Stream fluctuation. Further work compares the VR-CAM simulations with CAM simulations at lower resolution to identify the physics and dynamics captured by the high resolution. One hypothesis is that higher resolution is necessary to capture the influence of SST change on the rising motions associated with frontal weather systems as they cross the Gulf Stream. A further goal of the project is to use machine learning to develop parameterizations of the small-scale effects captured in the VR simulations so that they can be represented approximately at coarser and less computationally intensive model resolutions.The work has societal relevance due to the desirability of better understanding of decade-to-decade changes in the wintertime circulation over the Northern Hemisphere. Recent work suggests that the decadal circulation variabililty is more predictable than would be expected based on climate model simulations, suggesting that models may be missing key ingredients needed for successful long-range predictions. The work performed here may thus contribute to the development of models capable of long-range predictions with substantial societal value. In addition, the project contributes to the development of VR-CAM, which will be made available to the worldwide community of CESM users and developers. The Principal Investigators conduct outreach to the public through the University of Washington Program on Climate Change, as well as the Science Communication Fellowship Program at the Pacific Science Center in Seattle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

大气环流对底层海面温度（SST）变化的响应程度是气候动力学的一个中心话题。在热带地区，大气环流对海温变化的响应在厄尔尼诺事件的演变中很容易看出。但在中高纬度地区，环流变化对底层海温变化的影响并不明显。然而，最近的研究表明，与墨西哥湾流蜿蜒相关的海温变化会影响北半球大部分地区冬季大气环流的十年到十年的变化。观测证据具有提示性，但不是结论性的，因为循环变化固有的噪音和观测记录的长度较短，不允许明确的归因。气候模型模拟提供了一种解决观测记录短暂性的方法，同时还能够设计受控实验，并且使用中等分辨率（例如每度纬度和经度一个网格点）的模型可以生成很长的模拟。但此类模拟通常并未显示出对墨西哥湾流海温变化的环流响应，并且最近的实验表明，需要更高的分辨率来捕获导致环流响应的物理和动力学。不幸的是，使用如此高分辨率的全球模拟计算量太大，无法进行深入的实验。该奖项的研究使用可变分辨率（VR）模型考虑了湾流海表温度变化的影响，其中世界大部分地区的网格间距为一度，但北极和北大西洋北部的分辨率增加到 1/8 度，即网格点之间约 12 公里。该模型是社区大气模型 (CAM) 的一个版本，社区大气模型 (CAM) 是社区地球系统模型 (CESM) 的大气成分模型。初步结果显示，半球环流响应强劲，其空间模式类似于北大西洋涛动，这是由代表墨西哥湾流波动的强加海温变化所迫使的。进一步的工作将 VR-CAM 模拟与较低分辨率下的 CAM 模拟进行比较，以识别高分辨率捕获的物理和动力学。一种假设是，需要更高的分辨率来捕捉海温变化对锋面天气系统穿过墨西哥湾流时相关上升运动的影响。该项目的另一个目标是利用机器学习来开发 VR 模拟中捕获的小规模效应的参数化，以便可以以更粗糙且计算密集度较低的模型分辨率来近似表示它们。由于期望，这项工作具有社会相关性更好地了解北半球冬季环流的十年间变化。最近的研究表明，年代际环流变化比基于气候模型模拟的预期更容易预测，这表明模型可能缺少成功进行长期预测所需的关键要素。因此，这里进行的工作可能有助于开发能够进行具有重大社会价值的长期预测的模型。此外，该项目还有助于 VR-CAM 的开发，VR-CAM 将提供给全球 CESM 用户和开发人员社区。首席研究员通过华盛顿大学气候变化项目以及西雅图太平洋科学中心的科学传播奖学金项目向公众进行推广。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。