Collaborative Research: A Teleconnection between the Tropical Madden-Julian Oscillation and Arctic Sudden Stratospheric Warming Events in Warm Climates

合作研究：热带马登-朱利安涛动与温暖气候下北极平流层突然变暖事件之间的遥相关

基本信息

批准号：
1826635
负责人：
Eli Tziperman
金额：
$ 41.17万
依托单位：
Harvard University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-07-01 至 2022-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1826635&HistoricalAwards=false
关键词：
Collaborative Research Teleconnection between Tropical

项目摘要

The wintertime winds of the Northern Hemisphere stratosphere form a vortex circulating around a cold low pressure cell over the Arctic. Occasionally, perhaps six time in a decade, the vortex experiences a major disruption known as a stratospheric sudden warming (SSW), in which the Arctic stratosphere warms by tens of degrees celsius in just a few days. SSWs are often followed by cold air outbreaks and other forms of severe weather, thus they are of practical as well as scientific interest. Classical studies of SSWs established that the breakdown of the vortex is caused by planetary-scale waves propagating upward and northward into the polar stratosphere. These waves can originate in various ways, and previous work by the PIs and others finds that some SSWs can be linked to the tropical Madden-Julian Oscillation (MJO). The MJO is a broad envelope of cloudiness and convective rainfall that forms over the equatorial Indian Ocean and propagates slowly eastward as far as the central Pacific. Planetary waves generated by the MJO are known to affect weather in middle and high latitudes but their effect on SSWs has not received much attention until recently. The MJO-SSW connection is of particular interest given recent studies suggesting that MJO activity increases when tropical sea surface temperatures (SSTs) increase. The increase in MJO activity suggests greater SSW frequency, but other factors such as changes in the jet streams in a warming climate must also be considered.This project examines the MJO-SSW connection in a hierarchy of models of varying degrees of complexity. The research is enabled by a specialized model configuration which is capable of simulating both the MJO, which is notoriously difficult to capture in current weather and climate models, and SSWs. The model uses superparameterization (SP), a technique pioneered by one of the PIs in which cloud resolving models are embedded in every grid column of a global model (see AGS-0425247). The SP technique is applied in the Community Atmosphere Model (CAM, the atmospheric component model of the Community Earth System Model), used here with enhanced vertical resolution to capture stratospheric dynamics. The work has broader impacts due to the effects of SSWs on surface weather in the Northern Hemisphere. The warming of tropical SSTs raises the prospect of stronger MJO events, and it is of practical interest to understand how stronger events will affect weather regimes over the US and other countries. Moreover, the slow propagation of the MJO offers some hope for extended-range prediction of extreme weather linked to SSWs, thus research on the MJO-SSW connection has implications for operational weather forecasting. The project has educational broader impacts through summer internships supporting undergraduates and local high school students, who are trained in python programming and atmospheric data analysis. The award also provides support and training to two graduate students, thereby providing for the future workforce in this research area.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.

北半球平流层的冬季风形成一个涡旋，围绕北极上空的寒冷低压单元循环。有时，涡旋可能会在十年内六次经历一次重大破坏，称为平流层突然变暖（SSW），即北极平流层在短短几天内升温数十摄氏度。南海风暴之后往往会出现冷空气爆发和其他形式的恶劣天气，因此它们具有实际意义和科学意义。对SSW的经典研究表明，涡旋的破裂是由向上和向北传播到极地平流层的行星尺度波引起的。这些波可能以多种方式产生，PI 和其他人之前的工作发现，一些 SSW 可能与热带马登-朱利安涛动 (MJO) 有关。 MJO 是一个由云层和对流降雨组成的广阔包层，在赤道印度洋上空形成，缓慢向东传播至太平洋中部。众所周知，MJO 产生的行星波会影响中高纬度地区的天气，但直到最近，它们对 SSW 的影响才受到足够的关注。最近的研究表明，当热带海面温度（SST）增加时，MJO 活动就会增加，因此 MJO-SSW 联系特别令人感兴趣。 MJO 活动的增加表明 SSW 频率更高，但还必须考虑其他因素，例如气候变暖时急流的变化。该项目在不同复杂程度的模型层次结构中检查 MJO-SSW 之间的联系。这项研究是通过专门的模型配置来实现的，该模型配置能够模拟 MJO（众所周知，在当前的天气和气候模型中很难捕获 MJO）和 SSW。该模型使用超参数化 (SP)，这是一项由 PI 之一首创的技术，其中云解析模型嵌入到全局模型的每个网格列中（请参阅 AGS-0425247）。 SP 技术应用于社区大气模型（CAM，社区地球系统模型的大气成分模型），此处使用增强的垂直分辨率来捕获平流层动力学。由于南海风暴对北半球地表天气的影响，这项工作具有更广泛的影响。热带海温变暖增加了 MJO 事件发生的可能性，了解更强的事件将如何影响美国和其他国家的天气状况具有实际意义。此外，MJO 的缓慢传播为与 SSW 相关的极端天气的大范围预测带来了一些希望，因此对 MJO-SSW 连接的研究对业务天气预报具有重要意义。该项目通过暑期实习为本科生和当地高中生提供支持，让他们接受 Python 编程和大气数据分析培训，从而产生更广泛的教育影响。该奖项还为两名研究生提供支持和培训，从而为该研究领域的未来劳动力提供支持。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进行评估，被认为值得支持。