How Atmospheric Synoptic Kelvin Waves Influenced the Propagation of the Madden-Julian Oscillation (MJO)

大气天气开尔文波如何影响马登-朱利安振荡 (MJO) 的传播

• 批准号: 2103624
• 负责人: Paul Roundy
• 金额: $ 48.85万
• 依托单位: SUNY at Albany
• 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: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2103624&HistoricalAwards=false
• 关键词: How; Atmospheric; Synoptic; Kelvin; Waves

The Madden-Julian Oscillation (MJO) is a large pattern of cloudiness and precipitation that forms over the equatorial Indian Ocean and the adjacent west Pacific and propagates slowly eastward over several weeks. The pattern is an east-west dipole with a region of enhanced cloudiness and rainfall big enough to cover much of the tropical Indian Ocean, accompanied by an equally large region of clear skies and reduced precipitation to the east. The MJO has been called the "holy grail" of tropical meteorology, as 50 years of research to date has not produced a generally accepted explanation for it.The MJO is sometimes called a multiscale phenomenon since its rainy half is best described as an envelope of convection in which various forms of convective aggregation occur. The extent to which the smaller convective disturbances within the MJO envelope affect the large-scale behavior of the MJO is an open question. Work conducted here looks specifically at the extent to which the MJO is influenced by synoptic Kelvin waves, wave disturbances centered on the equator which are smaller than the MJO and propagate through its envelope from west to east. Previous work by the PI shows that the vertical tilt of the Kelvin waves is altered as they move through the convective envelope. The change in tilt may lead to a vertical flux of eddy momentum that contributes to the eastward advance of the MJO. A further mechanism through which Kelvin waves can affect the MJO involves upper-level ridging due to the advection of low potential vorticity air by the Kelvin waves, which could also help move the MJO envelope eastward.The project uses a combination of statistical techniques combined with examination of the moisture and momentum budgets to assess Kelvin wave impacts on the MJO. Datasets to be used include reanalysis products and satellite-based estimates of convective clouds and rainfall. Once the analysis is completed using observational datasets it is repeated for simulations from the Coupled Model Intercomparison Project (CMIP).The work has societal relevance due to the importance of the MJO for long-range weather prediction. The MJO influences weather phenomena around the world including the monsoons of Asia, hurricanes in the Gulf of Mexico, and atmospheric rivers making landfall in the western US. The slow propagation of the MJO means that its effects can, at least in principle, be anticipated well in advance. But the MJO is not well captured in weather and climate models, and work conducted here can directly inform efforts to improve MJO simulation in such models. In particular the work may show the need for better simulation and initialization of Kelvin waves as a key to MJO simulation improvement. The project supports two graduate students, thereby developing 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.

麦登-朱利安涛动（MJO）是在赤道印度洋和邻近的西太平洋上空形成的大型云和降水模式，并在数周内缓慢向东传播。这种模式是东西向的偶极子，云量增加，降雨量大到足以覆盖热带印度洋的大部分地区，同时东部也有同样大的晴空，降水减少。MJO被称为热带气象学的“圣杯”，因为迄今为止50年的研究还没有产生一个普遍接受的解释。MJO有时被称为多尺度现象，因为它的多雨部分最好描述为对流包络层，其中发生各种形式的对流聚集。MJO包络内较小的对流扰动对MJO大尺度行为的影响程度是一个悬而未决的问题。这里进行的工作特别关注MJO受天气开尔文波影响的程度，开尔文波以赤道为中心，比MJO小，并从西向东通过其包络传播。PI先前的工作表明，开尔文波在穿过对流包络层时，其垂直倾斜度会发生改变。倾斜的变化可能导致涡旋动量的垂直通量，有助于MJO向东推进。开尔文波影响MJO的另一个机制是，由于开尔文波对低位势涡度空气的平流，导致上层脊化，这也有助于MJO包层向东移动。该项目将统计技术与水分和动量预算相结合，以评估开尔文波对MJO的影响。将使用的数据集包括再分析产品和基于卫星的对流云和降雨估计。一旦使用观测数据集完成分析，就会在耦合模式比对项目（CMIP）的模拟中重复分析。由于MJO对长期天气预报的重要性，这项工作具有社会意义。MJO影响着世界各地的天气现象，包括亚洲的季风、墨西哥湾的飓风和在美国西部登陆的大气河流。MJO的缓慢传播意味着，至少在原则上，可以很好地提前预测到它的影响。但是天气和气候模式并没有很好地捕捉到MJO，这里进行的工作可以直接为改进这些模式中的MJO模拟提供信息。特别是，这项工作可能表明需要更好地模拟和初始化开尔文波，这是改进MJO模拟的关键。该项目支持两名研究生，从而在该研究领域发展未来的劳动力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。