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.

马登-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一种大型云量和降水模式，并在数周内缓慢向东传播。 该模式是一个东西向的偶极子，该区域的云量增加，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区域晴朗且降水减少。 MJO 被称为热带气象学的“圣杯”，因为迄今为止 50 年的研究尚未对其产生普遍接受的解释。MJO 有时被称为多尺度现象，因为它的雨半区最好被描述为对流包络，其中发生各种形式的对流聚集。 MJO 包络线内较小的对流扰动在多大程度上影响 MJO 的大尺度行为是一个悬而未决的问题。 这里进行的工作专门研究了 MJO 受天气开尔文波影响的程度，这种波扰动以赤道为中心，比 MJO 小，并通过其包络线从西向东传播。 PI 之前的工作表明，开尔文波的垂直倾斜在穿过对流包络线时会发生变化。 倾斜的变化可能会导致涡动量的垂直通量，从而有助于 MJO 向东推进。 开尔文波影响 MJO 的另一个机制涉及由于开尔文波对低位涡空气的平流而导致的上层隆起，这也可能有助于将 MJO 包络线向东移动。该项目结合使用统计技术和水分和动量预算检查来评估开尔文波对 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。 使用观测数据集完成分析后，将重复进行耦合模型比对项目 (CMIP) 的模拟。由于 MJO 对于远程天气预报的重要性，这项工作具有社会相关性。 MJO 影响世界各地的天气现象，包括亚洲的季风、墨西哥湾的飓风以及登陆美国西部的大气河流。 MJO 的缓慢传播意味着至少在原则上可以提前很好地预测其影响。 但 MJO 并没有在天气和气候模型中得到很好的捕捉，这里进行的工作可以直接为改进此类模型中的 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，作为 MJO 模拟改进的关键。 该项目支持两名研究生，从而培养该研究领域的未来劳动力。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。