AGS-PRF: A Theoretical Framework to Investigate the Madden Julian Oscillation-Quasi Biennial Oscillation (MJO-QBO) Relationship--Upward Wave Radiation and Thin-Cirrus Feedbacks

AGS-PRF：研究马登朱利安振荡-准两年振荡（MJO-QBO）关系的理论框架——上行波辐射和薄卷云反馈

• 批准号: 2201441
• 负责人: Jonathan Lin
• 金额: $ 19万
• 依托单位: Lin, Jonathan
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2201441&HistoricalAwards=false
• 关键词: AGS; PRF; Theoretical; Framework; Investigate

The largest weather pattern in the world is the Madden-Julian Oscillation (MJO), an area of enhanced cloudiness and rainfall that forms over the equatorial Indian Ocean and propagates eastward over the course of a month or two. The MJO has worldwide impacts, modulating the number of hurricanes that form in the Gulf of Mexico, the rainy seasons of Asia, Australia, Africa, and the Americas, and the formation of the atmospheric rivers that cause flooding along the US West Coast. One issue that has gained prominence in recent years is how the MJO is influenced by the winds in the stratosphere above it. In the tropics the stratospheric wind blow from east to west or vice versa, changing direction over the course of about two years. The wind reversal starts at the top and descends in a progression known as the Quasi-Biennial Oscillation (QBO). Observations since 1980 show that the MJO is more robust in the easterly phase of the QBO (when the wind in the lower stratosphere is from the east) than in the westerly phase, a relationship which holds during the northern winter. The MJO is also more predictable in the easterly phase, thus the modulation of the MJO by the QBO has implications for subseasonal prediction.Work performed here seeks to understand why the MJO is sensitive to the phase of the QBO. Two possibilities are explored, the first being that the MJO is damped by the upward propagation of wave energy into the stratosphere. The work is an extension of earlier research by the Principal Investigator (PI) showing how the energy of convectively coupled equatorial waves can be lost through upward propagation. The second possibility is that the wind of the QBO influences the cirrus clouds that form at the tropopause level above convection in the MJO. Cirrus clouds are effective at trapping outgoing longwave radiation, and their radiative effect is thought to be important for creating the large areas of convective clouds found in the MJO. The QBO could affect the cirrus clouds either directly, as the QBO wind moves the clouds in one direction or the other, or indirectly through modulating the rising motions that favor cirrus clouds. The research is conducted through the development of an idealized theoretical model that captures the hypothesized effects and through simulations using a state-of-the art atmospheric model, the System for Atmospheric Modeling (SAM).The work has societal value due to the worldwide weather and climate effects of the MJO. The modulation of the MJO by the QBO has clear implications for subseasonal prediction, as noted above, but the reasons for the modulation are not known and the extent to which it can be harnessed for better predictions is difficult to assess. In addition, the Principal Investigator serves as a mentor to undergraduate and graduate students and participates in outreach activities such as the Lamont Open House.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.

世界上最大的天气模式是Madden-julian振荡（MJO），这是赤道印度洋上形成的云彩和降雨增强的区域，并在一两个月的时间内向东传播。 MJO在墨西哥湾，亚洲，澳大利亚，非洲和美洲的飓风数量以及在美国西海岸造成洪水的大气河流的形成。近年来，一个越来越重要的问题是，MJO如何受到其上方平流层中的风的影响。 在热带地区，平流层风从东到西面，反之亦然，在大约两年的过程中改变了方向。 风反转从顶部开始，并以称为准生物振荡（QBO）的进程下降。 自1980年以来的观察结果表明，MJO在QBO的东方阶段（下层平流层中的风）比西风相比在北部冬季建立的关系更强大。 MJO在东方阶段也更容易预测，因此QBO对MJO的调节对亚季节的预测有影响。此处执行的工作试图理解为什么MJO对QBO的阶段敏感。 探索了两种可能性，首先是通过波能向平流层传播的MJO受到抑制。这项工作是首席研究者（PI）对早期研究的扩展，该研究表明如何通过向上的传播浪费对流耦合赤道波的能量。 第二种可能性是，QBO的风会影响MJO中对流高于对流的对流层面上形成的卷云。 卷云在捕获外向的长波辐射方面有效，其辐射效应被认为对于创建MJO中发现的对流云很重要。 QBO可以直接影响卷云，因为QBO风向一个方向或另一个方向移动云，或者通过调节有利于Cirrus Clouds的上升运动而间接地移动云。 这项研究是通过开发理想化的理论模型进行的，该模型捕获了假设的效果，并通过使用最先进的大气模型，大气建模系统（SAM）进行模拟。由于全球的天气和MJO的气候效应，工作具有社会价值。如上所述，通过QBO对MJO的调节对亚季节预测具有明显的影响，但是调制的原因尚不清楚，并且难以评估它可以利用它以获得更好的预测的程度。 此外，首席调查员还担任本科和研究生的导师，并参加了诸如Lamont Open House之类的外展活动。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准通过评估来获得支持的。

项目成果

Stratospheric Modulation of the MJO through Cirrus Cloud Feedbacks

• DOI: 10.1175/jas-d-22-0083.1
• 发表时间: 2022-04
• 期刊: Journal of the Atmospheric Sciences
• 影响因子: 3.1
• 作者: Jonathan Lin;K. Emanuel