Collaborative Research: The Quasi-Biennial Oscillation and Madden-Julian Oscillation (QBO-MJO) Connection: Positive Feedbacks from Extratropical Wave Forcing

在30到60天的时间尺度上，马登-朱利安涛动(MJO)主导着对流层热带气候的变化。在冬季，与MJO相关的对流风暴激发了行星级的波动扰动，影响了美国的天气，扰乱了平流层。准两年振荡(QBO)控制着热带低平流层的变化，并指导着行星尺度的波动如何穿透到平流层。观测结果表明，QBO对MJO模式的发生和东移具有一定的调控作用。然而，这种QBO-MJO关系在现有的全球气候模型(GCM)中并不明显。这项研究试图更好地理解这种关系，并解决为什么它在模型中仍然难以捉摸。对QBO-MJO联系的新认识可能会推进对流层和平流层之间耦合的现有知识，扩大天气预报的预报范围，并指导新的GCM改进。这项工作将支持和培训一名全日制研究生，并利用国家大气研究中心全大气社区气候模式(即WACCM6-110L)，这是一个模拟现实MJO和QBO的GCM。研究目标是评估几种可能对观测到的QBO影响MJO有显著贡献的正反馈机制。一个需要评估的关键机制是，由于热带外Rossby波的吸收和消散，在QBO(即QBOE)的东相期间，热带上升流和热带对流层/平流层下部(UTLS)区域的不稳定增加。这些波动同时受到MJO和QBO的影响。这五项任务是：(1)量化QBOE与QBO西风位相(即QBOW)冬季UTLS温度和静力稳定度之间的差异作为经纬度的函数；(2)确定MJO诱发的温带Rossby波列的强度和由此产生的上行波活动通量作为MJO强度和QBO位相的函数；(3)诊断QBOE期间波列和波活动通量相对于QBOW的强度；(4)评估WACCM6-110L是否能够模拟观测到的QBO-MJO连接以及观测到的UTLS温度、副热带急流结构和波动活动通量中的QBO位相差异；以及(5)对WACCM6-110L进行新的实验，以确定需要的模式改进。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Madden-Julian Oscillation (MJO) dominates the tropical climate variability in the troposphere on the 30-to-60-day timescale. During the winter, convective storms associated with the MJO excite planetary-scale wave disturbances that impact the U.S. weather and perturb the stratosphere. The Quasi-Biennial Oscillation (QBO) governs the variability in the tropical lower stratosphere and guides how planetary-scale wave disturbances penetrate into the stratosphere. Observations reveal that the QBO can modulate the occurrence and eastward migration of the MJO pattern. However, this QBO-MJO relationship is not evident in existing global climate models (GCMs). This research seeks to better understand this relationship and address why it remains elusive in models. New insight about the QBO-MJO connection may advance current knowledge of the coupling between the troposphere and stratosphere, extend the forecast range of weather prediction, and guide new GCM improvement. The work will support and train a full-time graduate student and leverage the National Center for Atmospheric Research Whole Atmosphere Community Climate Model (namely, WACCM6-110L), a GCM that simulates realistic MJO and QBO.The research objective is to assess several positive feedback mechanisms that may contribute significantly to the observed QBO influence on the MJO. A key mechanism to assess involves the increased tropical upwelling and destabilization of the tropical upper troposphere/lower stratosphere (UTLS) region during the easterly phase of the QBO (i.e., QBOE) due to the absorption and dissipation of extratropical Rossby waves. These waves are influenced by both the MJO and the QBO. Five tasks are: (1) To quantify the observed differences between QBOE and the westerly phase of the QBO (i.e., QBOW) of the wintertime UTLS temperature and static stability as a function of latitude and longitude; (2) To determine the strength of the MJO-induced extratropical Rossby wave train and resulting upward wave activity flux as a function of MJO strength and QBO phase; (3) To diagnose the strength of the wave train and wave activity flux during the QBOE relative to QBOW; (4) To evaluate if WACCM6-110L can simulate the observed QBO-MJO connection and the observed QBO phase differences in UTLS temperature, subtropical jet structure, and wave activity flux; and (5) To perform new experiments on WACCM6-110L to identify needed model improvements.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.