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

世界上最大的天气模式是马登-朱利安涛动（MJO），这是一个云量和降雨增强的区域，在赤道印度洋上空形成，并在一两个月的时间里向东传播。MJO具有世界范围的影响，调节墨西哥湾形成的飓风数量，亚洲、澳大利亚、非洲和美洲的雨季，以及导致美国西海岸洪水的大气河流的形成。近年来一个引人注目的问题是MJO是如何受到其上方平流层风的影响的。在热带地区，平流层的风从东向西吹，反之亦然，在大约两年的时间里改变方向。风反转从顶部开始，以准两年一次振荡（QBO）的方式下降。1980年以来的观测表明，MJO在QBO的东风阶段（当平流层低层的风来自东方时）比西风阶段更为强劲，这种关系在北方冬季期间保持不变。MJO在东风阶段也更容易预测，因此QBO对MJO的调制对亚季节预报有影响。这里执行的工作旨在理解为什么MJO对QBO的阶段敏感。研究人员探索了两种可能性，第一种可能性是MJO受到波能向上传播到平流层的阻尼。这项工作是对早期首席研究员（PI）研究的延伸，该研究表明对流耦合的赤道波的能量如何通过向上传播而损失。第二种可能是QBO的风影响了在MJO对流上方对流层顶形成的卷云。卷云能有效地捕获传出的长波辐射，它们的辐射效应被认为是在MJO中形成大面积对流云的重要因素。QBO可以直接影响卷云，因为QBO风将云向一个方向或另一个方向移动，或者通过调制有利于卷云的上升运动间接影响。这项研究是通过开发一个理想化的理论模型来进行的，该模型可以捕捉到假设的影响，并通过使用最先进的大气模型——大气模拟系统（SAM）进行模拟。由于MJO对全球天气和气候的影响，这项工作具有社会价值。如上所述，QBO对MJO的调制对亚季节预测有明确的影响，但调制的原因尚不清楚，而且很难评估利用它进行更好预测的程度。此外，首席研究员还担任本科生和研究生的导师，并参加拉蒙特开放日等外展活动。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。

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.