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-朱利安振荡(MJO)，这是一个在赤道印度洋形成并在一两个月内向东传播的云量和降雨量增加的地区。MJO具有全球影响，调节了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。近年来一个备受关注的问题是，MJO如何受到其上方平流层风的影响。在热带地区，平流层风由东向西或由东向西吹来，在大约两年的时间里改变了方向。风向逆转从顶部开始，以一种被称为准两年振荡(QBO)的级数下降。1980年以来的观测表明，在QBO的东风位相(平流层下部的风是从东来的)，MJO比西风位相更强，这种关系在北方冬季也是成立的。MJO在东风位相也具有较强的可预测性，因此QBO对MJO的调制具有亚季节预报的意义。文中探讨了两种可能性，第一种可能性是MJO被波能向上传播到平流层而受到抑制。这项工作是首席调查员(PI)早期研究的延伸，表明对流耦合赤道波的能量如何通过向上传播而损失。第二种可能性是QBO的风影响了MJO对流以上对流层顶层形成的卷云。卷云在捕获向外的长波辐射方面很有效，它们的辐射效应被认为是在MJO中发现的大片对流云的重要形成因素。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，或者间接地通过调制有利于卷云的上升运动来影响卷云。这项研究是通过建立一个理想化的理论模型来捕捉假设的影响，并通过使用最先进的大气模型-大气建模系统(SAM)进行模拟进行的。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显的影响，但调制的原因尚不清楚，而且很难评估它在多大程度上可以被用于更好的预测。此外，首席研究员担任本科生和研究生的导师，并参与拉蒙特开放之家等外展活动。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 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.