Influences of El Nino-Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO) on the Stratosphere

传统观点认为，低层大气主要通过中高纬度对流层产生的行星波影响平流层。然而，最近有证据表明，热带对流层的主要变率模式，即厄尔尼诺-南方涛动（ENSO）和马登-朱利安涛动（MJO），影响着热带和温带平流层。对于这种影响，人们提出了多种途径。在本项目中，将利用观测数据和对流层-平流层全球气候模式（GCMs）的输出来探索这些途径。观测将包括欧洲中期天气预报中心（ECMWF）对气象场和臭氧的ERA-40分析，以及对对流特征的发射长波辐射的卫星观测。Weare和他的合作者将建立关键ENSO和MJO模式的指数。统计技术将用于确定平流层变率的主要模式。他们将利用扩展的奇异值分解（SVD）方法，结合多变量和时间滞后数据，描述受MJO和ENSO调制的热带对流与平流层气象和平流层臭氧分布之间的三维关系。根据这些探索性分析中出现的关系，他们将对热带对平流层影响的具体建议途径开发诊断测试。根据平流层变率模拟的质量以及ENSO和MJO的模式表示，将从一个或多个模式中选择GCM输出。本文将分析这种或这些gcm中的对流层-平流层耦合，以便找出它们对这种耦合模拟中的不足之处，目的是提出改进模式的建议，使对流层-平流层耦合模式与观测结果更加一致。本项目的更广泛影响在于验证广泛使用的平流层数据集，提高我们对影响平流层臭氧趋势的过程的理解，并且在对流层-平流层耦合是气候变化的一个重要方面的情况下，改进对未来气候的预测。将培训两名研究生。

The conventional view has been that the lower atmosphere influences the stratosphere primarily through planetary waves that emerge from the troposphere in middle and high latitudes. Recently, however, evidence has emerged that the leading modes of variability of the tropical troposphere, the El Nino-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO), influence the tropical and extratropical stratosphere. Multiple pathways have been proposed for such influences. In this project these pathways will be explored using observational data and the output from troposphere-stratosphere global climate models (GCMs). Observations will comprise the ERA-40 analyses of meteorological fields and ozone from the European Center for Medium Range Weather Forecasting (ECMWF) and satellite observations of outgoing long-wave radiation to characterize convection.Weare and his collaborators will establish indices of the key ENSO and MJO modes. Statistical techniques will be used to determine the dominant patterns of variability in the stratosphere. Using an extension of the singular value decomposition (SVD) method that incorporates multiple variables and data at temporal lags, they will describe the three dimensional relationships between tropical convection, as it is modulated by the MJO and ENSO, and the meteorology of the stratosphere and the distribution of stratospheric ozone. Based on the relationships that appear in these exploratory analyses, they will develop diagnostic tests of specific proposed pathways for tropical influences on the stratosphere.GCM output will be selected from one or more models, based on the quality of the simulations of stratospheric variability and the model representations of ENSO and the MJO. The troposphere-stratosphere coupling in this, or these, GCMs will be analyzed, in order to identify deficiencies in their simulation(s) of this coupling, with the goal of suggesting model improvements that could yield model troposphere-stratosphere coupling that is more consistent with observations.Broader impacts of this project are in validating widely used stratospheric data sets, improving our understanding of the processes that influence trends in stratospheric ozone, and, to the extent that troposphere-stratosphere coupling is an important aspect of climate change, improving projections of future climate. Two graduate students will be trained.