Influence of QBO on stratospheric Kelvin and Mixed Rossby gravity waves in high-top CMIP5 models

[摘要] It is well established that quasi-biennial oscillation (QBO) has a substantial influence on Kelvin and mixed Rossby gravity (MRG) wave activity in the tropical lower stratosphere. In this study, we examined how QBO influences Kelvin and MRG wave activity in the lower stratosphere, based on nine high-top CMIP5 models. The results show that the Kelvin and MRG wave signals are stronger in the models with QBO, and relatively weaker in the models without QBO. The results are consistent with established theory, whereby upward-propagating Kelvin waves occurs more frequently during the easterly QBO phase, while upward-propagating MRG waves occurs during the westerly QBO phase. Without the QBO, the mean flow exhibits a near-zero easterly wind, which prevents the waves from propagating and penetrating into the stratosphere. Our analysis also shows that models with the QBO tend to have more robust signatures (in terms of amplitude and phase speed) of Kelvin and MRG waves.

[发布机构] Department of Geophysics and Meteorology, Bogor Agricultural University (IPB), Indonesia^1;Department of the Geophysical Sciences, University of Chicago, Chicago, United States^2

[效力级别] 生态环境科学

[关键词] Kelvin waves;Lower stratosphere;Mean flow;Phase speed;Quasi-biennial oscillation;Rossby-gravity wave;Wave activity;Wave signal