November 4, 2020 - 3:00 pm
November 4, 2020 - 4:00 pm
CategoriesWeather and Climate Systems
Weather and Climate Systems Seminar
Assessment of Stratospheric Waves Activity Associated with the MJO During QBO Phases
Wednesday, November 4th
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Madden-Julian Oscillation (MJO) and Quasi-Biennial Oscillation (QBO) are known to provide sources of sub-seasonal to seasonal predictability, yet their dynamics and interactions are not fully understood. The MJO is a planetary-scale variability of the tropical atmosphere which is characterized by eastward-moving pulses of anomalous cloudiness and rainfall near the equator on the intra-seasonal timescale. On the other hand, the QBO is a tropical stratospheric phenomenon of quasi-periodic oscillation of equatorial zonal wind of easterlies and westerlies with a mean period of 28 to 29 months. Many recent studies have found that the MJO amplitude tends to be higher during the easterly phase of the QBO while MJO amplitude tends to be weaker during the westerly phase of the QBO. It is often believed that this relationship arises through the impacts of the QBO on the MJO activities, but the impacts of the MJO deep convection on the evolution of the QBO have not been examined in detail. Vertical momentum fluxes by stratospheric equatorial Kelvin and Rossby-gravity waves generated by tropical deep convection are known to play important roles for the dynamics of the QBO, which can be modulated by the MJO convective activity. Therefore, the main objective of this research is to examine potential changes in the stratospheric wave activity associated with the MJO and its potential impacts on the QBO using reanalysis data and wavenumber-frequency spectral analysis. More specifically, we will assess how the stratospheric wave activity is modulated by the MJO convection during the different phases of the QBO.