Interannual variation of seasonal-mean tropical convection over the Indo-Pacific region is primarily controlled by El Niño-Southern Oscillation (ENSO). For example, during El Niño winters, seasonal-mean convection around the Maritime Continent becomes weaker than normal, while that over the central to eastern Pacific is strengthened. Similarly, subseasonal convective activity, which is associated with the Madden-Julian oscillation (MJO), is influenced by ENSO. The MJO activity tends to extend farther eastward to the date line during El Niño winters and contract toward the western Pacific during La Niña winters. However, the overall level of MJO activity across the Maritime Continent does not change much in response to the ENSO. It is shown that the boreal winter MJO amplitude is closely linked with the stratospheric quasi-biennial oscillation (QBO) rather than with ENSO. The MJO activity around the Maritime Continent becomes stronger and more organized during the easterly QBO winters. The QBO-related MJO change explains up to 40% of interannual variation of the boreal winter MJO amplitude. This result suggests that variability of the MJO and the related tropical-extratropical teleconnections can be better understood and predicted by taking not only the tropospheric circulation but also the stratospheric mean state into account. The seasonality of the QBO-MJO link and the possible mechanism are also discussed.
Bibliographical noteFunding Information:
We thank the ECMWF, NOAA, UCAR, and NASA for providing us with the reanalysis data and various satellite datasets.Wealso thank Sang-Woo Kim for processing CALIOP data, and Daehyun Kim, Fei Liu, and Kyong-Hwan Seo for helpful discussion. This work is supported by the Korea Meteorological Administration Research and Development Program under Grant KMIPA 2015-2094 and by the National Research Foundation of Korea under Grant NRF-2016R1C1B2006310.
© 2017 American Meteorological Society.
- Interannual variability
- Madden-Julian oscillation
- Quasibiennial oscillation
- Stratosphere-troposphere coupling