[A-AS10] Stratosphere-troposphere Processes And their Role in Climate

[AAS10-11] Influence of the stratospheric QBO on seasonal migration of the convective center across
the Maritime Continent

*Kunihiko Kodera¹, Tomoe Nasuno², Seok-Woo Son³, Nawo Eguchi⁴, Yayoi Harada¹ (1.Meteorological Research Institute, 2.JAMSTEC, 3.Seoul National University, 4.Research Institute for Applied Mechanics, Kyushu University)

Keywords:QBO, Convection, Maritime Continent, Monsoon

Modulation of tropical convection by the stratospheric quasi-biennial oscillation (QBO) during the boreal winter has become evident in recent studies. In this study, we show that the QBO affects the seasonal migration of the tropical convection from the equatorial Indian Ocean to the Western Pacific: large-scale convection over the Maritime Continent (MC) and western Pacific strengthens and moves eastward more effectively during easterly QBO (QBO–E) boreal winters. This relationship, which is consistent with an enhanced Madden–Julian Oscillation (MJO) in the QBO–E, is likely due to the strengthened low temperature anomalies in the tropical tropopause layer (TTL) in the QBO–E. The monsoonal active convection over the Sumatra–Borneo region in December produces Kelvin wave-like low temperature anomalies in the TTL over the eastern MC. These temperature anomalies strengthen when the lower stratospheric wind is easterly, providing favorable conditions for deep convection to develop over the eastern MC. Thus, the seasonal march of deep convection over the MC is aided by the Kelvin wave-like response in the TTL under the QBO–E. The applicability of this process to the QBO modulation of the MJO crossing the MC is also discussed.