[A-AS06] Atmospheric (Stratosphere-troposphere) Processes And their Role in Climate

[AAS06-P04] What type of QBO-related variation induces polar vortex and surface changes?

*Kohei Yoshida¹ (1.Meteorological Research Institute)

Keywords:Stratosphere-troposphere coupling, Climate modeling, QBO

Most of QBO driving climate models can not reproduce observed QBO-polar vortex relationship (Holton-Tan) enough. To understand whether observed QBO amplitude and timeseries induce stratospheric polar vortex (SPV) variation as observed, QBOi suggested QBOi2 nudging experiment protocol, which zonal mean zonal wind in QBO region is relaxed to observed one. However, at least Meteorological Research Institute earth system model ver. 2.0 (MRI-ESM2.0) can not reproduce the amplitude QBO synchronized SPV variation enough. To understand which type of QBO related variations is important for QBO synchronized SPV variations, we performed additional experiments which enlarges nudging regions (e.g. wider latitude band) using MRI-ESM2.0. Wider nudging latitude case and higher nudging top lid case tend to increase amplitude of QBO synchronized polar vortex variation. However the changes depend on the calendar month and do not occur whole winter season, which may be affected planetary-scale wave activity and seasonal change of polar vortex climatology. More discussion would be done in the workshop.