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

[AAS06-07] Do sudden stratospheric warmings boost convective activity in the tropics?

★Invited Papers

*Kohei Yoshida¹, Ryo Mizuta¹ (1.Meteorological Research Institute)

Keywords:Sudden stratospheric warming, Stratosphere-Troposphere coupling in the tropics, High-resolution large-ensemble simulations

Influence of stratospheric meridional circulation changes related to sudden stratospheric warmings (SSW) on the tropical troposphere have been examined in many previous studies. However, due to small sample size of SSWs and large internal variability in the tropical troposphere, influence of the SSW on the tropical troposphere is still uncertain. We examine impact of the stratospheric circulation changes related to SSW on the tropical troposphere using 5,000-year scale ensemble simulations with a 60 km horizontal resolution global atmospheric model MRI-AGCM3.2. More than 1,000 of SSW-like circulation change events are extracted thanks to the large ensemble simulations. A composite analysis of the SSW-like events shows significant stratospheric upwelling and cooling in the tropics. Synchronized with the upwelling, statistically robust tropospheric signals such as enhanced convective activity including tropical cyclone are found. Although the mean tropospheric signals tend to be small, relative probability of their extreme events significantly increases. Influence of tropospheric waves to tropical troposphere is also discussed.