Hindcast AGCM Experiments on the Predictability of Stratospheric Sudden Warming

Abstract

High sensitivity to the initial condition of the prediction for a stratospheric sudden warming (SSW) event occurring in December 2001 reported by Mukougawa, Sakai, and Hirooka (2005) is confirmed by conducting a series of hindcast experiments using an atmospheric general circulation model (MRI/JMA-GCM). Similar precursory circulation anomaly in the troposphere for the occurrence of the SSW is also obtained through a regression analysis on the GCM experiments. Furthermore, it is revealed that the response of stratospheric circulation to the magnitude of the precursory anomaly is nonlinear, which suggests the existence of a threshold magnitude of the precursory anomaly for the occurrence of the SSW. Detailed investigation on the precursory event will enable us to reveal the dynamical relationship between tropospheric circulation anomaly and the subsequent SSW.