Classification of stratospheric extreme events according to their downward propagation to the troposphere

Anomalous strong and weak stratospheric polar vortex events are detected from daily time series of the polar cap averaged (60°–90°N) geopotential height anomaly. The method is applied to chemistry-climate model data (E39CA and WACCM3.5) and reanalyses data (ERA40).

The analyses show that in about 80% of all events no significant tropospheric response can be detected. The stratospheric perturbation of both weak and strong events with a significant tropospheric response persists significantly longer throughout the stratosphere compared to the events without a tropospheric response. The strength of the stratospheric perturbation determines the strength of the tropospheric response only to a small degree.