A tropical stratopause precursor for sudden stratospheric warmings

Area of Science:

• Atmospheric Science
• Meteorology
• Climatology

Background:

• Sudden Stratospheric Warming (SSW) events are significant meteorological phenomena in the winter polar stratosphere.
• These events influence the entire atmospheric column, but their precursors are not fully understood.
• Previous research explored tropospheric forcing, stratospheric control, and external factors on SSW occurrence.

Purpose of the Study:

• To investigate a previously unexplored connection between the tropical upper stratosphere and the polar vortex.
• To identify early indicators for the occurrence of Sudden Stratospheric Warming (SSW) events.
• To understand the mechanism by which tropical stratopause conditions influence polar vortex disruption.

Main Methods:

• Utilized reanalysis datasets to analyze atmospheric conditions.
• Identified enhanced planetary wave driving around the tropical stratopause.
• Tracked the poleward progression of the zero-wind line as a key indicator.

Main Results:

• Enhanced planetary wave driving near the tropical stratopause and a poleward progression of the zero-wind line were identified as early indicators of SSW events.
• The poleward progression of the zero-wind line efficiently focuses planetary waves into the polar vortex, leading to its disruption.
• Approximately 70% of analyzed SSW events were preceded by enhanced tropical stratopause wave driving, suggesting it as a potential precursor.

Conclusions:

• Enhanced tropical stratopause wave driving serves as a potential precursor for Sudden Stratospheric Warming (SSW) events.
• The identified mechanism highlights the role of tropical upper stratosphere dynamics in polar vortex destabilization.
• A notable increase in SSW events preceded by enhanced tropical stratopause wave driving was observed after the year 2000.