Polar Atmosphere Phenomena
: Focusing on the Polar Vortex
Mid-latitude Extreme Weather
2. Contours and temperature anomalies in the stratosphere and troposphere during 2018 SSW
The graph illustrates that immediately following an SSW event (from day 0 to +7), the polar stratosphere experiences a powerful warming and a significant anticyclonic anomaly at high altitudes.
This indicates a rapid temperature increase in the upper polar region, strongly suggesting that the polar vortex has weakened and been disrupted.
Around 7 to 21 days after the SSW event, a different phenomenon is observed: tropospheric temperatures over Europe drop significantly below normal. This is a clear manifestation of the "Beast
from the East" cold wave that struck the region during this period.
The information suggests a strong link between the 2018 SSW and this cold wave. The mechanism works as follows:
i. Polar Vortex Disturbance: Right after the SSW, the polar vortex in the polar stratosphere weakens and becomes disturbed.
ii. Downward Propagation: This disturbance propagates downward from the stratosphere to the troposphere over the following one to two weeks.
iii. Jet Stream Disruption: The downward-propagating changes disrupt the jet stream, a fast-flowing air current that typically confines cold Arctic air to the polar region.
iv. Cold Air Outbreak: The disrupted jet stream allows the frigid Arctic air to spill southward into Europe, causing the unusually low temperatures on the ground.
This process demonstrates how stratospheric events can have a significant and delayed impact on
weather patterns in the troposphere, leading to extreme cold events like the "Beast from the East."
1. Northen Hemisphere Polar vortex area 2020-2021
The provided graph illustrates the polar vortex area during the 2021 Texas freeze. The red line represents the actual polar vortex area from 2020-2021, while the yellow line shows the historical average.
The graph clearly shows that from mid-January to mid-February, the polar vortex area sharply decreased, dropping to less than 10% of historical data. This period coincides with the peak of the Texas freeze in mid-February 2021.
This data indicates that the polar vortex, which typically confines frigid Arctic air to the polar region, was too small and weak to perform its function properly. As a result, the cold air was able to spill southward, leading to the severe cold wave that impacted Texas.
