A sudden stratospheric warming (SSW) is a meteorological event where polar vortex winds in the Northern Hemisphere abruptly slow or reverse, accompanied by a rise in stratospheric temperature. SSWs are classified as major, minor, or final. Major SSWs completely disrupt the polar vortex through wind reversal. Minor SSWs slow winds but do not reverse them. A final SSW occurs on the transition from winter to summer winds and is the last warming of the winter season.

1. A sudden stratospheric warming (SSW) is an event where the polar vortex of
westerly (eastwards) winds in the Northern winter hemisphere abruptly slows down or even
reverses direction, accompanied by a rise of stratospheric temperature by several tens of kelvins.
This is considered to be the most dramatic meteorological event in the stratosphere. SSW is
classified into three categories: major minor and final Major : These occur when the westerly
winds at 60N and 10hPa (geopotential height) reverse, i.e. become easterly (westwards). A
complete disruption of the polar vortex is observed and the vortex will either be split into
daughter vortices, or displaced from its normal location over the pole. According to the World
Meteorological Organization's Commission for Atmospheric Sciences a stratospheric warming
can be said to be major if 10 mb or below the latitudinal mean temperature increases poleward
from 60 degree latitude and an associated circulation reversal is observed (that is, the prevailing
mean westerly winds poleward of 60 latitude are succeeded by mean easterlies in the same area).
Minor : Minor warmings are similar to major warmings however they are less dramatic, the
westerly (eastward) winds are slowed, however do not reverse. Therefore a breakdown of the
vortex is never observed. A stratospheric warming is called minor if a significant temperature
increase is observed (that is, at least 25 degrees in a period of week or less) at any stratospheric
level in any area of winter time hemisphere. The polar vortex is not broken down and the wind
reversal from westerly (eastwards) to easterly (westwards) is less extensive. Final : The radiative
cycle in the stratosphere means that during winter the mean flow is westerly (eastward) and
during summer it is easterly (westward). A final warming occurs on this transition, so that the
polar vortex winds change direction for the warming, however do not change back until the
following winter. This is because the stratosphere has entered the summer easterly (westward)
phase. It is final because another warming cannot occur over the summer, so it is the final
warming of the current winter.
Solution
A sudden stratospheric warming (SSW) is an event where the polar vortex of
westerly (eastwards) winds in the Northern winter hemisphere abruptly slows down or even
reverses direction, accompanied by a rise of stratospheric temperature by several tens of kelvins.
This is considered to be the most dramatic meteorological event in the stratosphere. SSW is
classified into three categories: major minor and final Major : These occur when the westerly
winds at 60N and 10hPa (geopotential height) reverse, i.e. become easterly (westwards). A
complete disruption of the polar vortex is observed and the vortex will either be split into
daughter vortices, or displaced from its normal location over the pole. According to the World
Meteorological Organization's Commission for Atmospheric Sciences a stratospheric warming
can be said to be major if 10 mb or below the latitudinal mean temperature increases poleward

2. from 60 degree latitude and an associated circulation reversal is observed (that is, the prevailing
mean westerly winds poleward of 60 latitude are succeeded by mean easterlies in the same area).
Minor : Minor warmings are similar to major warmings however they are less dramatic, the
westerly (eastward) winds are slowed, however do not reverse. Therefore a breakdown of the
vortex is never observed. A stratospheric warming is called minor if a significant temperature
increase is observed (that is, at least 25 degrees in a period of week or less) at any stratospheric
level in any area of winter time hemisphere. The polar vortex is not broken down and the wind
reversal from westerly (eastwards) to easterly (westwards) is less extensive. Final : The radiative
cycle in the stratosphere means that during winter the mean flow is westerly (eastward) and
during summer it is easterly (westward). A final warming occurs on this transition, so that the
polar vortex winds change direction for the warming, however do not change back until the
following winter. This is because the stratosphere has entered the summer easterly (westward)
phase. It is final because another warming cannot occur over the summer, so it is the final
warming of the current winter.