Northern empishere: 100 hPa temperature (~ 16 km altitude)
The observation of the geopotentials at 100 hPa is important to evaluate the state
of the polar vortex and predict possible split of the same, which can lead to cold air
irruptions towards the middle latitudes.
The split of the polar vortex is often the consequence of sudden increases in temperatures in the
stratosphere (sudden stratospheric warming, SSW) which in their most intense
form (major stratwarming) can reach variations of 50/60 °C within a week.
For this reason, analysis and forecast of temperature at 100 hPa, corresponding
to an altitude of about 16 km, is important.
It should be emphasized that a major warming does not always correspond to a weakening of the polar
vortex. At the same time, mid-latitude cold air outbursts are not always the result of stratwarming,
but can be caused by a weak
El Niño or by solar
activity, both of which favor a weakening of the tropospheric polar vortex.
We also recommend consulting our page dedicated to the stratosphere
analysis, with diagrams useful for identifying stratwarming, the one dedicated to
stratosphere temperatures at North Pole, and finally the one dedicated to
temperatures and geopotentials at 10 hPa.
Southern emisphere: 100 hPa temperature (~ 16 km altitude)
As before, temperatures and geopotentials in the southern hemisphere are shown here.