Chapter 5 - Pressure Systems Flashcards
How does a subsidence inversion form?
In a high pressure system when the descending air warms adiabatically it gets warmer than the cold air which is already below it.
What is meant by a depression?
An area of low pressure.
What is mean by an anticyclone?
An area of high pressure.
What is the Buys Ballots law?
With the wind behind you in the northern hemisphere, the low pressure system is to your left. (also works for temperature).
Why are wind speeds around a high lower than around a low?
Due to the earths spin opposing the rotation around a high.
What are the convergence and divergence characteristics of an anticyclone?
the air converges at altitude and diverges at the surface.
How wide is a small scale low?
1 - 20 miles
Where do small scale lows occur?
Over land, resulting from thermal lows but may also occur on the leeward side of hills
Where do large scale lows occur?
Through surface heating or warm air intruding into a cold air mass.
Also at polar front where large depressions can form.
What are the convergence and divergence characteristics of a depression?
Air converges at the surface and diverges at altitude.
How can anticyclones form?
By cooling of air at the surface causing air to sink.
What kind of weather is associated with an anticyclone?
They are slow moving, have generally light winds and weather usually lacks precipitation.
Where do warm anticyclones occur and what are they often called?
They are found around 30deg N/S.
Due to the hadley and ferrel cell interaction.
Azores highs
Where do cold anticyclones occur?
From cold surfaces or frontal waves, usually occuring in Siberia and Canada in winter.
Also over the poles.
Where do warm lows form?
At the equator or large areas of warm sea.
they usually result in TRSs
