Circulation Systems Flashcards
What are the three circulation systems that we are interested in?
- Mid-Latitude Depression
- Anticyclones
- Sea Breezes
What is a mid-latitude depression?
A structured low-pressure system that forms in the mid-latitudes normally with rain aligned along bands called fronts
What are the four stages to the lifecycle of a mid-latitude depression?
- Warm advection ahead of cold convection behind which leads to the development of an open wave depression (2 days on)
- Amplification - the depression matures and evacuation occurs aloft
- Becomes cut off
- Occluded depression leads to decay with cool air aloft - leads to heavy rain (5 days on)
5 Features of mid-latitude depression
- Heat Engines
- Sting Jets
- Storm Surges
- Low Pressure and Strong Winds
- Extra Tropical Hurricanes
What is an anticyclone?
An area of high pressure - the opposite to a depression
What is a sea breeze?
A light wind that blows from the sea to the land on a hot day, caused by the different properties of the land and sea surfaces
What is a sea breeze front?
The advancing edge of a sea breeze, where maritime air advances on the air over land
What does the Omega Block of the Jet Stream give?
Long periods of anticyclonic weather
What are the weather features associated with an anticyclone in the Summer?
Cloud free centre and fine, dry & low winds
What are the weather features associated with an anticyclone in the Winter?
Cold with frost and fog
What is the Anticylonic gloom?
Extensive sheets of Stratocumuls clouds giving fog and poor visibility
5 Features of Anticyclones
- Slow moving
- Little or no frontal movement
- Divergence and little density change (Barotropic)
- Descending air
- Temperature inversions
Give some information on a warm core anticyclone
Slow moving, they occupy large depths and a large geographical extent.
In sub tropical regions they are cloud free.
They allow net heat gain at the surface which allows ocean warming.
Gives a transfer of westerly momentum into mid latitudes which contributes to the formation of oceanic gyres
Give some information on a cold core anticyclone
They are mobile trough ridge systems with cold descending air between depressions and they reinforce anticyclones. They may be caused by extreme winter cooling
What happens when sea breezes reach land?
There is a rapid change in wind direction onshore which decreases temperatures and increases the dew point because of the oceanic moisture present, there may be a temperature difference of 2-3 Degrees C.
