Chapter 17 - Air Masses Flashcards
What 3 questions should you ask when thinking about air mass weather?
Where has it come from? What are it’s conditions? (eg. stable? cold?) What happened en-route? (eg. did it pick up water?)
Where do most air masses originate from?
Areas of high pressure due to slow moving.
What temperature/latitude classifications are used for air masses?
Tropical (T) - for air masses originating from latitudes up to around 40deg
Polar (P) - originating from between 30 - 70 deg latitude
Arctic (A) - orginating from high latitudes near the poles.
What are the airmass classifications based on humidity?
Maritime (m) - based on airmasses coming from seas
Continental (c) - based on air masses coming from land.
What air masses affect the UK?
South westerly mT
Northerly mA
North westerly mP
Southerly cT
Easterly cP (Summer)
Easterly cP (Winter)
Returning mP
What kind of weather does the south westerly mT air mass bring to the UK?
Warm moist air that cools over colder land causing stable atmosphere.
Turbulence in the friction laye cause turbulent mixing and an inversion which brings low cloud/advection fog.
Usually overcast and mild
What kind of weather does the northerly mA air mass bring to the UK?
Cold moist air moving over warmer land that heats it from below causing an untable atmosphere.
Convection then causes Cu clouds with good visibility between showers.
There is broken cloud with little low cloud.
Mainly snow showers due to low temperature but sometimes rain.
What kind of weather does the north westerly mP air mass bring to the UK?
Cold moist air that gets warmed from below over warmer land.
Rain showers occur mainly but can get snow in winter.
What kind of weather does the southerly cT air mass bring to the UK?
Hot dry air usually dust or sand laden.
Flows over colder land which cools it from below creating a stable atmostphere.
Generally hazey but if it crosses water than can get coastal fog.
What kind of weather does the easterly cP air mass bring to the UK in summer?
Hot dry, stable air (cooled from below)
What kind of weather does the easterly cP air mass bring to the UK in winter?
Cold dry unstable air, as it is heating from below.
If it crosses water it can become moist and mixed with the unstable air can cause snow showers.
What causes the rmP air mass?
A mP travels south but is met by a mT air mass which pushes it east and slightly back to the north.
