Module 5 Weather and Climate Flashcards
What is an air mass?
A large body of air, thousands of km2 across, with similar temperature and humidity in horizontal directions
What are source regions?
These are regions where air mass come from, they must be huge, a flat surface and have uniform characteristics and light winds.
What are some examples of good source regions and why?
The south pacific and south atlantic as well as the canadian/siberian arctic this is because these areas are high pressure areas (so we’ll see light winds) and have consistent high pressure centers.
Also the north atlantic and north pacific- no high pressure system dominate but is big area which gives consistent air masses.
Name the big 5 north american source regions
Continental artic
Continental polar
Maritime polar
Maritime tropical
Continental tropical
How do the naming conventions of air masses work?
The first letter describe the moisture content- c is for dry air masses and stands for continental
m is for moist air masses and stands for maritime
The second letter describe the temperature
The letter A stands for arctic (super cold)
The letter P stands for polar (pretty cold)
The letter T stands for tropical (warm)
Describe how different air masses have different movement patterns
Air masses will travel across certain trajectories which is set out by aloft winds (most are westerly) causing most air masses to shift west.
Describe how different air masses have characteristic stabilties
the cold air masses (such as the arctic and polar) were formed mostly by radiative cooling and will coldest at the bottom and therefore stable.
The warm air masses (the tropical) were formed by surface warming and therefore will be warm at bottom and unstable.
Describe the traits of continental artic air mass
very cold, very dry, very stable. Only forms in winter over frozen Arctic Ocean/snowy continent
Describe the traits of the continental polar air mass
not as cold, dry, or stable as continental arctic. Forms over snow-free continent.
Describe how the continental artic and continental polar air masses move
They move south down north america, the rockies act as boundary and stops these air masses from hitting BC
How do air masses die?
This is how air masses die… As they travel over different surface types, they GAIN the characteristics of that surface type. So in this case, the cA air warms, and gets more moist.
-Until, eventually, it loses its cA characteristics and you have to call it something else.
If you’re in calgary and the main air mass is a cA air mass what would the temperature and weather be like?
Be very cold as this is an arctic air mass, however would have clear skies and sun shining as this air mass is high pressure.
What is ‘Lake effect snow”
This when cA or cP air masses travel over a very large body of water, the warm water will contribute a warm and humid air mass, these air masses will mix because there’s a large vapour pressure gradient , cause mixing fog which then becomes cumulus clouds and precipitates when travelling up and away from lake which creates snow on land.
What is an example of a ‘lake effect snow” event?
The 2014 buffalo snow storm, caused 14 deaths
What are the characteristics of maritime polar air?
Cool, moist, often conditionally unstable near the ground; very cold, dry aloft. Forms in the pacific from dry cA air travelling across the ocean and gaining water at the bottom of the air mass but still being dry aloft and cold. Also forms in the north atlantic (but is less moist)
What happens when maritime polar air hits the rockies?
It will travel up the rockies and become colder and then precipitate it’s moisture as snow and rain then eventually travel down from the mountain as dry warm air (a chinook) and will now be called pacific air
Why will we never see mP maritime polar air masses in calgary?
Becuase by the time they cross the rockies they will have become pacific air, also they need eastward winds in order to hit north america which are uncommon
Describe the characteristics of maritime tropical air?
Warm, moist, unstable
Winter source area is the subtropical Pacific Ocean
Must travel 1600 km to hit West Coast, so very warm, moist by the time it arrives
What is the pineapple express?
Is a jet stream which is caused by the low pressure and high pressure fronts clashing in the pacific, this jet stream then flows towards north america and causes large amounts of ppt due to the mixing of air and moisture in it. Causes a chinook for us as it climbs over rockies
Describe when we’d see and what we’d experience of maritime tropical air (mT)
This air mass is only pushed inland through the wavy jet stream, if this happens in the summer time it will become very humid as the air mass brings a lot of ppt and very warm weather.
Describe characteristics of cT continental tropic air?
Very hot, dry, unstable
In N. America, only forms in N. Mexico / S.W. United States and only in summer
Produces very little precipitation, and can cause drought if it wanders far from home
forms in summer because land heats up quickly due to sun angle and solar insolation, when this air mas lifts it takes moisture w it causing drought in the area it was in before
What are fronts?
Fronts are boundaries between air masses with different properties
cold air is dense, has low humidity, and is associated with high pressure
Warm air is less dense, has high vapor content, and has low pressure
If these air masses collide we get a front
What determines what kind on front it is?
The front is determined by the type of air mass that’s moving into the area.
A cold front would be cold air enroaching on a warm air mass and a warm front would be warm air enroaching on a cold air mass.
Where is it likely to find stationary fronts?
Stationary fronts often have topograhc barriers that help produce them. For example rocky mountains help produce stationary front boundary naturally.
The stationary front could become a warm or cold front if one of the air masses begin to move
Define a stationary front?
A boundary between air masses with no movement.
Define a cold front?
An area where cold air (usually cA/cP or mP) is replacing warm air (mT or cT)
Describe every symbol on slide 26 of lecture 1
What are the indicators of a cold front?
Sharp temp change with much colder temperatures on one side of the front, a change in moisture, a change in wind direction (after passing turn west/northwest), a change in pressure, with falling pressure ahead of the front and rising behind, and see ppt such as snow
Why do you see low pressure in cold front before it reaches warm front?
Air behind cold front is bulldozer that pushes soft sand and materials in front of it, cold air hugs ground and pushes warm air aloft, this is why you see low pressure in cold fronts before it reaches warm air.
What type of clouds are created at a cold front? What type of clouds are created ahead of the cold front?
forced uplift of a warm (probably unstable) air mass, is going to create cumulonimbus clouds and precipitation.
We can also see that the wind aloft may form Cs/Ci clouds in advance of the front (could be a warning).
What type of ppt do we see at the cold front, what about after the cold front passes?
We see heavy showers of rain, snow at the cold front due to the burgeon process (warm air was uplifted and then water vapour in air condenses)
