Chapter 11 Air Masses and Fronts Flashcards
what is an air mass?
large region of air with similar temp and humidity
-when air is in contact w/ground, it picks up traits
what is a source region?
where air mass comes from
best source regions are:
-flat
-uniform
-calm winds
-air stays in contact w/ground
how do we classify air masses?
classification based upon temperature and humidity
temp:
P= polar
T= tropical
A= arctic
humidity:
m= maritime, humid
C= continental, dry
Explain cP (continental polar) and cA (continental arctic)
forms: Canada, north pole
cold, dry = stable
Arctic air is more extreme (can only be dry and not humid)
-can cause lake effect snow (when cold, dry air mass moves over a warm body of water)
-can form in the summer
-eventually loses characteristics
explain mP (maritime polar)
forms: N. Pacific (west to east), and N. Atlantic (east to west *rare, colder)
cool+humid=unstable, cloud cover + precip
explain mT (maritime tropical)
forms: over warm ocean, from SE Pacific (pineapple express), from SW Atlantic (bermuda high)
warm+humid=unstable, heavy precip, vertical clouds
explain cT (continental tropical)
forms: summer only, SW desert/Mexican Plateau
hot+dry=stable
what is a front?
the transition zone between two air masses of different densities
what characteristics do we use to identify changes on charts?
- sharp temperature change
- sharp change in dew point
- shift in wind direction
- sharp pressure change
- clouds and precipitation
what is a stationary front?
boundary between air masses that aren’t moving
what is a cold front?
cold air is replacing warm air
-warm air rises quickly because its unstable
-quick rise=vertical cloud development, thunderstorms
what is a warm front?
warm air replaces cold air
-less dense air comes in, goes over dense air
-long rise=horizontal stratus clouds
-moves .5 as fast as cold front
what is an occluded front?
cold front catches up to and overtakes a warm front
what is a dry line?
boundary between different humidities, but not different temps
