Air Masses and Fronts Flashcards
Where does most inclement weather occur?
At, and caused by fronts
What is an airmass and how large is it?
It is a large volume of air, which in uniform in temperature and moisture.
It can extend 1000 km across the surface and reach from the ground to the stratosphere, 16km high.
True or False?
When air masses move they lose their source region’s characteristics.
False, they carry their weather conditions (moisture, temperature) from their source region.
Air masses that clash with different temperatures and humidity may cause what?
Inclement weather, or severe storms
On a map, air masses are classified with a low and upper case letter. What do these signify?
Lowercase: Moisture in air mass
Uppercase: Describes heat in the air mass
What are the moisture and temperature categories regarding air masses?
Maritime & continental
Arctic, polar, tropical and equator.
The warmer the air mass, the _____ and _____ its tropopause.
Higher and colder
Which air masses have a medium, high and very high tropopause?
Medium: mP
High: mT
Very High: cT
Describe a mP airmass
Cool, moist and unstable
Forms over northern Pacific/ Atlantic.
Ocean surface temperatures normally warmer than land, leads to mP to be milder than cP or cA.
Leads to low stratus, fog and periods of cool temperatures in summer
Describe a mT airmass
Warm and very humid/ unstable throughout
Forms over Gulf of Mexico, Caribbean Sea, western Atlantic and subtropical Pacific.
Associated with cumulus development, thunderstorms and showers.
Advection fog in the winter
What are the temperature ranges of mA, mP and mT?
mA: 1C to -15C
mP: 15C to 25C
mT >25C
Air masses frequently move, resulting in their characteristics to change. Modification may occur and the degree depends on?
Their speed
Moisture/ dryness of the new region
Temperature difference between new surface and air masses
Warming from below develops _____ and _____ in the lower levels of the atmosphere.
Instability and convection
Cooling from brlow causes increased _____ in the lower levels.
Stability
What does cooling from below block so any modifications of moisture and temperature are isolated to the lower thousand feet?
Vertical motion
If a cold air mass gets warmed and moistened from below as it moves south, what is produced?
Instability, turbulence, convective clouds and showers. cA is an example of this.
What is the transition between air masses where temperatures change rapidly called?
Fronts or frontal systems
What happens in a front or frontal system?
A rapid horizontal and moisture change in the mixing zone, approx. 10 - 100 km across.
What are common air masses found in Canada?
cA, mA, mP and mT
On a frontal wave, where is the low located?
Wave crest where the two fronts meet at the point
Which front has the greater lift?
Cold front
What is a protruding nose?
When the speed of a cold front is relatively high and surface friction large enough, a protruding nose will develop in lower thousand feet.
A quasi, warm and cold front have what degree of slopes?
Quasi: 1Deg
Warm: 1/2 Deg
Cold: 1 1/2 Deg
Where can upper fronts occur?
Anywhere where very cold air is trapped on the surface, can be either cold or warm fronts.
