Air Masses and Fronts

Question 1

Where does most inclement weather occur?

Answer 1

At, and caused by fronts

Question 2

What is an airmass and how large is it?

Answer 2

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.

Question 3

True or False?

When air masses move they lose their source region’s characteristics.

Answer 3

False, they carry their weather conditions (moisture, temperature) from their source region.

Question 4

Air masses that clash with different temperatures and humidity may cause what?

Answer 4

Inclement weather, or severe storms

Question 5

On a map, air masses are classified with a low and upper case letter. What do these signify?

Answer 5

Lowercase: Moisture in air mass

Uppercase: Describes heat in the air mass

Question 6

What are the moisture and temperature categories regarding air masses?

Answer 6

Maritime & continental

Arctic, polar, tropical and equator.

Question 7

The warmer the air mass, the _____ and _____ its tropopause.

Answer 7

Higher and colder

Question 8

Which air masses have a medium, high and very high tropopause?

Answer 8

Medium: mP

High: mT

Very High: cT

Question 9

Describe a mP airmass

Answer 9

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

Question 10

Describe a mT airmass

Answer 10

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

Question 11

What are the temperature ranges of mA, mP and mT?

Answer 11

mA: 1C to -15C
mP: 15C to 25C
mT >25C

Question 12

Air masses frequently move, resulting in their characteristics to change. Modification may occur and the degree depends on?

Answer 12

Their speed
Moisture/ dryness of the new region
Temperature difference between new surface and air masses

Question 13

Warming from below develops _____ and _____ in the lower levels of the atmosphere.

Answer 13

Instability and convection

Question 14

Cooling from brlow causes increased _____ in the lower levels.

Answer 14

Stability

Question 15

What does cooling from below block so any modifications of moisture and temperature are isolated to the lower thousand feet?

Answer 15

Vertical motion

Question 16

If a cold air mass gets warmed and moistened from below as it moves south, what is produced?

Answer 16

Instability, turbulence, convective clouds and showers. cA is an example of this.

Question 17

What is the transition between air masses where temperatures change rapidly called?

Answer 17

Fronts or frontal systems

Question 18

What happens in a front or frontal system?

Answer 18

A rapid horizontal and moisture change in the mixing zone, approx. 10 - 100 km across.

Question 19

What are common air masses found in Canada?

Answer 19

cA, mA, mP and mT

Question 20

On a frontal wave, where is the low located?

Answer 20

Wave crest where the two fronts meet at the point

Question 21

Which front has the greater lift?

Answer 21

Cold front

Question 22

What is a protruding nose?

Answer 22

When the speed of a cold front is relatively high and surface friction large enough, a protruding nose will develop in lower thousand feet.

Question 23

A quasi, warm and cold front have what degree of slopes?

Answer 23

Quasi: 1Deg
Warm: 1/2 Deg
Cold: 1 1/2 Deg

Question 24

Where can upper fronts occur?

Answer 24

Anywhere where very cold air is trapped on the surface, can be either cold or warm fronts.

Question 25

Where does a front typically lie?

Answer 25

A trough of low pressure

Question 26

What are the two type of occlusion?

Answer 26

Cold and Warm

Question 27

Explain the occlusion process

Answer 27

The cold air mass overtaking the warm front is either colder or warmer than the cool air ahead of the warm front. In either case, the cold air rides under or over the cool air ahead and lifts the warm air.

Question 28

What is a trowal?

Answer 28

TROugh of Warm Air Aloft

Question 29

Which frontal surfaces does a trowal consist of?

Answer 29

Cold and warm front aloft, in a V shape.

Question 30

Where does the trowal start and move towards or from?

Answer 30

Starts on the ground and moves away from the wave crest.

Question 31

Briefly explain the winds, temperature, pressure, clouds, precipitation and visibility of a cold front before/ while / after passing.

Answer 31

Winds: SE-SW / gusty & shifting / SW- NW
Temp: Warm / sudden drop / steadily dropping
Pressure: falling steadily / sudden drop / rising
Clouds: Increasing CI, CS, CB / CB / CU
Precip: Short periods of showers / heavy rains w/ TS and lightning / showers then clearing
Visibility: fair to poor in haze / poor, but improving / good except in showers.

Question 32

Briefly explain the winds, temperature, pressure, clouds, precipitation and visibility of a warm front before/ while and after passing.

Answer 32

Winds: SE - SW / variable / SE - SW
Temp: cool - cold, slow warming / steady rise / warmer then steady
Pressure: usually falling / leveling off / slight rise then fall
Clouds: CI, CS, AS, NS ST, Fog / NS or ST / Clearing, scattered SC
Precip: Light, moderate and heavy / drizzle or none / usually none
Visibility: Poor / poor but improving / fair in haze

Question 33

Which air masses is generally a wintertime air mass?

Answer 33

cA

Question 34

Which air mass affects most of Canada all summer?

Answer 34

mP

Question 35

Which air mass is a spring and fall air mass or winter in coastal BC for Canada?

Answer 35

mA