25 terms

Ch 12 Meteorology

Current short-term state of the atmosphere. Example weather statement: "It's raining."
Air Mass
A large body of air that takes the characteristics (humidity, temperature) of the area over which it forms.
Source region
Region over which an air mass forms.
** Example: The source region for a Maritime Tropical air mass might be the Gulf of Mexico.
HUMID air mass that forms over oceans. Represented by a lower-case "m".
DRY air mass with very little water vapor because it forms over large land area (Over a continent, not an island). Represented by a lower-case "c".
WARM air mass because it forms relatively near the equator. Represented by a capital "T".
COLD air mass because it forms relatively near the poles. Represented by a capital "P".
Arctic Air Mass (A)
Similar to a cP (Continental Polar) air mass but MUCH, MUCH colder.
Air Mass Modification
It is the change in humidity or temperature of an air mass as it moves away from its source region.
Humidity: An air mass becomes more humid if it moves over an ocean, and drier if it moves over land.
Temperature: An air mass becomes warmer if it moves towards the equator, and colder if it moves towards the poles.
Boundary between two air masses of different temperatures
Cold Front
*What type of air mass is pushing?
*What type of clouds?
*Represented by??
Cold, dense air is moving and displaces (pushes)warm air up along a steep front. A narrow band of clouds (cumulonimbus), showers, thunderstorms, or heavy snow may occur. As the storm passes, a drop in temperature occurs.

Blue line with blue triangles pointing in the direction the cold air is moving. (Your lips turn "blue" when you're cold. Triangles are like "icicles".)
Warm Front
*What type of clouds?
*Represented by?
Moving warm air displaces (pushes) cold air. The warm air rises in a gentle slope over the cold air.

Many types of clouds are formed at all levels of the troposphere: cirrus, altocumulus, nimbostratus, etc.

This forms a wide band of cloudiness and precipitation.

Red line with red semi-circles pointing the direction the warm air is moving. (Red semi-circles are like hot burners on a stove.)
Stationary Front
Front that doesn't move because there isn't much temperature difference between the 2 colliding air masses.

Varying weather possible: Clear vs. clouds, light or no precipitation vs. thunderstorms, no rain vs. days of rain.

Combo of cold & warm diagrams with short segments of alternating blue triangles & red semicircles pointing in opposite directions

Image from: http://library.thinkquest.org/C0125863/weather/image/front_stationary_en.gif
Occluded Front
Formed when a Cold Front catches up and passes a Warm Front, forcing the warm air up and running into another cold air mass. The warm air is "occluded" and "shut out" and no longer touches the ground.

Purple line with triangles & semi-circles on SAME side of line, as all 3 air masses are moving in same direction.
Images from: http://kidlat.pagasa.dost.gov.ph/genmet/fronts/occludedfront_b.gif
High Pressure
pressure system with clockwise and outward winds that bring clear blue skies and dry weahter

It this air pressure system air sinks, so that when it reaches Earth's surface, it spreads away from the center. this pressure system rotates in a counterclockwise direction
Low Pressure
pressure system with counterclockwise and inward winds that brings cloudiness and stormy weather

A mass of rising warm air that usually bring wet, stormy weather. Some inbalance in temperature, pressure or density causes part of the front to move north as a warm front, this sets up a counterclock wise or cyclonic circulation.
Station Model
Use of symbols to record the weather data for a particular site at a particular time.
Lines that connect points of equal or constant values.
("Iso" is "same", like an isoceles triangle.)
lines on a map drawn through all points having the same atmospheric pressure
lines that connect points that have the same temperature
Maritime Tropical (mT)
Humid, warm air mass that forms over a warm ocean like the Gulf of Mexico
Maritime Polar (mP)
Humid, cold air mass that forms over icy, cold oceans such as the North Pacific, Atlantic and Artic Oceans. This type of air mass brings cool air, fog, clouds, & rain to NW United States.
Continental Tropical (cT)
Dry, warm air mass that forms over land in tropical regions like Mexico, Sahara Desert.
Continental Polar (cP)
Dry, cold air mass that forms over cold land, like northern Canada.
Long-term variation of weather in a particular area, averaged over 30 years.