air masses, weather, and fronts

An air mass is a large section of ______ with relatively uniform properties of _____ in the horizontal

troposphere, temperature and moisture

All air masses are described by both ______ and ______.

humidity, temperature

The types of air masses

The types of air masses

Maritime and Continental

Maritime air masses form over _____ and are ____.

large bodies of water, humid

Continental air masses form over ____ and are ____.

large land areas, dry

The terms used to describe the temperature of air masses in North America are ____, ____, and ____.

Arctic, Polar, Tropical

Arctic air masses are cold and form in ___ or at __.

the Arctic, high latitudes

Polar air masses form in the ______ by the heating of an _____ or the cooling of a _____.

temperate zones (permafrost line to 30°N), Arctic air mass, Tropical air mass

Tropical air masses are warm and from in ____ or ____.

tropics, low latitudes (between 30°N and the equator)

The four air masses commonly found in NA are:

• Continental Arctic (cA)

• Continental Polar (cP)

• Maritime Polar (mP)

• Maritime Tropical (mT).

Define a front

The transition zone between two air masses

Since NA has 4 air mass structures, there are ___ frontal boundaries

3

Define a cold front

Advancing cold air that undercuts the warm air

Define a warm front

Cold air that retreats and gives way to hot air which is less dense and slides over the cold air

Define a stationary front

A transition zone between 2 air masses that are not moving

What is Polar Front Theory?

States that the Earth is covered by polar air in polar regions and tropical air in the equatorial regions. They are separated by the polar front; it is a 2 air mass, one-front model.

What is the term for an air mass formed in temperate zones?

Polar

What are the factors that affect the severity of weather created by a front?

• The slope of the frontal surface

• The speed of frontal movement

• The temperature of the lifted air mass

• The moisture content of the lifted air mass

• The stability of the lifted air mass

Most troughs bring ____ particularly following the passage of a trough

clouds, showers, and a wind shift

Ridges tend to bring _____ weather since air is often _____ within a ridge

warmer and drier, sinking

Before a cold front arrives, the wind ahead of the front is typically out of ____. Once the front passes through, the wind will usually ____ around to _____.

the SSW, veer around, the WNW

Before a warm front arrives, the wind ahead in the front is typically from _____, but once the front passes through, the wind usually _____ to ____.

the east, veers around, the SSW

The wind shift that occurs at the frontal surface is most significant ___. The wind shift associated with flight through a front is more abrupt ____.

in the lower levels, at a cold front than a warm front

Visibility can be reduced well in advance of warm fronts because of ____ and the ____.

the shallow slope, generally large band of cloud and precipitation

Ahead of cold fronts, visibility is generally ___. Close to the front, visibility may be reduced in _____.

good, precipitation and mist

After the passage of a cold front, there will usually be ______ in visibility. The air behind the front is usually unstable, and the vertical currents will carry _____.

a marked improvement, suspended particles aloft

Any part of an air mass that is _____ and has recently passed over an industrial region will be loaded with ____ and have poorer visibility than usual

stable, pollutants

Which of the following is not one of the four types of air masses in North America?

Continental Maritime (cM)

Dew point temperatures generally ____ with a warm frontal passage and ____ with a cold frontal passage

increase, decrease

Fronts are generally associated with ____.

areas of low pressure

Because cold air is denser than warm air, once the cold front has passed a location, the pressure will begin to ____.

rise

Which type of front has reduced visibility well in advance of the front?

Warm front

Most ____ bring clouds, showers, and a wind shift, while ____ tend to bring fewer clouds and drier weather.

troughs, ridges

At a warm front, three factors determine the type of cloud and precipitation:

• The moisture content of the overrunning warm air

• The stability of the overrunning warm air

• The degree of overrunning

Define the degree of overrunning

The pressure gradient of the warm air and angle of warm air motion relative to the frontal surface

At a cold front, three factors determine the type of cold and precipitation

• The moisture content of the lifted warm air

• The stability of the lifted warm air

• The degree of lift

The arrival of a cold front will generally result in a ____ in surface temperature.

sudden decrease

What causes frontal turbulence?

All of these

The slope of the frontal surface and the speed of frontal movement are factors that determine the severity of _____ created by a front.

weather