chapter 3 section 1 air masses and fronts. four major types of air masses in north america maritime...

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Chapter 3 Chapter 3 Section 1 Section 1 Air Masses and Air Masses and Fronts Fronts

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Page 1: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Chapter 3Chapter 3

Section 1Section 1

Air Masses and Air Masses and FrontsFronts

Page 2: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Four Major Types of Air MassesFour Major Types of Air Massesin North Americain North America

Maritime TropicalMaritime TropicalMaritime PolarMaritime PolarContinental TropicalContinental TropicalContinental PolarContinental Polar

Page 3: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Maritime TropicalMaritime Tropical

Warm, humid air masses form over oceans near Warm, humid air masses form over oceans near the tropicsthe tropics

Influence weather in the central & eastern United Influence weather in the central & eastern United States when formed over the Gulf of Mexico & the States when formed over the Gulf of Mexico & the Atlantic OceanAtlantic Ocean

Influence weather on the West Coast when formed Influence weather on the West Coast when formed over the Pacific Oceanover the Pacific Ocean

Summer – hot, humid weatherSummer – hot, humid weather Winter – humid air can bring heavy rain or snowWinter – humid air can bring heavy rain or snow

Page 4: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Maritime PolarMaritime Polar

Cool, humid air masses form over the icy Cool, humid air masses form over the icy cold North Pacific & North Atlantic oceanscold North Pacific & North Atlantic oceans

Affect the West Coast more than the East Affect the West Coast more than the East CoastCoast

In summer, often bring fog, rain, & cool In summer, often bring fog, rain, & cool temperatures to the West Coasttemperatures to the West Coast

Page 5: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Continental TropicalContinental Tropical

Hot, dry air masses form only in summer Hot, dry air masses form only in summer over dry areas of the Southwest & northern over dry areas of the Southwest & northern MexicoMexico

Covers a smaller area than other air massesCovers a smaller area than other air masses Move northeast, brings hot, dry weather to Move northeast, brings hot, dry weather to

the southern Great Plainsthe southern Great Plains

Page 6: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Continental PolarContinental Polar

Large masses that form over central & northern Large masses that form over central & northern Canada & AlaskaCanada & Alaska

Brings cool or cold airBrings cool or cold air In winter, bring clear, cold, dry air to much of North In winter, bring clear, cold, dry air to much of North

AmericaAmerica Can bring bitterly cold weather with very low Can bring bitterly cold weather with very low

humidity.humidity. In summer, storms may occur when air masses In summer, storms may occur when air masses

move south & meet maritime tropical air masses move south & meet maritime tropical air masses moving northmoving north

Page 7: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Four Types of FrontsFour Types of Fronts

Cold FrontsCold FrontsWarm FrontsWarm FrontsStationary FrontsStationary FrontsOccluded FrontsOccluded Fronts

Page 8: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Cold FrontsCold Fronts

When a rapidly moving cold air mass runs into a When a rapidly moving cold air mass runs into a slowly moving warm air mass, the denser cold air slowly moving warm air mass, the denser cold air slides under the lighter warm airslides under the lighter warm air

The warm air is then pushed upward resulting in a The warm air is then pushed upward resulting in a cold frontcold front

Cold fronts move quickly & can cause quick Cold fronts move quickly & can cause quick changes in the weather, including violent changes in the weather, including violent thunderstormsthunderstorms

Once a cold front moves through an area, cool, Once a cold front moves through an area, cool, dry air moves in and often brings clear skies & dry air moves in and often brings clear skies & cooler temperaturescooler temperatures

Page 9: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Warm FrontsWarm Fronts

A moving warm air mass collides with a slowly moving cold A moving warm air mass collides with a slowly moving cold air massair mass

As in a cold front, the warm air rises above the cold airAs in a cold front, the warm air rises above the cold air If the warm air is humid, showers & light rain fall along the If the warm air is humid, showers & light rain fall along the

front when the two air masses meetfront when the two air masses meet If the warm air is dry, scattered clouds formIf the warm air is dry, scattered clouds form Warm fronts move much slower than cold fronts, therefore, Warm fronts move much slower than cold fronts, therefore,

the weather may be rainy or foggy for several daysthe weather may be rainy or foggy for several days After a warm front passes through an area, warm & humid After a warm front passes through an area, warm & humid

weather will followweather will follow In winter, warm fronts bring snowIn winter, warm fronts bring snow

Page 10: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Stationary FrontsStationary Fronts

Sometimes cold & warm air masses meet, Sometimes cold & warm air masses meet, but neither has enough force to move the but neither has enough force to move the other; the result a stationary frontother; the result a stationary front

When the two air masses meet, water vapor When the two air masses meet, water vapor in the warm air condenses into rain, snow, in the warm air condenses into rain, snow, fog, or cloudsfog, or clouds

If the front is stalled, the weather may be If the front is stalled, the weather may be days of clouds & precipitationdays of clouds & precipitation

Sometimes cold & warm air masses meet, Sometimes cold & warm air masses meet, but neither has enough force to move the but neither has enough force to move the other; the result a stationary frontother; the result a stationary front

When the two air masses meet, water vapor When the two air masses meet, water vapor in the warm air condenses into rain, snow, in the warm air condenses into rain, snow, fog, or cloudsfog, or clouds

If the front is stalled, the weather may be If the front is stalled, the weather may be days of clouds & precipitationdays of clouds & precipitation

Page 11: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

Occluded FrontsOccluded Fronts

The most complex of the four frontsThe most complex of the four fronts At an occluded front, a warm air mass is caught At an occluded front, a warm air mass is caught

between two cooler air massesbetween two cooler air masses The two cooler air masses meet & may mixThe two cooler air masses meet & may mix Temperature near the ground becomes coolerTemperature near the ground becomes cooler The warm air mass is cut off (occluded) from the The warm air mass is cut off (occluded) from the

groundground As the warm air cools & its water vapor As the warm air cools & its water vapor

condenses, the weather may turn cloudy & rainy condenses, the weather may turn cloudy & rainy or snowyor snowy

Page 12: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

CyclonesCyclones

An area of relatively low air pressure is called a cycloneAn area of relatively low air pressure is called a cyclone Low air pressure is represented on a weather map as a Low air pressure is represented on a weather map as a LL Cyclone spin counterclockwise in the Northern HemisphereCyclone spin counterclockwise in the Northern Hemisphere Cyclones play a large part in the weather of the United Cyclones play a large part in the weather of the United

StatesStates As air rises in a cyclone, the air cools, forming clouds & As air rises in a cyclone, the air cools, forming clouds &

precipitationprecipitation Cyclones & decreasing air pressure are associated with Cyclones & decreasing air pressure are associated with

storms & precipitationstorms & precipitation

Page 13: Chapter 3 Section 1 Air Masses and Fronts. Four Major Types of Air Masses in North America  Maritime Tropical  Maritime Polar  Continental Tropical

AnticyclonesAnticyclones

Opposite of cyclones in most waysOpposite of cyclones in most ways Anticyclones are high-pressure centers of dry airAnticyclones are high-pressure centers of dry air High pressure areas are represented on a weather map as High pressure areas are represented on a weather map as

a a HH Anticyclones spin clockwise in the Northern HemisphereAnticyclones spin clockwise in the Northern Hemisphere Cool air moves downward from higher in the troposphereCool air moves downward from higher in the troposphere As the cool air falls, it warms up, so its relative humidity As the cool air falls, it warms up, so its relative humidity

dropsdrops Descending air in an anticyclone causes dry, clear weatherDescending air in an anticyclone causes dry, clear weather