WINDWIND

What do wind patterns have to do What do wind patterns have to do with oceans?with oceans?

They impact currents, They impact currents, waves, and weatherwaves, and weather

Review…Review… Warm air is less dense than cold air, Warm air is less dense than cold air,

because the heating makes the molecules because the heating makes the molecules move faster and farther apart, and this move faster and farther apart, and this causes warm air to rise.causes warm air to rise.

Cool air will flow towards and under warm Cool air will flow towards and under warm air, pushing it up and away.air, pushing it up and away.

At the equator, the surface and the air is warmer than at any other latitude

At the poles the coldest densest air exists.

The cold air from the poles moves along the earth’s surface toward the warmer regions.

The air that is heated and rises at the equator heads northward or southward, but cools before it can reach the poles.

By the time warm air from the equator reaches north or south latitudes of about 30 degrees, it has cooled so much and become so dense that it begins to drop back to Earth’s surface.

For the cold air leaving the poles, once it has reached a latitude of 60 degrees it has warmed enough to start to rise

The result is 3 closed patterns of air movement in each Hemisphere.

Hadley cellHadley cell - Low latitude air movement - Low latitude air movement toward the equator; rises vertically. toward the equator; rises vertically.

Ferrel cellFerrel cell - A mid-latitude atmospheric - A mid-latitude atmospheric circulation cell; air flows poleward and circulation cell; air flows poleward and eastward near the surface and equatorward eastward near the surface and equatorward and westward at higher levels. and westward at higher levels.

Polar cellPolar cell - Air rises and travels toward the - Air rises and travels toward the poles where it sinks, forming the polar highs. poles where it sinks, forming the polar highs. At the surface air diverges outward and At the surface air diverges outward and these surface winds create polar easterlies. these surface winds create polar easterlies.

Jet StreamsJet StreamsJet streams are ribbons of extremely fast moving air near the troposphere. The Troposphere is the lowermost portion of Earth's atmosphere.

Caused by the contact between warm and cold air

Found at boundaries between the polar and temperate zones and between temperate zones and tropical zones

Wind speeds in a jet stream can vary from 100 km/h to 300 km/h

They are thousands of kilometers long, a few hundred kilometers wide and two or three kilometers thick

In general, the weather north of a jet stream is cold, while the weather south of a jet stream is warmer

Location of the Jet Location of the Jet Location of the JetLocation of the JetStream in the SummerStream in the Summer Stream in the WinterStream in the Winter

Based on the previous two diagrams that showed the general location of the jet stream in winter and summer how can these be used to explain our seasonal temperature changes here in Nova Scotia?

AIR MASSESAIR MASSESAlthough air is usually in motion, due to Although air is usually in motion, due to convection and the Coriolis effect, large convection and the Coriolis effect, large portions of air often remain in nearly the same portions of air often remain in nearly the same place long enough to take on the temperature place long enough to take on the temperature and moisture characteristics of the land or and moisture characteristics of the land or ocean below. When this occurs, a large portion ocean below. When this occurs, a large portion of the air is nearly uniform in temperature and of the air is nearly uniform in temperature and humidity and we have an AIR MASS.humidity and we have an AIR MASS.

Air Masses are classified as CONTINENTAL or MARITIME, depending on whether they form over land or ocean.

Air masses are also classified as POLAR or TROPICAL depending on their temperature.

maritime polarmPmaritime

polar mP

continental polar cP

maritime tropical mT

maritime tropical mT

continental tropical

cT

Characteristics of Air MassesCharacteristics of Air Masses

Continental Polar - Cool and Dry

Maritime Polar - Cool and Moist

Continental Tropical - Warm and Dry

Maritime Tropical - Warm and Moist

Pressure SystemsPressure Systems

A region of the earth’s atmosphere where air A region of the earth’s atmosphere where air pressure is unusually high or low.pressure is unusually high or low.

High Pressure SystemsHigh Pressure Systems

Any region where air is descending (and therefore exerting more pressure on the area below)

High pressure systems occur when an air mass forms over cold ground, so that the air cools by conduction and convection. These systems are associated with clear, cool weather. Think: COLD SNAPS!

They flow clockwise in the N. hemisphere and counterclockwise in the S. hemisphere.

Any region where rising air is leaving dense air below. Intense heating of the ground can create a low pressure system

Low pressure systems are generally very warm and they can lead to storms and tropical cyclones.

They flow counter clockwise in the N. hemisphere and clockwise in the S. hemisphere.

Low Pressure SystemLow Pressure System

Hurricanes:Hurricanes: A hurricane is a severe tropical storm, that forms in A hurricane is a severe tropical storm, that forms in

the southern Atlantic Ocean, Caribbean Sea, Gulf the southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico or in the eastern Pacific Ocean.of Mexico or in the eastern Pacific Ocean.

Hurricanes need warm tropical oceans, moisture Hurricanes need warm tropical oceans, moisture and light winds above them. and light winds above them.

If the right conditions last long enough, a hurricane If the right conditions last long enough, a hurricane can produce violent winds, incredible waves, can produce violent winds, incredible waves, torrential rains and floods. torrential rains and floods.

Hurricanes rotate in a counterclockwise direction Hurricanes rotate in a counterclockwise direction around an "eye." around an "eye."

Hurricanes have winds at least 100km per hour. Hurricanes have winds at least 100km per hour. There are on average six Atlantic hurricanes each There are on average six Atlantic hurricanes each

year.year. June 1 to November 30 is called hurricane season.June 1 to November 30 is called hurricane season.

HurricanesHurricanes

At 12:10 a.m. ADT, Monday September 29, 2003, Hurricane Juan At 12:10 a.m. ADT, Monday September 29, 2003, Hurricane Juan made landfall in Nova Scotia as one of most powerful and made landfall in Nova Scotia as one of most powerful and damaging hurricanes to ever affect Canada. damaging hurricanes to ever affect Canada.

http://www.youtube.com/watch?v=H9VpwmtnOZc (hurricane destruction) (hurricane destruction)

http://www.youtube.com/watch?v=4f45jA5UxB0 (how a hurricane is born) (how a hurricane is born)

To Study, Write Definitions To Study, Write Definitions for the Terms Below:for the Terms Below:

Cells Cells – Hadley, Ferrel, and Polar– Hadley, Ferrel, and Polar Jet StreamsJet Streams Air Masses Air Masses – Continental, Maritime, Polar, – Continental, Maritime, Polar,

TropicalTropical Pressure System Pressure System – High, Low– High, Low HurricanesHurricanes