Atmospheric Movement and Local Weather

Let’s Review

1. Air Masses Bodies of air with about the same temperature and humidity throughout

2. Air Pressure a measure of the weight of the atmosphere on a given area (barometric pressure). Measured with a barometer.

3. Anemometer – instrument used to measure wind speed

4. Atmosphere – the gasses held to Earth by gravity; the most dense are held near the surface.

MoreDirect Sun Hot 0 o Equator 30 o S 60 o S 90 o S 30 o N 60 o N

5. Convection Currents – cyclical (circular) currents caused by density differences

Global Convection Cells

6. The Coriolis Effect – effect of Earth’s rotation on the path of air and water. Causes paths to curve.

Forms high in the upper Troposphere between two air masses of different temperatures Higher temperature difference = faster speed Due to the Coriolis Effect, it flows around air masses. Polar Jet: It dips southward when frigid polar air masses move south. It tends to stay north in the summer months Jet Stream

Abnormally high surface ocean temperatures off the coast of South America Causes unusual weather patterns across the globe 7. El Nino – period when Pacific surface waters are warmer than normal; impacts temperature and rainfall in U.S.

8. Humidity – amount of water vapor present (dissolved) in the air.

http://www.pbs.org/wgbh/nova/vanished/jetstr_five.html 9. Jet Stream – narrow bands of high speed wind high in the atmosphere. Moves west to east in Northern Hemisphere.

10. La Nina – period when surface waters in Pacific are unusually cool; impacts temperatures and rainfall in the U.S.

11. Prevailing Winds - global wind currents at mid-lattitudes; mostly blows in one direction

12. Psychrometer – instrument used to measure humidity in the air

Gulf Stream A strong surface current Begins at the tip of Florida Flows up the eastern coastline of the U.S. Crosses the Atlantic Ocean Causes warmer climate in NW Europe Gulf Stream

Why does the Earth have wind and ocean currents? Reflection Question

Variables Affecting Local Weather

When convection and winds cause air masses to move, they bump into one another. The area where two air masses meet is called a front. Most severe weather occurs near frontal boundaries. 13. Weather Fronts – area where two air masses with different temperatures and pressures meet.

Cold Front - Cold air meets warm air - Fast moving and stormy, severe weather is likely

Cold Front Symbol

Warm Front - Warm air meets cold air - Slow moving with less severe weather

Warm Front Symbol

Warm and cool air masses that are not strong enough to move one another Sits still for a long period of time Stationary Front

Stationary Front Symbol

Friction

Frontal Boundary Simulations http://www.phschool.com/atschool/phsciexp/acti ve_art/weather_fronts/ Frontal Boundary Simulations

High and Low Pressure Circulation

Air pressure is measured with a barometer in millibars. Millibars are represented by connected lines of equal pressure. This is a lot like the topographic map lines. The closer together the lines are, the faster the wind speed. The farther apart the lines are, the slower the wind speed. Air Pressure and Wind

The Earth’s Insulator The Sun heats the water and land every day. Land heats up rapidly, but cools off rapidly. Desert Water heats up slowly, but cools off slowly. Swimming at night The heat retained by the oceans is what keeps our planet insulated. The Earth’s Insulator

The heating and cooling of water and land produces land breezes and sea breezes. High pressure moves toward low pressure, pushing the warm air upward. As warm air rises, cooler air moves in and replaces it. Land and Sea Breezes

Land Breeze

Sea Breeze

Sea Breeze and Land Breeze Simulation http://www.classzone.com/books/earth_science /terc/content/visualizations/es1903/es1903pag e01.cfm?chapter_no=visualization Sea Breeze and Land Breeze Simulation

How do global patterns of atmospheric movement affect local weather? Reflection Question