Local Winds

What causes local winds? Local winds: change daily, flow within a small area, typically flow in a regular pattern How would this local wind pattern change at night? NSF North Mississippi GK-8

NSF North Mississippi GK-8 Local Winds NSF North Mississippi GK-8

NSF North Mississippi GK-8 Science Starter: Two barometers are placed one kilometer apart. One shows higher pressure than the other. What will happen to the air between them? NSF North Mississippi GK-8

Global Winds

NSF North Mississippi GK-8 Global Winds Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles. NSF North Mississippi GK-8

Calm Regions & Global Wind Belts (1) Doldrums: Low pressure zone @ equator Warm air rises & spreads toward poles Rising moist air -->clouds & heavy rain (2) Horse Latitudes: High pressure zones @ 30˚ N/S Warm air from equator cools & sinks Clear & dry weather Air usually stays calm in high/low pressure zones. Winds are light & often change direction. NSF North Mississippi GK-8

NSF North Mississippi GK-8 Global Winds Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles. NSF North Mississippi GK-8

NSF North Mississippi GK-8 Global Wind Belts: Trade Winds: Blow East from Horse latitudes to Equator Strong & steady. Die out as they reach equator Westerlies: (blow from the West) Blow from Horse latitudes to poles Bring storms across U.S. Dense air (in horse latitudes & other high pressure zones) moves toward low pressure zones (like the doldrums) NSF North Mississippi GK-8

NSF North Mississippi GK-8 Global Winds Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles. NSF North Mississippi GK-8

NSF North Mississippi GK-8 Easterlies: (blow from East) Blow from polar regions to mid-latitudes NSF North Mississippi GK-8

NSF North Mississippi GK-8 Global Winds Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles. NSF North Mississippi GK-8

Science Starter: Calm Areas and Wind Belts Name Characteristics (1) A low-pressure zone near the equator. (2) High-pressure zone at about 30° N and 30° S of the equator. (3) Winds that blow from the East from the horse latitudes to the equator. (4) Winds that blow from the West from the horse latitudes to the poles. NSF North Mississippi GK-8

Jet Streams Flow Near the Top of the Troposphere Jet Stream: Long distance wind that flows in the upper Troposphere. Not all long distance winds travel @ Earth’s surface. Jet Streams: Flow in a wavy pattern, move from W -->E, can pull cold air down into US, pull warm air up into Canada, flow faster than surface winds Each hemisphere has 2 jet streams: (1) Polar jet stream (2) Subtropical jet stream NSF North Mississippi GK-8

NSF North Mississippi GK-8 Air Masses (2 words) Air mass takes on characteristics of where it formed: 1. First Word: moisture Continental (land) Maritime (water) 2. Second Word: temperature Tropical (warm) Polar (cold) Continental p. 80 (in text) NSF North Mississippi GK-8

NSF North Mississippi GK-8 Fronts A front is the boundary separating air masses of different densities Fronts extend both vertically and horizontally in the atmosphere p. 83 (in textbook) NSF North Mississippi GK-8

NSF North Mississippi GK-8 Fronts: 1. Cold Front: The zone where cold air is replacing warmer air In U.S., cold fronts usually move from northwest to southeast NSF North Mississippi GK-8

As the warm air meets the cold air, it condenses into clouds. Cold fronts produce cumulonimbus clouds and precipitation. Brief, heavy storms are likely. After the storms, the air is cool and often very clear.

NSF North Mississippi GK-8 Fronts: 2. Warm Front: The zone where warm air is replacing colder air In U.S., warm fronts usually move from southwest to northeast Air gets more humid after a warm front moves through NSF North Mississippi GK-8

Warm fronts move more slowly than cold fronts. The warm air gradually moves up and over the cold air mass. The clouds form slowly along the front producing cloud covered skies. A warm front may bring hours of steady rain or snow. After the front passes, the air is warmer.

NSF North Mississippi GK-8 Fronts: 3. Stationary Front: When either a cold or warm front stops moving When the front starts moving again it returns to either being a cold or warm front NSF North Mississippi GK-8

When cold and warm fronts stop moving. The air in each mass can still move sideways along the front or upwards.. The upward motion produces clouds. The clouds may stay in the sky for days at a time.

http://www.wunderground.com

http://www.youtube.com/watch?v=stX1Avy4qHg http://www.youtube.com/watch?v=LN5Izcf-z9k http://www.youtube.com/watch?v=NTjR91JC850

Create Front Flip Chart here.

High and Low Pressure Systems The “H” or the “L” on the map mark the highest or lowest pressure in the area. The highs and lows cause a whole weather system to develop in the region.

High Pressure Centers In a high pressure area, air slowly sinks and spreads out to lower pressure areas. In the northern hemisphere the Coriolis Effect causes the air to move clockwise. The air has to move all the way around the center before it can be a pressure center.

When the high pressure system stays in one place for some time, it may become an air mass. It generally brings warm air, clear skies and gentle breezes. It happens because as the air sinks it starts to warm up. Clouds often disappear.

Low Pressure Centers These can also form as air moves inward in a counter-clockwise motion. It then moves upward to higher altitudes. As the air moves up, the pressure lowers and the air moves faster. Rising air produces stormy weather.

One place low pressure centers often form is near a stationary front. The cold front moves one way, the warm front moves the other way. The low pressure center is formed where the two boundaries meet.

http://www.windows2universe.org/earth/Atmosphere/high_pressure.html http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=11447 http://explore.ecb.org/videos/VLC_media?P1=VLC035&REFERER=OTHER https://www.meted.ucar.edu/loginForm.php?urlPath=tropical/met_topics&go_back_to=http%253A%252F%252Fwww.meted.ucar.edu%252Ftropical%252Fmet_topics%252Fprint.htm##