What is pressure? Pressure is accumulative force of gas particles High Energy gas (HOT) has lots of movement, therefore.
Post on 27-Dec-2015
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What is pressure?
Pressure is accumulative force of gas particles
http://www.falstad.com/gas/
High Energy gas (HOT) has lots of movement, therefore high pressure
Low Energy (COLD) has less pressure
How do we measure pressure?Using a Barometer
The height of the Mercury Column is equal to the pressure acting on the surface of the mercury
P = gh
P = (density)(gravity)(height)
Two Types of Pressure Systems Occur in Nature
Low Pressure Systems - “Cyclones”
High Pressure Systems - “Anti-Cyclones”
Each type has specific characteristics related to the behavior of the gases that make up the system and how they interact with each other
High Pressure Systems - “Anti-Cyclones”
Winds blow outward and clockwise at surface
Associated with converging winds higher in the atmosphere
Weather: clear and “fair”
Low Pressure Systems
Winds blow inward and counterclockwise at surface
Associated with diverging winds higher in the atmosphere
Weather: cloudy with precipitation (rising air)
What is Wind?
Wind is the movement of Air
Wind forms as a result of three factors:
Pressure Gradient Force
Coriolis Effect
Friction with the Earth’s Surface:
Pressure Gradients
Air wants to move from high to low pressure (greater pressure difference = higher speed)
Isobars = lines of equal pressure
Coriolis Effect: Same effect as for ocean currents
Moving air (wind) is deflected to the right of intended path
Creates rotational movement
Friction with the Earth’s Surface
As air moves across the Earth’s surface, it is slowed by contact with features of the Earth’s surface
This slows down surface level winds, but also creates mixing because higher level winds continue at higher velocities
Wind is measured using two devices
SPEED is measured using an ANEMOMETER
DIRECTION is measured using a WEATHER VANE
• Local Winds are caused by temperature differences.
• Two common types include :Sea and Land Breezes: Occur in coastal areas
• Sea Breeze
• During the day, the land warms up because of the sun. Air rises over the land.
• To replace this air, cooler air from the sea flows towards the land (sea breeze)
• Land Breeze
• c. During the night, the ocean is warmer than the land. Air rises over the ocean.
• d. To replace this air, cooler air from the land flows towards the sea (land breeze)
• II. Mountain and Valley Breezes
• a. Valley Breeze: During the DAY air on the slopes of mountains heats up and moves up the mountain slope
• b. Mountain Breeze: At NIGHT air near the mountain top cools more quickly than air lower down, so it flows down slope towards the valley
Sea and Land Breezes (cont’d)
• Land Breeze
• During the night, the ocean is warmer than the land. Air rises over the ocean.
• To replace this air, cooler air from the land flows towards the sea (land breeze)
• Mountain and Valley Breezes
• Valley Breeze: During the DAY air on the slopes of mountains heats up and moves up the mountain slope
• Mountain Breeze: At NIGHT air near the mountain top cools more quickly than air lower down, so it flows down slope towards the valley
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