1.  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

3.  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)

4.  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

5.  High Pressure Systems - “Anti-Cyclones”  Winds blow outward and clockwise at surface  Associated with converging winds higher in the atmosphere  Weather: clear and “fair”

6.  Low Pressure Systems  Winds blow inward and counterclockwise at surface  Associated with diverging winds higher in the atmosphere  Weather: cloudy with precipitation (rising air)

7.  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:

8.  Pressure Gradients  Air wants to move from high to low pressure (greater pressure difference = higher speed)  Isobars = lines of equal pressure

9.  Coriolis Effect: Same effect as for ocean currents  Moving air (wind) is deflected to the right of intended path  Creates rotational movement

10.  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

11.  Wind is measured using two devices  SPEED is measured using an ANEMOMETER  DIRECTION is measured using a WEATHER VANE

12. 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

13. 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)

14. Day = Sea Breeze Night = Land Breeze

15. 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

16. Valley Breezes Mountain Breezes