1. How are clouds formed. Weather
Clouds form when air is cooled to its dew point as it rises.

2. Air Pressure and Wind

3. What is Air Pressure? Video
Air pressure is the pressure exerted by the weight of air above
Exerted in all directions (up, down, and sideways)
The air pressure pushing down on an object exactly balances the air pressure pushing up on the object
Average Air Pressure at sea level is
1 kg/cm2, mb, or in. of mercury

4. Measuring Air Pressure
Barometer: device used for measuring air pressure
Unit:
millibars (mb)
inches of mercury
Torricelli: invented the mercury barometer in 1643

5. Wind – What causes it?
Wind is a result of horizontal differences in air pressure
Air flows from areas of high pressure to areas of lower pressure.
Video

6. How do we get pressure differences on Earth?
The unequal heating of earth’s surface generates pressure differences
Solar radiation is the ultimate energy source for most wind

7. Factors Affecting Wind
Pressure Differences
Coriolis Effect

8. Pressure Differences Isobars
lines on a map that connect places of equal air pressure
A pressure gradient
The spacing of isobars indicates the amount of pressure change over a given time

9. Isobars
Closely spaced isobars: indicate a steep pressure gradient and high winds.
Widely spaced isobars: indicate a weak pressure gradient and light winds.

10. Coriolis Effect
The Coriolis effect describes how Earth’s rotation affects moving objects.
Northern Hemisphere
Deflected to right,
Moves counterclockwise
Southern Hemisphere
Deflected to the left,
Moves clockwise

11. Jet Streams Animation Jet streams are fast-moving rivers of air
Speed: 120 and 240 kilometers per hour
Direction: West-to-east direction.
Drive weather systems
Animation

12. High and Low Pressure System
Low Pressure Centers
High Pressure Centers
Centers of
Low Pressure
High Pressure
AKA
Cyclones
Anti-cyclones
Pressure Behavior
Pressure drops
Pressure increase
Wind Behavior
Winds blow counterclockwise
Winds blow outward and clockwise
Weather Associated
Severe and stormy
Fair and Sunny
Symbol
“L” that is RED
“H” that is BLUE

13. Measuring Wind Direction Labeled by the direction from which they blow
Ex: winds blowing from the Southeast.
Tool: Wind Vane

14. Wind Speed
Anemometer
Measures how fast wind is blowing

15. Global Winds
The atmosphere balances itself by acting as a giant heat-transferring system
Moves warm air to the poles and cool air towards the equator

16. Global Winds Trade winds Westerlies Polar easterlies Polar front
Two belts of winds that blow almost constantly from east to west
Westerlies
Dominate west to east motion of the atmosphere
(Jet Stream occurs here)
Polar easterlies
Winds that blow east to west
Polar front
Interaction of warm and cool air masses produces a stormy belt