1. Water and Wind in Earth’s Atmosphere

2. Winds
What causes this?

3. What is Wind?
Wind is the horizontal movement of air from an area of high pressure to an area of low pressure.
Larger difference in pressure = stronger wind
Differences in air pressure are caused by unequal heating in the atmosphere.
As cooler, denser air sinks, warm, less dense air is forced to rise.

4. Measuring Wind Winds are described by their direction and speed:
A wind vane determines wind direction.
An anemometer measures wind speed.
The name of the wind tells you the direction it is blowing from
a west wind blows from the west toward the east.

5. Local Winds
Local winds are winds that blow over short distances and are caused by the unequal heating of Earth’s surface within a small area.
A sea breeze is a local wind that blows from a lake or ocean toward land
Since land is heated faster than a body of water, the air above the land gets warmer and rises, allowing cooler air from the ocean to move underneath the warm air.

8. Humidity Humidity: how much H2O vapor is in the air.
What can hold more water?
warm or cold air?
Relative humidity: the % of water vapor in the air compared to the maximum amount of water vapor the air can hold at a given temperature
Psychrometer: device used to measure relative humidity, by comparing a “dry” temperature and a “wet” temperature.

10. Cloud Formation
Clouds form when H2O vapor condenses into liquid water or ice crystals.
2 conditions needed:
1. cooling of the air
2. particles in the air for H2O vapor to condense around

12. Clouds are classified by:
Shape
Cumulus – puffy
Cirrus – thin, wispy
Stratus – flat, layered
B. Altitude/weather
1. Cirro – high
2. Alto – mid-level
3. Nimbo – rain producing

13. Guess the Clouds!