Water in the Atmosphere

1. Water in the Atmosphere Chapter 16.4

3. Humidity • A measure of the amount of water vapor in the air • How much water vapor air holds depends on temperature • Warm air holds more water vapor than cold air

4. Relative Humidity • The amount of water vapor in the air compared to the maximum amount of water vapor air can hold at a particular temperature Blue = amount of water in the air Yellow = amount of water air can actually hold

5. Measuring Relative Humidity • R.H. can be measured with a psychrometer

6. To find relative humidity: • Look across from dry-bulb temp • Look down from difference between dry-bulb and wet-bulb temp (dry-wet = difference) • Result is relative humidity

7. Cloud Formation • Clouds form when water vapor in the air condenses to form liquid water or ice crystals • Dew point – the temperature at which condensation begins • Clouds need particles on which to condense (salt, dust, or smoke) • Dew or frost is when water vapor condenses on a surface

8. Clouds Cumulus – fluffy, rounded Cirrus - feathery Nimbus added to cloud type indicates precipitation Stratus – flat layers

9. Cloud Combinations Altostratus- high layered Altocumulus – high puffy Cirrocumulus - fish scales Predicts rain Cumulonimbus – often Produce thunderstorms

10. Let’s Make A Cloud

11. Precipitation • Any form of water that falls from clouds and reaches the surface Rain – water droplet at least 0.5 mm in diameter Sleet – rain that falls through a freezing layer of air and falls to the ground Freezing rain – rain that freezes after hitting the surface

12. Precipitation Snow – water vapor that freezes directly into ice crystals and stays solid all the way to surface Hail – droplet of water that freezes high in a cloud, falls and gathers more moisture in the cloud and is forced upward in the cloud by updrafts to freeze. Falls to ground when it becomes too heavy.