Atmospheric Conditions and the Water Cycle

1. Atmospheric Conditions and the Water Cycle

2. Atmospheric Conditions Theatmosphere of Earth is a layer of gases surrounding the planet Earth

3. Atmospheric Conditions • atmospheric condition - the atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation • Weather is the state of theatmosphere at a given time and place.

4. How Clouds Form • Water vapor • Cool air • Dust particles

5. How Clouds Form • Water vapor When water is heated by the sun it evaporates and becomes water vapor

6. How Clouds Form • Cool air When temperatures or pressures decrease, the air cannot hold as much water. When air is cold the water vapor begins to condense and form clouds.

7. How Clouds Form • Dust particles (Cloud Condensation Nuclei) Clean air (without any dust or particles) will not produce clouds. This dust comes from sources such as volcanoes, cars, sea spray from the ocean, and fires.

8. Humidity • Humidity is the amount of water vapor in the air. • Warm air can hold more water vapor than cold air • High humidity makes people feel hotter outside in the summer because it reduces the effectiveness of sweating to cool the body by reducing the evaporation of perspiration from the skin.

9. Evaporation Factors that effect the rate of evaporation • Temperature: Warm temperatures cause water it evaporate more quickly • Wind: Water will evaporate more quickly on a windy day

10. Dew and Frost Formation • Dew point is the temperature at which water vapor becomes liquid or solid usually forming rain, snow, frost, or dew. • Dew point normally occurs when a mass of air has a relative humidity of 100%. (This means the air is saturated or it has absorbed all of the water it can hold)

11. Dew and Frost Formation • Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening. • If the dew point is above freezing dew will form. • Frost is the solid or frozen deposition of water vapor from saturated air. • If the dew point is below freezing, it is referred to as the frost point.

12. Precipitation • Rain: Non frozen precipitation • Snow: Snowflakes form when tiny supercooled cloud droplets freeze(stay frozen). • Sleet: Ice pellets that form when snowflakes melt and then re-freeze into ice pellets. (freeze then melt and re-freeze) • Hail forms in storm clouds when supercooledwater droplets freeze on contact. The storm's updraft blows the hailstones to the upper part of the cloud ( making the ice pellet bigger each time).(freeze because of storm) • Freezing Rain: When snowflakes melt but do not have time to re-freeze. ( freeze then melt)