2.3 Most clouds form as air rises and cools.
Review: Use the internet.
- Does wind move horizontally or vertically?
- Does warm air rise or sink?
- Does air move from low to high pressure areas or from high to low?
- What does the Coriolis effect cause in relation to earth's weather?
Water is always present in the atmosphere. When temperature changes, water changes form.
- Evaporation: the process by which a liquid changes into a gas.
- Condensation: is the process by which a gas, such as water vapor changes into a liquid.
- Precipitation: Any type of liquid or solid water that falls to Earth's surface.
Humidity and Relative Humidity
Humidity is the amount of water vapor in the air. Humidity varies from place to place and from time to time. On hot sunny days with high humidity it is uncomfortable to be outside because the water vapor does not evaporate from your skin because there is too much water condensing and not enough evaporating. Saturation happens when the rate of evaporation and condensation are equal. The amount of water in the air at saturation depends on the temperature of the air. The warmer air is, the more water vapor it takes to saturate it. Scientists describe the humidity of air in tow different ways.
Humidity is the amount of water vapor in the air. Humidity varies from place to place and from time to time. On hot sunny days with high humidity it is uncomfortable to be outside because the water vapor does not evaporate from your skin because there is too much water condensing and not enough evaporating. Saturation happens when the rate of evaporation and condensation are equal. The amount of water in the air at saturation depends on the temperature of the air. The warmer air is, the more water vapor it takes to saturate it. Scientists describe the humidity of air in tow different ways.
- Relative humidity:
- compares the amount of water vapor in air with the maximum amount of water vapor that can be present at that temperature. For example, air with 50 percent relative humidity has half the amount of water needed for saturation. If the amount of water vapor in air stays the same, relative humidity will decrease as the air heats up and increase as the air cools.
- Dew Point:
- is the temperature at which air with a given amount of water vapor will reach saturation. For example, air with a dew point of 79 degrees will become saturated if it cools to 78.8 degrees. The higher the dew point of air, the more water vapor the air contains.
Clouds are caused by warm air rising in the atmosphere as it cools. Location affects what clouds are made of. Clouds at high levels in the troposphere are made of ice crystals. Clouds closer to earth's surface are make of water droplets.
There are 3 main types of clouds
Cirrus Clouds:
- Form in very cold air at high altitudes
- made of ice crystals
- wispy or feathery appearance
- usually seen fair weather
- puffy and white with darker bases
- usually appear in daytime in fair weather
- can produce short rain showers
- make the whole sky look gray
- form in layers when air cools over a large area
- can completely block out sun (nov and dec in wisco)
- is a cloud that rests on the ground or a body water
- forms when surface is colder than the area above it
- Fog kills close to 700 people a year in automobile accidents.
Types of Precipitation:
- Rain: we know
- Freezing Rain: (freezes when it hits the ground) can cover roads and sidewalks and cause trees to fall
- Sleet: when rains freezes before it hits the ground.
- Snow: we know
- Hail: Lumps or balls of ice that fall from clouds. During a thunderstorm violent air currents hurl ice pellets around in clouds. Large hailstones can cause large amounts of property damage. The biggest hail stone in u.s. history was 1.7 pounds and as wide as a DVD.