Water in the Air Chapter 3 Section 1 pg. 76

The Water Cycle  The continuous movement of water from sources on Earth’s surface—such as lakes, oceans, and plants—into the air onto and over land, into ground, and back to the surface.

The Water Cycle

   resources/water-cycle-in-a-bag.html resources/water-cycle-in-a-bag.html

The Water Cycle 1. Evaporation  Occurs when liquid water changes into water vapor 2. Condensation  Occurs when water vapor cools and changes from a gas to a liquid. Clouds form by the process.

The Water Cycle 3. Precipitation  Occurs when rain, snow, sleet, or hail falls from the clouds onto Earth’s surface. 4. Runoff  Is water, usually from precipitation, that flows across land and collects in rivers, streams, and eventually the ocean.

Humidity  The amount of water vapor in the air  As water evaporates from lakes, oceans, and plants, it becomes water vapor, or moisture in the air  The air’s ability to hold water vapor changes as the temperature of the increases

Relative Humidity  Amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature  When air holds ALL it can at a certain temperature it is said the be saturated 

Factors Affecting Relative Humidity  2 factors  Amount of water vapor and temperature  Relative humidity decreases as the temperature rises and increases as the temperature drops**********  Psychrometer  tool used to measure relative humidity

Condensation

 The process by which a gas, such as water vapor, becomes a liquid  Before condensation can happen the air must be saturated, which means that the air must have a relative humidity of 100%  Occurs when saturated air cools

Dew Point  The temperature at which a gas condenses into a liquid.  At its dew point, air is saturated  Before water vapor can condense, though, it must have a surface to condense on.

Clouds  A collection of millions of tiny water droplets or ice crystals  Classified by form and altitude  Form as warm air rises and cools  As the cool air rises it becomes saturated  When the air is saturated, the water vapor changes to a liquid or a solid, depending on the air temperature. If temps are above freezing, water vapor condenses on small particles in the air and forms tiny water droplets. At temps below freezing, water vapor changes to a solid to form ice crystals.

Cumulus Clouds  Puffy, white clouds that tend to have flat bottoms  Form when warm air rises  Generally indicate fair weather, but when they get larger, they produce thunderstorms  Thunderstorms come from a kind of cumulus could called a cumulonimbus cloud  Clouds that have that include –nimbus or nimbo- are likely to produce precipitation

Stratus Clouds  Form in layers  Cover large areas of they sky and block out the sun  Caused by gentle lifting of a large body of air into the atmosphere

Stratus Clouds  Nimbostratus clouds are dark stratus clouds that usually produce light to heavy, continuous rain  Fog is stratus cloud that has formed near the ground

Cirrus Clouds  Thin feathery, white clouds found at high altitudes  Form when the wind is strong  If they get thicker, cirrus clouds indicate that a change in the weather is coming.

Clouds and Altitude  Prefix cirro-  Used to describe clouds that form at high altitudes  Prefix alto-  Clouds that form at middle altitudes  Clouds that form at low altitudes do not have a specific prefix to describe them.