Chapter 16.1

Water in the Air

Team Work!

• In you team of 4 people…diagram the water cycle in your composition book. (section 16.1)

• Label each part of the water cycle

• Define each label as you go

Water Cycle

• Definition:

–The continuous movement of water from Earth’s surface (oceans and rivers) into the air (atmosphere), onto and over the land, into the ground, and back to the surface.

Illustration

http://en.wikipedia.org/wiki/Image:Water_cycle.png

Evaporation

• Water from the Earth’s surface to the air, the process by which water changes from a liquid (water) to a gas (water vapor).

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/evap.rxml

Transpiration

• Evaporation of water into the Atmosphere from plants.

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/trsp.rxml

Condensation

• Process by which water changes from a gas (water vapor) into a liquid (water).

• Cloud Formation.

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/cond/home.rxml

Precipitation

• Process by which water moves from the Atmosphere (clouds) to the Earth’s surface.

• May be in the form of rain, sleet, snow, or hail.

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/prcp.rxml

Runoff

• The movement of water that flows across land and collects in rivers and streams and eventually ends up in the oceans.

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/run.rxml

Putting it all together

• The Water Cycle

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/smry.rxml

The Water Cycle

Humidity

• The amount of water vapor in the air

• Relative Humidity=The amount of water vapor in the air

The maximum amount of water vapor the air can hold at a given temperature.

Relative Humidity

• This graph shows that as air gets warmer, the amount of water vapor that the air can hold increases.

• When air hold all of the water vapor that it can at any given temperature, it is said to be saturated.

• Saturated air has a relative humidity of 100%.

Factors Affecting Relative Humidity

• 1) Amount of Water Vapor

• 2) Temperature

• Relative Humidity changes if either one (or both) changes

Measuring Relative Humidity• Psychrometer

– Instrument used to measure relative humidity. – Made of wet-bulb and dry-bulb thermometers.

http://www.usatoday.com/weather/wsling.htm

Sling Psychrometer

Determining Relative Humidity• Once you have both thermometer readings, you

use the chart to find the relative humidity.

Dew Point

• The temperature at which the air becomes completely saturated= 100%

• Temperature of air must cool to become saturated

• Thermal Energy travels from hot to cold

• At this temperature gas → liquid – (Water vapor condenses into water)

Clouds

• Definition– A collection of small water droplets or ice

crystals suspended in the air, which forms when air is cooled and condensation occurs.

• Clouds are classified by form and altitude.

Convective Cooling…How to make a cloud!

• 1. Air rises

• 2. Molecules move apart

• 3. Uses potential energy

• 4. Lowers temperature

Condensation Level

• The level in the atmosphere where condensation occurs.

• The temperature is lower than the dew point of the air, therefore condensation occurs.

• The base of the cloud is the level in the atmosphere where it’s cold enough to condense!

Cumulus Clouds

• Means “heap”• Puffy, white clouds with flat bottoms• Usually indicate fair weather

http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/fair_cumulus.rxml?hret=/guides/mtr/cld/cldtyp/home.rxml

Cumulonimbus Clouds

• Nimbus means “rain”• Thunderstorm clouds• Tall, dense, usually dark

http://www.answers.com/topic/cumulonimbus-cloud-1

Stratus Clouds

• Means “layered”- form in layers• Covers large area of the sky• May bring dull and grey weather

http://www.ace.mmu.ac.uk/eae/Weather/Older/Stratus_Clouds.html

Cirrus Clouds

• Means “curl of hair”• High level clouds• Made of ice crystals

http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cirrus.rxml?hret=/guides/mtr/cld/cldtyp/home.rxml

Altitude

Cirro- Alto- Strato- High clouds Middle Clouds Low clouds

fog

Cloud Types

PrecipitationRAIN SLEET

SNOW HAIL

Hail

Precipitation

• Rain 0.5 – 5 mm diameter

• Drizzle < 0.5 mm diameter

• Snow = ice particles

• Sleet = ice pellets form when rain falls through a layer of freezing air

• Hail = solid lumps of ice form in cumulonimbus clouds