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
CirroHigh clouds
AltoMiddle Clouds
StratoLow clouds
fog
Cloud Types
Precipitation
RAIN
SNOW
SLEET
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