Water in the Atmosphere

1
Water in the Atmosphere

• Earth Science/Geology
• Mr. Traeger

2
We must understand the properties of water in
order to understand how it behaves in the
atmosphere.
The structure of water looks like Mickey Mouse.
Two Hydrogens and One Oxygen bond to make H2O.
3
We must understand the properties of water in
order to understand how it behaves in the
atmosphere.
Water molecules bond in hydrogen bonding where
the positive hydrogen bonds with the negative
oxygen.
4
This bonding of molecules allows for changes of
state of water.
Water molecules bond in hydrogen bonding where
the positive hydrogen bonds with the negative
oxygen.
5
Water is the only substance that commonly exists
in all three states of matter. This is solid,
liquid, and gas (Spaulding, 390).
6
Here are the states of water. See page 391 in
your book for a better diagram. Note where heat
is released and where heat is absorbed.
7
Remember when we heated water from ice to water
to steam? This is the graph that we did in class.
8
Notice how water goes through phase changes from
solid (ice) to liquid (water) to gas (water
vapor).
9
Water melts at zero degrees Celsius and boils at
100 degrees Celsius.
10
The change of state of water contributes to the
Water Cycle, the unending circulation of water
throughout the planet. See page 13 in your book
for more details.
11
Humidity
The City of Atlanta, Georgia has very high
humidity in the summertime! What does it feel
like when it is hot and humid?
12
What is Specific Humidity?
13
Specific Humidity is the actual amount of water
vapor in the air. It does not depend on
temperature. It is expressed in grams of water
per kilograms of air.
14
What is Relative Humidity?
15
Relative Humidity is the actual amount of water
vapor in the air compared to the maximum amount
of water vapor the air can hold.
16
Relative humidity is expressed in percentage.
17
If the air has a specific humidity of 50 g/kg and
the air will hold 100 g/kg, what is the relative
humidity?
18
50 / 100 0.50.5 X 100 50So the relative
humidity is 50.
19
If the air has a relative humidity of 100, what
will happen?
20
Clouds or fog will form!
21
Go here to see the different types of clouds. Go
here to see even more clouds!
22
Multiple cloud layers as seen from the air
climbing out of Minneapolis, MN on 12/31/05.
Stratus clouds below and cirrostratus/cirrocumulus
clouds above
23
Clouds or fog will form when the temperature and
dew point are the same.
24
But in order for clouds or fog to form, small
dust particles called condensation nuclei are
required!
25
Fog is a cloud at or near the ground.
26
Radiation fog is formed when moist air near the
ground is cooled to dew point on a cold, clear
night.
27
Advection fog is formed when warm, moist air
moves over a cold ocean surface. The fog off of
our coast is advection fog.
28
Cloud FormationA cloud will form at the
elevation where the temperature and dew point are
the same.
29
Cloud StabilityFlat clouds like stratus clouds
are stable. This means that the center of the
cloud is colder or at the same temperature as
outside.
30
Cloud StabilityClouds with vertical growth are
said to be unstable, which means the center of
the cloud is warmer than the air outside. Warm
air will rise.
31
Cloud StabilityInstability in a cumulonimbus
cloud leads to thunderstorms, lightning, hail,
flooding, wind, and tornadoes.
32
Lapse ratesA lapse rate is how fast air cools
with altitude. You can use this value to
calculate the altitude at which a cloud will form.
33
Lapse ratesDry air cools at a rate of around
10C per every 1000 meters.
34
Lapse ratesMoist air cools at an average of 7C
per every 1000 meters.
35
Cloud formationA cloud will form when the
temperature and dew point temperature are the
same. See an animation of cloud formation.
36
Cloud formation problem 1The temperature at the
surface is 20C and the dew point is 10C.
Assuming that the dew point temperature does not
decrease (which it does), what altitude will the
cloud form at? Assume that there is dry air
between the surface and the cloud.
37
Cloud formation problem 1Answer20 -10 10
Dry air cools 10 C for every 1000 meters.So,
the cloud will form at 1000 meters!
38
Cloud formation problem 2The temperature at the
surface is 30C and the dew point is 5C.
Assuming that the dew point temperature does not
decrease (which it does), what altitude will the
cloud form at? Assume that there is dry air
between the surface and the cloud.
39
Cloud formation problem 2Answer30 -5 25
Dry air cools 10 C for every 1000 meters.So,
the cloud will form at 2500 meters!
40
Precipitation
41
Precipitationforms when clouds become saturated
with water.
42
There are different kinds of precipitation.
43
Rain droplets grow by collision with other water
droplets.
44
Drizzle is a light rain where the drops are small.
45
Ice crystals or super cooled droplets usually
form in clouds.
46
If the flake does not melt before hitting the
ground, we call this snow.
47
Sleet are raindrops that re-freeze as they fall
through the sky.
48
Freezing rain is when rain freezes instantly when
hitting the ground.
49
Hail is frozen ice that grows in updrafts and
downdrafts of thunderstorms. It finally becomes
too heavy and falls to the ground.
50
Precipitation is measured using a rain gauge.
Snow must be melted to determine its water
content.
51
Where does precipitation occur?
52
Precipitation occurs where moist air rises and
cools.
53
There is little or no precipitation where air
sinks and warms.
54
The rain shadow effect determines precipitation
amounts. Go here for another rain shadow
animation.
55
The rain shadow effect seen from the air. Picture
taken on 12/31/05 on approach into LAX. Mt. San
Jacinto and Palm Springs are in the distance.
56
The rain shadow effect as seen from visible and
infrared satellite images taken on May 30, 2007.
Notice the unstable cloud development
(cumulonimbus clouds) over the Sierra Nevada
Mountains. Also notice the stable marine layer
(stratus clouds) near the coast.
Infrared Image
Visible Image
57
Average Precipitation in California
58
Dry areas occur on the east (leeward) side of
mountains. Wet areas occur on the west (windward)
side of mountains.
59
The Northern part of the state gets more
precipitation because more low pressure storms go
through that area. Central and Southern
California are usually under the influence of
high pressure and clear weather. See pages
422-425 for more details on pressure patterns.
60
Water Resources Owens ValleyThe Los Angeles
Aqueduct System
61
Water Resources Colorado RiverThe Los Angeles
Aqueduct System
62
Water Resources Groundwater
63
Water Resources Local streams and reservoirs
64
Population Growth in the Imperial Valley Will
our water resources be able to support the
projected population growth?Red areas mean more
and healthier crops.
June 9,1973
June 30,1992
65
No more water left over for Mexico? Compare the
crop health in the U.S. to the crop health just
across the border in Mexico. Can you see the
border?
66
Go here for a water use survey!Go here for water
science for schools!