Transcript The distribution of the gas phase of water on the Earth

Chemistry Unit
Properties of Water and
their Relationship to
Weather and Climate
The Three Phases of Water
Solid: Ice
Liquid: Water
Gas: Water Vapor
When water changes phases, a large amount of energy
is absorbed or released.
What causes water to change phase?
Theoretically liquid water
turns into…
• Ice at 0oC
– When water turns into ice
it gives out a large
amount of energy
• Vapor at 100oC
– When water turns into
vapor it absorbs a very
large amount of energy
What causes water to change phase?
0n the Earth water can turn into the gas phase when the
temperature is much lower than 100oC.
• Evaporation can happen at any temperature, but as the
temperature increases evaporation increases.
• Evaporation also relates to the humidity of the air and the
availability of water on the ground. If it is over the ocean, then
there is plenty of water to evaporate.
• Humidity: the amount of water vapor in the air. It indicates
the likelihood of
– Precipitation
– Dew
– Fog
• 100% humidity means that the air is fully saturated with water
vapor.
How are the different phases of
water distributed on the Earth?
• Where are the liquid
phases of water?
100
90
– In the oceans (mostly)
• Where are the gas phases
of water?
50
Percent (%) on Earth
• Where are the solid phases
of water?
80
70
• 98.299% of water is liquid,
1.7% solid, and only 0.001%
as gas.
20
– In ice
– In the air
60
40
30
10
0
Gas
Liquid
Solid
Phases of Water on Earth
The distribution of the solid phase of water on
the Earth.
• Icebergs and other sea
ice floating on the ocean
• Ice sheets on land
– Greenland
– Antarctica
– Alaska
• Mountain glaciers
The distribution of the solid phase of water on
the Earth.
• Icebergs and other sea
ice floating on the ocean
• Ice sheets on land
– Greenland
– Antarctica
– Alaska
• Mountain glaciers
The distribution of the solid phase of water on
the Earth.
• Icebergs and other sea
ice floating on the ocean
• Ice sheets on land
– Greenland
– Antarctica
– Alaska
• Mountain glaciers
The distribution of the liquid phase of water on
the Earth.
By far most of
the water is in
the ocean –
96.5%!
The distribution of the liquid phase of water on
the Earth – the oceans.
• Ocean water contains dissolved minerals – “salt”
– Salt water is denser than freshwater because of the
dissolved salts -- the higher the salinity (more salt in the
water) the greater the density.
• Salt water freezes at a lower temperature than fresh
water.
– The higher the salinity the lower the freezing/melting
point.
• Salt water boils at a higher temperature than fresh
water
– The higher the salinity the higher the boiling/condensation
point.
The distribution of the liquid phase of water on
the Earth – the oceans.
• Density of seawater
– Increases with increasing salinity and decreasing
temperature.
– Increases with increasing pressure – pressure increases
with depth.
• Ocean layered according to density
– Halocline: Salinity gradient
– Thermocline: Temperature gradient
– Pycnocline: Density gradient
The distribution of the liquid phase of water on
the Earth – the oceans
• Halocline: zone of rapid
change of salinity with
depth.
• Dense water is heavy and
sinks below less dense
layers.
The distribution of the liquid phase of water on
the Earth – the oceans
• Thermocline: zone in
which temperature
decreases rapidly with
depth.
• 3 zones in ocean based on
temperature variation:
– Surface zone
– Thermocline
– Deep zone
• Notice that temperature in
the deep ocean is similar in
low and high latitudes.
• Changes in the thermocline
(e.g., the slope of it) can
have a significant influence
on global climate.
The distribution of the liquid phase of water on
the Earth – the oceans
• Pycnocline: zone in
which density increases
rapidly with depth.
– Thermocline & halocline
together make the
pycnocline.
The distribution of the gas phase of water on the
Earth – the air.
• Water vapor in the air is called humidity.
• Humidity: the amount of water vapor in the air
• Water vapor content (humidity) decreases with
increasing altitude.
• As the temperature of the air decreases the amount
of water vapor (humidity) that can be held in the air
decreases.
The distribution of the gas phase of water on the
Earth – the air.
How is water vapor
distributed by
latitude?
These different “air
masses” move around
and cause weather
phenomena, such as
cold fronts and warm
fronts.
The distribution of the gas phase of water on the
Earth – the air.
Temperature, density,
and pressure differences
in the atmosphere:
• Temperature varies as
altitude increases.
• Density decreases as
altitude increases.
• Pressure decreases as
altitude increases.
The distribution of the gas phase of water on the
Earth – the air.
What happens to the gas phase when the vapor rises
through the atmosphere and cools down?
• The water vapor will condense creating clouds
• When the clouds become supersaturated (have a
humidity higher than 100%) they form rain (or snow
depending on the air temperature).
The distribution of the gas phase of water on the
Earth – the air.
• The distribution and
movement of air with
different temperature
and water vapor content
have significant control
over weather conditions.
• For example: What makes
a cold front?
– Pressure differential
– Temperature difference
The distribution of solid, liquid, and gas phases
of water affect weather and climate.
• The amount and distribution of different phases of
water largely controls the earths weather and
climate:
– Short-term changes, e.g., in days to months, cause
different weather conditions.
– Long-term changes, e.g., in 10s to 100s of years, cause
climate change.
How does the distribution of solid, liquid, and gas
phases of water affect weather and climate?
Let’s look at the overall
budget of water on
earth.
– Solid: 1.7%
– Liquid: 98.299%
– Gas: 0.001%
90
80
Percent (%) on Earth
• Percentage of the
phases of water
found on Earth
100
70
60
50
40
30
20
10
0
Gas
Liquid
Solid
Phases of Water on Earth
How does the distribution of solid, liquid, and gas
phases of water affect weather and climate?
What if this particular balance changes??
• Assume 1.7% in ice now. What if 2.7% of the water is
in ice? Then there is 1% less water in the ocean.
– That means sea level is much lower.
• So what if 0.7% of water is in ice?
– That means sea level is much higher.
How does the distribution of solid, liquid, and gas
phases of water affect weather and climate?
• Let’s think about what can change the water budget:
– What would increase the amount of solid water on the
earth?
– What would increase the amount of liquid water on the
earth?
How does the distribution of solid, liquid, and gas
phases of water affect weather and climate?