Unit 6: Properties of the Atmosphere
Atmospheric Variables
Do Now: What is Weather? ___________________
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What are the major components of the atmosphere?
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ESRT
What is the structure of the atmosphere?
Complete Worksheet
List and define the conditions of the atmosphere that interest
meteorologists the most. (Review book Chapter 6)
Temperature:___________________________________________
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Unit 6-7: Properties of the Atmosphere (cont.)
The Station Model
Station Model Hot Tips:
1. Sky cover “pies” sweep quarters of the circle
like a clock’s hand.
2. The Wind flag staff always points into the wind
or the wind blows down the flag staff into the
circle.
3. Wind speed short feather = 5 knots ( 2kts)
4. If pressure trend is negative, three hours ago,
the pressure was higher
a) current pressure and pressure trend
will always be to tenth (no decimals on
the station model)
5. Maximum pressure range: 960mb to 1050mb
More Helpful Hints:
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Unit 6: Properties of the Atmosphere
Atmospheric Pressure
Do Now:
Pressure: The force caused by the weight of the
atmosphere on a given surface area. The units for air
pressure can be expressed as:
mb ______________________
lbs/in2 ____________________
Inches or cm of (Hg)________________
Demo: Draw arrows on the following diagram to
represent the confining pressure on the surface of the
can. Let arrow length represent the strength of the
pressure field.
Equal inside and out
Air removed, higher pressure outside
Pressure is affected by air density directly.
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Unit 6: Properties of the Atmosphere
Atmospheric Moisture
Do Now: Use the following words to indicate the
processes in the simplified water cycle diagram below.
Remember – clouds are made of liquid water
Condensation
Stratosphere
Word Bank
Precipitation
Evaporation
Energy Source
Water Source
1. _________________
2. _________________
3. _________________
4. _________________
5. _________________
1. Sources of Atmospheric Moisture:
a) Evaporation (Vaporization) = liquid  gas
b) Transpiration – process by which
photosynthetic organisms release water vapor
(mostly plants and algae)
c) Evapotranspiration – combination of a & b
d) The oceans cover >70% of the Earth’s surface
and are the primary source of atmospheric
moisture.
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2. Energy is absorbed into the atmosphere when water
changes from a liquid to a gas.
Amount of energy gained (by the atmosphere) during
vaporization =___________cal/g - see ESRT page 1
Energy source for vaporization: _________________
3. Factors Affecting Evaporation Rate
a) available energy (Sun or Heat)
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b) surface area exposed
(Tumbling, Hanging, Brushing)
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b) air movement
(Wind or Fan)
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c) amount of moisture
already in the air (Humidity)
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Unit 6: Properties of the Atmosphere
Atmospheric Moisture (cont.)
Water Vapor Fact #1: As air temperature increases,
its ability to hold water vapor also increases.
See flask diagrams handout and RB figure 6-11.
Water Vapor Fact #2: Water vapor is less dense
than air, so “humid” air is generally less dense than
dry air. (Remember, less dense = less pressure)
4. Absolute Humidity – the volume of water vapor in
a given volume of air Ex: 3 ml/m3
5. Relative Humidity – the ratio of the amount of
water vapor in the air compared to the maximum
amount the air can hold at that temperature, or “How
full of moisture the air is”. The total amount of WV
the air can hold is known as its capacity.
 Rh is reported as a percent (%)
 Rh of 100% is considered saturated
Air temperature and Rh are ____________ related.
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Unit 6: Properties of the Atmosphere
Atmospheric Moisture (cont.)
The temperature at which air becomes saturated is
called the dewpoint temperature (DPT).
Relative humidity can be measured by an instrument called a hygrometer. The simplest
hygrometer -a sling psychrometer - consists of two thermometers mounted together with a
handle attached on a chain. Of course, those are expensive so YOU get some cheap flimsy
ones. One thermometer is ordinary and is called the dry bulb thermometer, the other has a
wet cloth wick over its bulb and is called a wet-bulb thermometer.
When a reading is to be taken, the dry bulb is read first, then the wet bulb
thermometer with its wick is dipped in water and then the instrument is whirled around
and usually flies apart. During the whirling, the water evaporates from the wick, cooling
the wet-bulb thermometer. Then the temperatures of the wet bulb is read. If the
surrounding air is dry, more moisture evaporates from the wick, cooling the wet-bulb
thermometer more so there is a greater difference between the temperatures of the two
thermometers. If the surrounding air is holding as much moisture as possible - if the
relative humidity is 100% - there is no difference between the two temperatures.
Meteorologists have worked out charts of these differences for each degree of temperature
so that the observer can find relative humidity easily. See ESRT.
Indoors:
Outdoors:
Dry Bulb__________
Dry Bulb__________
Wet Bulb__________
Wet Bulb__________
Rh________________
Rh________________
DPT______________
DPT_______________
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Unit 6: Properties of the Atmosphere
Atmospheric Pressure
Factors Affecting Air Pressure:
Humidity vs. Pressure
Temperature vs. Pressure
Air Density vs. Pressure
Altitude vs. Pressure
1. Air with high density weighs more causing __________ pressure. Air density and
pressure are _________ related.
2. As the amount of water vapor in the air _________________ the air density
______________ causing the pressure to __________________. Humid air is ________
dense than dry air causing _______pressure.
3. As the air temperature increases, the density of the air _____________ causing the air
pressure to __________________. Warm air is _________ dense than cold air.
4. As altitude increases, the pressure __________________ (see ______ chart page ___).
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Unit 6: Properties of the Atmosphere
Adiabatic Cooling/Heating
Adiabatic Cooling and Heating:
a) As a gas expands, its
temperature decreases.
b) As a gas compresses, its
temperature __________.
Energy is neither added nor
removed; during expansion, the
heat energy is spread out over a
larger volume resulting in a lower measured
temperature.
As air rises, it expands and cools.
If the air cools below its dewpoint,
condensation will occur. This
happens at a particular elevation,
depending upon the air temperature
and humidity.
As DRY air rises, its temp decreases about
5.5F per 1000 ft. This is known as the Dry
Adiabatic Lapse Rate. As SATURATED (wet)
air rises, it cools at 3.5F per 1000 ft. This
difference results from water vapor in the
saturated air condensing. As the vapor
condenses, it releases _____cal/g of heat into
the air causing the WET adiabatic lapse rate to
be less (3.5F).
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Water vapor requires a surface for condensation.
This surface is called a condensation nucleus.
Shade in the flask
containing
condensation
Flask, room
temperature
Flask, cooling on an
ice cube, no
condensation nuclei
Flask, cooling on an
ice cube, WITH
condensation nuclei
Explain this drawing of the Orographic Effect:
Why is rain only falling on one side of this
mountain?
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Summary: How do clouds form?
Warm air _________ and expands. As the air expands it
____________. If the air cools to it’s ___________temperature,
the air becomes saturated with ____________ ____________.
More cooling results in ________________, creating a cloud.
Clouds are made of _____________ (phase) water.
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Unit 6: Properties of the Atmosphere
Atmospheric Pressure/Wind
Wind – the horizontal movement of air parallel to the
Earth’s surface (vector quantity).
1. _________________ differences between two
places cause density differences in the air.
2. Density differences cause air pressure
differences (see notes pages 3 & 8)
3. Pressure differences cause air to move
horizontally from Higher to Lower pressure.
4. Winds are named by the direction they come
_________________!
Pressure Gradient – difference in air pressure over a
certain ________. Write formula here:
1. The closer the isobars are
together, the stronger the
pressure gradient force
resulting in _____________
wind speeds. (see handout)
The Coriolis effect deflects winds to
the __________ in the northern
hemisphere, and to the _______ in
the __________ _____________.
The Coriolis effect results from
Earth’s rotation.
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Unit 6: Properties of the Atmosphere
Circulation In the Atmosphere
1. Convergence – winds come together and rise –
caused by LOW pressure
2. Divergence – air is sinking and spreads out at
the surface – caused by HIGH pressure.
H
L
High pressure circulation is clockwise and diverging. Low
pressure circulation is _________________ and ______________.
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Unit 6: Properties of the Atmosphere
Circulation In the Atmosphere
1. Atmospheric circulation distributes the sun’s
energy by the process of convection. Convection
cells may exist on a local and global scale.
2. Local Winds – see “Land and Sea Breezes” handout
3. Global/Planetary winds – a series of wind belts in
the troposphere blowing horizontally away from
areas of divergence (____pressure) toward areas of
convergence (_____pressure). See ESRT page ____.
These winds curve to the ________ in the _______
__________________ and to the ___________ in the
_________ ___________________ due to the
___________ ___________.
Complete “Global Wind Patterns” handout.
Simple model of
circulation assuming
no axial tilt, no rotation
(Coriolis), and all
surface materials equal.
A more realistic model of actual
circulation. Draw arrows
depicting the “Hadley Cells”
around the question marks.
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4. Surface Ocean Currents -movement of surface
ocean water caused directly by winds transferring
some of their energy to the water. __________ are/is
also caused by the wind on the water’s surface.
Sea ESRT.
Summary Regents Questions:
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