Download Lesson 2

AOSC 200
Lesson 2
Other important Gases
• Methane - CH4
• Is produced whenever plant material decays below water, e.g.
in marshes and rice paddies.
• Is a greenhouse gas. Has a long lifetime in the Troposphere but
breaks down in the Stratosphere to form water.
• Cholofluorocarbons - scientific name for the Freons.
• Are greenhouse gases
• Have a long lifetime in the Troposphere but break down in the
Stratosphere to releases chlorine. Responsible for the Ozone
Hole.
• Emissions were banned as a result of the Montreal Protocol.
Fig. 1-7, p. 9
Fig. 1-8, p. 10
Fig. 1-9, p. 11
Aerosols
• PARTICLES SUSPENDED IN THE ATMOSPHERE
• DIAMETERS MEASURED IN MICRONS – ONE
MILLIONETH OF A METER.
• CAN MODIFY THE AMOUNT OF SOLAR ENERGY
THAT REACHES THE SURFACE.
• CAN ACT AS CONDENSATION NUCLEI FOR
CLOUD DROPLETS.
• PRIMARY SOURCES:
• SEA SALT SPRAY
• WIND EROSION
• VOLCANOES
• FIRES
• HUMAN ACTIVITY
Fig. 1-10, p. 11
Smoke from Forest
Fires along the
coast of California.
Fig. 1-11, p. 12
Smoke from
Forest Fire
in New
Mexico
Fig. 1.11
Toricello
• Filled a glass tube sealed at one end
• He then inverted the tube in a bowl of mercury
• Found that the mercury did not flow out of the
tube but remained in the tube, and that the
height of the mercury column was constant each
time he tried the experiment.
• He reasoned that the air was keeping the
mercury in the column by pressing down on the
bowl of mercury.
Fig. 1.13
Fig. 1-13, p. 15
Fig. 1.12
Atmospheric Pressure
• PRESSURE AT A POINT IS THE WEIGHT OF AIR
ABOVE THAT POINT
• A COLUMN OF AIR AT THE SURFACE WEIGHS
SLIGHTLY MORE THAN 1 KILOGRAM PER SQUARE
CENTIMETER
• IN STILL AIR, TWO FACTORS DETERMINE THE
PRESSURE – TEMPERATURE AND DENSITY
• IDEAL GAS LAW
• PRESSURE =
DENSITY.TIMES.TEMPERATURE.TIMES.CONSTANT
• PRESSURE CHANGES WITH ALTITUDE
Fig. 1-14, p. 17
1. Troposphere- literally means region where air “turns over”
-temperature usually decreases (on average ~6.5°C/km) with altitude
Tropopause
2. Stratosphere- layer above the tropopause, little mixing occurs in
the stratosphere, unlike the troposphere, where “turbulent mixing”
is common
Stratopause
3. Mesosphere- defined as the region where temperature again
decreases with height.
Mesopause
4. Thermosphere- region with very little of the atmosphere’s mass.
high energy radiation received by the thermosphere (high
temperatures experienced). A small density of molecules (not
much “heat” would be felt).
When the atmosphere moves it tends to move
along constant pressure lines (isobars) and not
along constant altitude lines.
In meteorology it is helpful to refer to altitude
as a certain pressure value rather than a height.
850 mb  1500
700 mb  3000
500 mb  5500
300 mb  9000
m
m
m
m
(5000 ft)
(10,000 ft)
(18000)
(30,000)
FRONTS
• You will often hear TV meteorologists refer to
cold and warm fronts when describing the
weather.
• Fronts are regions where cold and warm air
masses meet.
• This is the region where most of the ‘weather’ is
generated.
• We identifiy four main classes of fronts, warm,
cold, stationary, occluded.
• Each front has an unique symbol on weather
maps.
Fig. 1-15, p. 18
Warm Front
Fig. 9.13
Cold front
Fig. 9.15
Weather Symbols
Fig. 1-17, p. 21
Detailed weather symbols
(1) Direction of arrow into the circle gives the wind direction. Number of barbs
on the arrow gives the wind speed. Full barb = 10 miles per hour, half barb=5.
(2) Sign, middle left, gives the type of precipitation. In the top left symbol the
sign is fot thunder. In the bottom left it stands for steady rain.
(3) Shading in inner circle gives the cloud fraction.
(4) Top number on left is the temperature, bottom number the dew point
Weather symbols
• The numbers at top right of each symbol
represent the pressure in millibars (mb)
• The pressure seldom drops below 950 mb and
seldom gets above 1049 mb
• In the days of teletype the object was to shorten
the amount of information sent.
• So if I say the pressure was 98 then the receiver
could assume that I meant 998. And if I sent 14
then 1014 was assumed.
• To further confuse the issue it was decided to
sent the tenth of a mb. So now if I sent 998 I
meant 999.8. Similarly 117 means 1011.7.