Meteorology and the Atmosphere

1
Meteorology and theAtmosphere

• (Atmosphere History and Composition, Atmosphere
  Structure, Seasons, Heat)

2
Outline

• History Composition of the Atmosphere
• Structure of the Atmosphere
• Density
• Electromagnetic Spectrum
• Layers
• Ozone Layer Hole
• Reasons for the Seasons
• Heat in the Atmosphere (including the Greenhouse
  Effect)

3

• Meteorology is the study of weather and climate.
• weather is local and short-term (changes often)
• climate is regional and long-term (fairly
  constant over time)
• Atmosphere the layer of gases that surrounds
  the Earth.

4
History of the Atmosphere

• At first, there was no atmosphere because Earth
  was too hot and gases could not be held by
  Earths gravity.
• Earth cooled and a primitive atmosphere developed
  (gases from volcanoes and comets).
• Then the modern atmosphere developed. How did
  that happen??

5
Primitive Atmosphere

• From volcanoes and comets.
• Was a reducing atmosphere.
• Consisted of
• Hydrogen (H2)
• Methane (CH4)
• Ammonia (NH3)
• Water (H2O)
• Carbon Monoxide (CO)

6
Modern Atmosphere

• Is an oxidizing atmosphere (has free oxygen
  gas).
• Primitive atmosphere gases got oxidized.
• Consists of
• Nitrogen (N2) 78
• Oxygen (O2) 21
• Carbon Dioxide (CO2) lt 1
• Water (H2O) varies
• Argon (Ar) 1

7
What Happened ?

• What was responsible for changing the Primitive
  Atmosphere to the Modern Atmosphere ?? (Hint
  What produces oxygen gas?)

8
Atmosphere Structure - Density

• Air molecules have mass and weight.
• The more densely packed the air molecules are,
  the higher the air pressure.
• The average air pressure at sea level is almost
  15 pounds per square inch.
• The end of your thumb is about one square inch
  so why isnt your body crushed by all that air
  pressure?

9
(No Transcript)
10
So where do most of the air molecules hang out?
Why?
11

• One half (50) of the air molecules are below 3
  miles (5 km).
• Almost all (99) of the air molecules are below
  18 miles (30 km).
• Why would you need an oxygen mask if you were on
  top of Mt. Everest?

12
Atmosphere Structure - Layers

• In order to understand the layers of the
  atmosphere, first we have to look at the kinds of
  light that reach the Earth the electromagnetic
  spectrum.
• The Sun gives off the light our eyes use to see
  with visible light.
• It also gives off X-rays and Ultraviolet rays,
  which are very dangerous.
• So why dont we get totally fried by X-rays and
  UV?

13
The Electromagnetic Spectrum

• Remember the rainbow ROYGBIV these are the
  colors of visible light our eyes use red light
  has low energy and violet light has high energy.
• There are other kinds of light we cant see
• Lower energy than red Infrared (Heat rays)
• Higher energy than violet Ultraviolet
• Higher energy than Ultraviolet X-rays

14
LOW ENERGY
HIGH
ENERGY
15

• So why dont we get totally fried by X-rays and
  UV?
• There must be something in the atmosphere that
  stops all or most of them.

16
Atmosphere Structure - Layers

• The layers of the atmosphere are
• Troposphere - clouds and planes - to 10 km
• Stratosphere - ozone layer - to 45 km
• Mesosphere - to 80 km
• Thermosphere - to 100 km
• Ionosphere and exosphere (space)
• Complete the graph of the structure of the
  atmosphere from class and the lab activity.

17
(No Transcript)
18
(No Transcript)
19
Ozone in the Atmosphere The Good, The Bad, and
The Ugly

• The Good - Ozone is essential in the upper
  stratosphere (up there) to filter ultraviolet
  radiation that can cause skin cancer.
• The Bad - Ozone is dangerous at ground level
  (down here) because it can cause damage to the
  lungs ozone poisoning. It also erodes plastic,
  rubber and some metals.
• The Ugly The Ozone Hole

20
(No Transcript)
21
The Ozone Hole

• Chlorine from chloro-fluoro-carbons (CFCs) is
  released from discarded or leaky air
  conditioners.
• The chlorine rises to the stratosphere and acts
  as a catalyst to break down ozone.
• Record the equations from class notes.
• The problem is the worst in polar stratospheric
  clouds composed of ice crystals because they
  provide a surface for the reactions.
• Also need sunlight to provide energy for the
  reactions.
• Chlorine ice crystals sunlight Ozone Hole

22
Reasons for the Seasons

• There are three primary causes of the seasons
• Sun angle b/c Earth is a sphere.
• Tilt of Earths axis 23.5 degrees.
• Earths North Pole always points in the same
  direction - parallelism of the axis.

23
1. Sun Angle

• Take notes from class presentation.
• The Suns energy is more concentrated near the
  Equator (direct energy), and more spread out near
  the Poles (indirect energy).
• The result is more intense heating in the Tropics
  caused by more Sun energy per unit of surface
  area.

24
(No Transcript)
25
2. Tilt of Earths Axis

• Earths axis of spin is tilted 23.5 degrees from
  the plane of Earths orbit around the Sun.
• In WINTER we lean away from the Sun and get only
  INDIRECT (weaker) energy from the Sun.
• In SUMMER we lean towards the Sun, causing the
  Suns energy to strike us more DIRECTLY
  (stronger).

26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Summer Tilted Toward Sun
30
Winter Tilted Away from Sun
31

• Sketch the diagram of the tilt of the axis in
  your class notes.
• Because of the tilt, one hemisphere of the Earth
  will get more intense Sun energy at a given time.
• Result is Northern Hemisphere and Southern
  Hemisphere seasons are opposite.

32
(No Transcript)
33
3. Parallelism - Earths North Pole always
points in the same direction as the Earth orbits
the Sun.

• What star does the Earths North Pole always
  point at?

34
(No Transcript)
35

• The result of parallelism is that each hemisphere
  gets more energy at different times (seasons) as
  the Earth orbits the Sun.
• Parallelism (and the tilt of the Earths axis)
  also defines the latitude of
• Tropic of Cancer (23.5 N)
• Tropic of Capricorn (23.5 S)
• Arctic Circle (66.5 N)
• Antarctic Circle (66.5 S)

36
(No Transcript)
37
(No Transcript)
38
Special Dates of the Seasons - 1

• Summer Solstice - first day of Summer - June
  21-22
• Sun directly over the Tropic of Cancer at noon.
• longest day of the year in the Northern
  Hemisphere.
• Autumnal Equinox - first day of Fall - September
  22-23
• at noon the Sun crosses the Equator into the
  Southern Hemisphere.
• equal day and night.

39
Special Dates of the Seasons - 2

• Winter Solstice - first day of Winter - December
  20-21
• Sun is directly over the Tropic of Capricorn at
  noon.
• shortest day of the year in the Northern
  Hemisphere.
• Vernal Equinox - first day of Spring - March
  20-21
• at noon the Sun crosses the Equator into the
  Northern Hemisphere.
• equal day and night.

40
(No Transcript)
41
Heat in the Atmosphere

• The source of heat in the Earths atmosphere is
  the

42
Heat in the Atmosphere

• Remember the electromagnetic spectrum
• When light wave energy from the Sun comes to
  Earth, the wave energy will be
• Absorbed and re-emitted as heat energy
  (thermosphere, stratosphere, surface of Earth),
  OR
• Pass through atmosphere like light going through
  glass (mesosphere), OR
• Reflected from Earths surface like light off a
  mirror boing!

radio - microwave - infrared - visible
light - ultraviolet - x-rays
43
Earths heat balance

• The energy that enters the atmosphere as light
  needs to be about equal to the energy that leaves
  the atmosphere as heat, or else the Earth will go
  into an ice age or heat up too much.
• Sunlight reflected off the Earths surface is
  called albedo (means white in Latin). Black
  soil or asphalt pavement has low (10) albedo.
  New snow or ice has high (90) albedo. Also,
  cloud tops reflect light back into space, and
  cloud bottoms reflect heat back to Earths
  surface.

44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
Heat transfer in the atmosphere

• Heat in the atmosphere is transferred in three
  ways
• By air in contact with a warm surface, like a hot
  parking lot.
• By vertical air currents, like thunderstorms.
• By horizontal air currents Winds.

48
Temperature measurements

• Daily mean high low/2
• Daily range high low
• Monthly mean sum of daily means / of days in
  the month
• Annual mean sum of monthly means/12
• Annual range high monthly mean low monthly
  mean

49

• Temperature is influenced by
• Latitude
• Altitude
• Proximity to water
• Amount of moisture in the air
• (Record examples of each from class.)

50
The Greenhouse Effect

• The greenhouse effect is caused by a build up of
  gases such as methane, carbon dioxide, and water
  vapor in the atmosphere.
• The radiation from the Sun enters the atmosphere
  and changes to heat and is trapped.
• Not all of the heat can escape back to the
  atmosphere and the Earth warms.
• Greenhouse gasses are transparent to light but
  opaque to heat.

51
(No Transcript)
52
(No Transcript)
53

• We will sketch the Greenhouse Effect on Elmo.
  You should have the sketch and explanation in
  your class notes.