Chapter 1 - Introduction to the Atmosphere
Definitions

Atmosphere - shell of gases around the Earth, and gravitationally bound to it.

Meteorology - the scientific study of the atmosphere.

Weather - the state of the atmosphere at a given time and place.

Climate - the sum of the statistical weather information that helps describe the atmosphere in a given place or region. (Climate data cannot be used to predict the weather.)

Latent Heat - heat energy that is transferred to or from a body, thereby changing its state, but not its temperature. (solid to liquid, liquid to gas - ice to water, water to steam). ! very important ! when water in clouds freezes, it liberates the energy that drives weather systems.

The Elements
  1. Temperature of the air
  2. Humidity of the air
  3. Type and amount of cloudiness
  4. Type and amount of precipitation
  5. Pressure exerted by the air
  6. Speed and direction of the wind

SO - does meteorology have anything to do with meteors?

Atmospheric hazards - see Table 1.1
  1. Floods
  2. Lightning
  3. Tornadoes
  4. Hurricanes
  5. Heat waves
  6. Droughts

SO - what was the single most damaging weather event? What about Katrina?

The Nature of Scientific Inquiry
  1. Observations lead to an hypothesis that can be tested.
  2. Successful hypotheses become theories.
  3. To be a scientific theory, the theory must successfully predict something that was not used to develop the theory
  4. Theories cannot be proved - they can only be disproved.
Observing the Atmosphere
  1. Radiosondes - package of instruments fitted with radio transmitters and flown on a balloon. Measurements of temperature, pressure and relative humidity radioed back to the weather station. Flown twice a day.
  2. Weather radar - familiar from TV
  3. Weather satellites provide wide area coverage. Can deduce pressure patterns from the clouds.
Box 1-1 Monitoring Earth from Space

Tropical Rainfall Weather Mission ( TRMM ) from NASA.

Provides rainfall and heat release associated with rainfall for tropical regions.

Much of Earth's rain falls over the tropical oceans (no ground-based observations).

Earth's Four Spheres
  1. Atmosphere - shell of gases around the Earth, and gravitationally bound to it. Allows life, protects us from the Sun, gives us the Weather
  2. Geosphere - solid Earth = core + mantle + crust.
  3. Hydrosphere - our water (oceans, lakes, rivers, glaciers, underground)
  4. Biosphere - all life on the Earth

The Earth's four spheres plus the solid Earth behave as a System

A System is a group of interacting or interdependent parts that form a complex whole. - e.g., a motor vehicle

Have Open and Closed systems

Feedback - Negative feedback systems work to maintain the system as it is.

Positive feedback drives changes in the system.

The Energy required to drive the Earth as a system comes from

  1. The Sun - drives all processes that occur on or above the Earth's surface
  2. From within the Earth - primordial heat and radioactive decay (small %)
Composition of a Dry Atmosphere (ignore water vapor)
  1. Nitrogen - 78%
  2. Oxygen - 21%
  3. Argon - 1% (from radioactive decay)
  4. Carbon dioxide - 0.04% (influences heating of the atmosphere)
Box 1-2 Creation of Earth's Atmosphere
  1. Early Earth was very hot and molten.
  2. As it cooled, gases dissolved in the molten rocks escaped - Outgassing .
  3. Gases were mostly water vapor, carbon dioxide and nitrogen.
  4. Water led to very heavy rains that cooled the Earth down, and absorbed most of the CO 2 . Nitrogen was left.
  5. Once plants began to grow, they emitted oxygen as a by-product of photosynthesis. Allowed plants and then animals to exist.
Variable Components of the Atmosphere
  1. Water Vapor - between 0 and 4% by volume
  2. Aerosols - are solid or liquid particles suspended within the atmosphere. Water condenses on their surfaces, and they absorb/reflect solar radiation.
  3. Ozone - O 3 formed at altitudes of 10 to 50 km (stratosphere)
Ozone
  1. Formation - UV light from the Sun breaks down an oxygen molecule (O 2 ) into O and O. The Os can then combine with O 2 to form O 3 .
  2. Protects us from UV light from the Sun
  3. Depleted by man-made CFCs. At very high altitudes, CFCs are broken down by the UV light from the Sun, liberating chlorine gas, which combines with and destroys the O 3 .
  4. Ozone hole forms over Antarctica - relatively abundant ice particles in stratosphere helps the CFCs to destroy O 3 .
  5. Loss of ozone leads to higher rates of skin cancer, changes the human immune system, causes cataracts. Increased UV levels also affect plants, animals, and the ocean food chain.
  6. See also Box 1-3 Ozone Reactions in the Stratosphere
  7. Ozone is a pollutant at ground level, a good guy in the stratosphere.
Height & Structure of the Atmosphere

How does the atmosphere change as the altitude increases?

  1. Atmospheric pressure = weight of column of atmosphere above per m 2
  2. Average atmospheric pressure at surface of Earth is 1000 millibars
  3. One half of the atmosphere lies below 5.6 km . Pressure drops by half.
  4. Atmosphere thins out with increasing height
  5. The atmosphere has no real edge
Temperature Changes

Atmosphere is divided into four layers, based on temperature

  1. Troposphere . Bottom layer. Where we live. About 12 km thick. Atmospheric components are very well mixed
  2. Temperature decreases with increasing altitude ( environmental lapse rate ). Average is 6.5 O C per km (called the normal lapse rate ). Sun heats the Earth. As altitude increases, get further away from heat source.
  3. Temperature stops decreasing at the Tropopause , which is at altitudes between 9 and 18 km, depending on latitude
  4. Temperature then increases in the Stratosphere , up to the Stratopause at 50 km. Increase arises from heat generated when UV night creates the ozone.
  5. Temperature then decreases in the Mesosphere , up to the Mesopause at 80 km
  6. Temperature then increases in the Thermosphere to very high values (1000 O C). Increase arises when O and N absorb the longer wavelength UV radiation, and give out heat.
  7. Temperature is a measure of the speed of the individual atoms
Vertical Variations in Composition

Based on composition, the atmosphere is divided into two layers:

Homosphere - up to about 80 km, composition is constant because of mixing

Heterosphere - above 80 km. Gases are arranged in shells. N 2 , O, He, H. N 2 is the heaviest, hydrogen the lightest

The Ionosphere
  1. Lies at altitudes between about 80 and 500 km (and higher)
  2. Caused by photoionization of atoms or molecules of the atmosphere by UV and EUV light from the Sun
  3. Photoionization - the energy of the light from the Sun is absorbed by an electron in an atom, allowing it to escape from its atom.
  4. Result of (photo)ionization is a mixture of positively charged ions and negatively charged electrons.
  5. It is the light electrons that are interesting. Ions are relatively heavy.
  6. The ionosphere has a vertical structure because the Sun's radiation is not monochromatic, and different atoms or molecules are ionized. Layers called D, E, F. (E = electrical; others from alphabet)
  7. D region absorbs radio waves, especially at low frequencies. D & E layers disappear at night.
  8. Electrons in ionosphere slow radio waves down, and thus affect the accuracy of locations determined by using the GPS satellites.
  9. Auroras - aurora borealis / australis. Caused by charged particles from the Sun hitting the atoms of the Earth's atmosphere at about 100 km. The atoms are raised to higher energy levels and emit light as they decay back to the lower energy states.