1. The Atmosphere

2. Weather vs. climate
Weather: The state of the atmosphere at a given time (hour to hour or day to day)
Climate: A description of aggregate weather conditions, based on observations that take place in a region over a period of years

3. Basic elements of weather & climate
Air temperature
Humidity
Type and amount of cloudiness
Type and amount of precipitation
Air pressure
The speed and direction of the wind

4. Composition of the Atmosphere
Nitrogen: 78%
Oxygen: 21%
Other gases 1%

5. Carbon dioxide Formula: CO2 Absorbs heat energy radiated by earth
Influences heating of the atmosphere

6. Water vapor Formula: H2O Varies from 0-4% composition
Source of all clouds and precipitation
Absorbs or release heat energy (latent heat)

7. Ozone Formula: O3 Ozone is concentrated in the stratosphere
Ozone absorbs harmful ultraviolet radiation from the sun
Ozone is being slowly depleted from the atmosphere due to use of chlorofluorocarbons (CFC’s)

8. Structure of the Atmosphere
Four layers of the atmosphere
Troposphere
tropopause
Stratosphere
stratopause
Mesophere
mesopause
Thermosphere

10. Structure of the Atmosphere (cont.)
50% of our atmosphere lies below an altitude of 3.5 miles above the Earth’s surface

11. Troposphere The bottom layer of the atmosphere
Virtually all life exists in this layer
This layer is responsible for all our weather
Temperature of troposphere decreases with increasing altitude (3.5oF per 1000 ft.)
Outer boundary is called the tropopause

12. Stratosphere This layer lies beyond the tropopause
Temperature remains constant to height of 13 miles, then the temperature will gradually increase
Ozone is concentrated in this layer
Outer layer is called the stratopause

13. Mesosphere
Temperature decreases gradually with increasing height until one reaches the mesopause
At that point temperature reaches around
-90oC (-130oF)

14. Thermosphere Layer extends beyond the mesopause
Temperature rise rapidly and are very high (>1000oC or 1800oF)

15. Earth-Sun relationships
Virtually all the energy that drives the earth’s weather comes from the sun
Solar energy is not evenly distributed over the earth’s surface. Amount of energy depends on latitude and season
Wind and currents are due to unequal heating of the earth

16. Earth’s motions Two principal motions:
1) rotation: Spinning of the earth about its axis
2) revolution: movement of the earth about the sun.

17. When the Earth orbits the Sun, the Earth tilts 23 1/2 degrees from the perpendicular
This is called the inclination of the axis

18. The greater the angle of the sun, the more concentrated to the Earth’s surface.
The sun’s angle is highest in summer, and lowest in the winter

19. Seasons Seasons are based on two contributing factors:
a) length of daylight
b) angle of the sun

20. During the summer solstice (June 21), the Northern Hemisphere is leaning 23 ½ degrees towards the sun
During the winter solstice (December 21), the Northern Hemisphere is leaning 23 ½ degrees away from the sun

21. During the autumnal and spring equinoxes (September 22 & March 21), the Earth is tilted 0o from the sun.

22. Facts about the summer solstice
Occurs June 21 or 22
Vertical rays of the sun are striking the Tropic of Cancer (23 ½ north latitude)
Northern Hemisphere are experiencing the greatest length of daylight
Locations north of the Tropic of Cancer are experiencing the highest noon Sun angles

23. The farther you are north of the equator, the longer the period of daylight, until the Arctic Circle is reached, where the daylight lasts for 24 hours
The opposite occurs during the winter solstice

24. Heat & Heat transfer
Heat: Form of energy that moves from a warmer body to a cooler body
If two objects of unequal temperature are in contact with each other, heat will travel from the warmer body to the cooler body.
The temperature of the warmer will decrease, temperature of the cooler body will increase

25. Mechanisms of Heat Transfer
Conduction
Convection
radiation

26. Conduction
Transfer of heat through matter by molecular activity (direct contact)
Transfer occurs by collisions from one molecule to another
Conduction of heat varies from one material to another
Metals are the best heat conductors

27. Convection
Transfer of heat by mass movement or circulation within a substance
Convection primarily takes place in fluids
This is the type of heat transfer that primarily occurs in the atmosphere

28. Radiation Transfer of energy through a vacuum or space
Solar energy reaches our planet by way of radiation

29. Forms of Radiation Visible Infrared Ultraviolet X-rays Microwaves
radiowaves

30. Radiation (cont.)
All these radiations constitutes a collection of radiations called an electromagnetic spectrum
Each of these radiations have a characteristic wavelength
Wavelength: Distance from one crest to the next

31. Visible radiation Radiation which can be seen by our eyes.
Visible radiation can be broken down into its seven colors (what are the colors?)

32. Infrared radiation
Radiation is longer in wavelength than visible light
Lies above the red region of the visible spectrum
Responsible for heat radiation

33. Ultraviolet radiation
Shorter wavelength than visible radiation
Lies below the violet region of the visible spectrum
Primary source of radiation from the sun. Responsible for sunburn

34. Basic Laws of Radiation
All objects give off radiation, regardless of temperature
Hotter objects give off more radiation than colder objects
The hotter the radiating body, the shorter the wavelength of maximum energy
Objects that are good absorbers are also good emitters as well

35. Fate of incoming solar radiation
When radiation strikes an object, three possible outcomes can occur:
1) Radiation can be absorbed by the object
2) Radiation can be transmitted (go through) the object
3) Radiation can be reflected (bounced off) an object

37. Solar radiation and our Earth
About 50% of the solar energy reaching the atmosphere is absorbed by the Earth’s surface
About 30% is reflected back into space by the atmosphere, clouds, and other reflective surfaces
About 20% is absorbed by clouds and the atmosphere’s gases

38. Reflection
About 30% of the solar energy reaching the outer atmosphere is reflected back to the space
This fraction of total radiation that is reflected is called albedo

39. Scattering
Occurs when a beam of light produces a larger number of weaker rays
The weaker rays travel in all directions
Scattering of light accounts for the blueness of our sky

40. Absorption Gases are selective absorbers
Nitrogen is a poor absorber of solar radiation
Oxygen removes most of the shorter wavelength ultraviolet radiation and ozone absorbs most of the ultraviolet rays from the stratosphere

41. Factors affecting albedo
Amount of cloud cover
Sun’s angle
Presence of particulate matter
Nature of the Earth’s surface

42. The greenhouse effect
This is the increase in the temperature of a planet’s atmosphere caused when infrared-absorbing gases are introduced into the atmosphere

43. Greenhouse gases Carbon dioxide Water vapor
Without the greenhouse effect, life on our planet will not exist

44. Temperature controls
A factor that causes temperature to vary from place to place and from time to time

45. Why Temperatures Vary
Factors other than latitude that exert a strong influence on temperature include heating of land and water, altitude, geographic position, cloud cover, and ocean currents.

46. Temperature Controls Land and Water
Land heats more rapidly and to higher temperatures than water. Land also cools more rapidly and to lower temperatures than water.

48. Geographic Position
The geographic setting can greatly influence temperatures experienced at a specific location.
Leeward vs. Windward
Rain Shadow

51. Altitude
The altitude can greatly influence temperatures experienced at a specific location.
The higher into the troposphere, the cooler the temperature

53. Cloud Cover and Albedo
Albedo is the fraction of total radiation that is reflected by any surface.
Many clouds have a high albedo and therefore reflect back to space a significant portion of the sunlight that strikes them.

54. Albedo
The fraction of radiation that is reflected by the earth’s surface
Albedo of the Earth, as a whole is 30%
Albedo varies on Earth from place to place and from time to time

55. 50% of the solar energy that strikes the Earth’s surface is absorbed
Most of this radiation is radiated skyward
The radiation that the Earth gives off has longer wavelengths than solar radiation

56. World Distribution of Temperature
Isotherms are lines on a weather map that connect points where the temperature is the same.
Isotherms generally trend east and west and show a decrease in temperatures from the tropics toward the poles.