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The Atmosphere.

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Presentation on theme: "The Atmosphere."— Presentation transcript:

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

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.

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