Chapter 11 Lecture Outline. Heating the Atmosphere

Transcription

1 Chapter 11 Lecture Outline Heating the Atmosphere

2 They are still here!

3 Focus on the Atmosphere Weather Occurs over a short period of time Constantly changing Climate Averaged over a long period of time Generalized, composite of weather

4 Climate Data for New York City

5 Focus on the Atmosphere Elements of weather and climate Properties that are measured regularly: Temperature Humidity Cloudiness Precipitation Air pressure Wind speed and direction

6 Composition of the Atmosphere Air is a mixture of discrete gases Major,stable, components of clean, dry air 78% Nitrogen (N 2 ) 21% Oxygen (O 2 ) Argon and other gases 0.036% Carbon dioxide (CO 2 )

7 Composition of the Atmosphere

8 (a) The solid blue line shows the average yearly measurements of CO2 in parts per million (ppm) at Mauna Loa Observatory, Hawaii, from 1958 to The jagged dark line illustrates how higher readings occur in winter where plants die and release CO2 to the atmosphere, and how lower readings occur in summer when more abundant vegetation absorbs CO2 from the atmosphere. (b) The insert shows CO2 values in ppm during the past 1000 years from ice cores in Antarctica (orange line) and from Mauna Loa Observatory (blue line). (Mauna Loa data NOAA-Ice Core data courtesy of Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory

9 Composition of the Atmosphere Variable components of air Water vapor (gas) Up to 4% of air s volume Forms liquid - clouds and precipitation It is also a greenhouse gas Important role in absorbing and releasing latent heat during phase change Aerosols Tiny solid and liquid particles Water vapor can condense on solids Reflect sunlight Color sunrise and sunset

10 The scattering of light by air molecules. Air molecules tend to selectively scatter the shorter (violet, green, and blue) wavelengths of visible white light more effectively than the longer (orange, yellow, and red) wavelengths.

11 Blue skies, red skies, and white clouds Selective scattering of incoming solar radiation causes reflectance in portion of the electromagnetic spectrum that correspond with the colors our eyes detect. At noon, the sun usually appears a bright white. At sunrise and at sunset, sunlight must pass through a thick portion of the atmosphere. Much of the blue light is scattered out of the beam, causing the sun to appear more red.

12 Composition of the Atmosphere Variable components of air Ozone Three atoms of oxygen (O 3 ) Distribution not uniform Concentrated between 10 and 50 km above the surface Absorbs harmful UV radiation Human activity is depleting ozone by adding Chlorofluorocarbons (CFCs)

13 Ozone Depletion

14 Composition of the Atmosphere The darkest color represents the area of lowest ozone concentration, or ozone hole, over the Southern Hemisphere. Notice that the hole is larger than the continent of Antarctica. A Dobson unit (DU) is the physical thickness of the ozone layer if it were brought to the earth s surface, where 500 DU equals 5 millimeters.measured by TOMS.

15 Vertical Structure of the Atmosphere Atmospheric Pressure Variation with Altitude Atmospheric pressure is the weight of the air above. Average sea level pressure is 1000 millibars or 14.7 psi Pressure decreases with altitude Half of atmosphere is below 3.5 mi (5.6 km) 90% of atmosphere is

16 Gasses are compressible density(m/v) greatest at surface

17 Vertical Structure of the Atmosphere Atmospheric layers based on temperature Troposphere Bottom layer Temperature decreases with altitude Environmental lapse rate Average 6.5 C per km or 3.5 F per 1000 feet Thickness varies Average height is about 12 km Outer boundary is the tropopause Where weather happens!

18 Vertical Structure of the Atmosphere The environmental lapse rate is variable It is the actual environmental lapse rate (change in temperature) for any particular time and place Measured with a radiosonde Attached to a balloon and transmits data by radio

19 Vertical Structure of the Atmosphere Stratosphere 12 to 50 km Temperature increases at top Outer boundary is the stratopause Mesosphere 50 to 80 km Temperature decreases Outer boundary is the mesopause Thermosphere No well-defined upper limit Fraction of atmosphere s mass Gases moving at high speeds

20 Earth Sun Relationships Earth motions Rotates on its axis Counterclockwise or Clockwise? Revolves around the Sun Same Question? Seasons - What causes them? Result of: Changing Sun angle Changing length of daylight NOT our distance from Sun

21 The elliptical path (highly exaggerated) of the earth about the sun brings the earth slightly closer to the sun in January than in July.

22 One other Key Factor! The axis of rotation is tilted from a normal to the plane of revolution around the Sun (ecliptic plane)

23 What effect does Sun angle have on the path of rays through the atmosphere?

24 What effect does Sun angle have on the concentration of energy at the surface?

25 Earth Sun Relationships Seasons Caused by Earth s changing orientation to the Sun Axis is inclined 23.5º Axis is always pointed in the same direction What effect does this have on length of daylight?

26 Earth Sun Relationships Special days (Northern Hemisphere) Summer solstice: June Sun s vertical rays located at Tropic of Cancer 23.5º N latitude Winter solstice: December Sun s vertical rays located at Tropic of Capricorn 23.5º S latitude Autumnal equinox: September Sun s vertical rays located at equator (0º latitude) Spring equinox: March Sun s vertical rays located at equator (0º latitude)

27 Earth-Sun Relations

28 June Special days (Northern Hemisphere) Summer solstice Sun's vertical rays are located at the tropic of Cancer (23½ N latitude)

29 Autumnal equinox September Sun's vertical rays are located at the equator (0 latitude)

30 Winter solstice December Sun's vertical rays are located at the tropic of Capricorn (23½ S latitude)

31 Spring equinox March Sun's vertical rays are located at the equator (0 latitude)

32 Differences in latitude effect differences in temperature ranges between summer/winter

33

34 Energy, Heat, and Temperature Heat is synonymous with thermal energy Temperature refers to the intensity, or degree of "hotness" Heat is always transferred from warmer to cooler objects Mechanisms of heat transfer Conduction Molecular activity Convection Mass movement within a substance Radiation (electromagnetic radiation) Gamma waves, X-rays Ultraviolet,visible, infrared Microwaves and radio waves

35 Electromagnetic Spectrum

36 Energy, Heat, and Temperature

37 Energy, Heat, and Temperature Laws of Radiation 1. All objects emit radiant energy 2. Hotter objects radiate more total energy per unit area than colder objects (Stefan-Boltzman Law) 3. Hotter objects radiate more short-wavelength radiation than cooler objects (Wien s Displacement Law) 4. Good absorbers of radiation are good emitters as well (Kirchoff s Law)

38 Stefan-Boltzmann Law Hotter objects radiate more total energy per unit area than do cooler objects

39 The hotter the radiating body, the shorter the wavelength of maximum radiation

40 Kirchoff s Law At equilibrium, the radiation emitted must equal the radiation absorbed. Therefore, 1- e = R where e is the emissivity and R is the reflectivity. The equation holds when the quantities are appropriately averaged over wavelength, but not necessarily at any given wavelength (incident visible light can be reradiated as infrared). Objects that are good absorbers of radiation are good emitters as well!

41 Heating the Atmosphere Incoming solar radiation (INSOLATION) Atmosphere is largely transparent to incoming solar radiation Atmospheric effects Reflection Albedo (percent reflected) Scattering Absorption Most visible radiation reaches the surface About 50% absorbed at Earth s surface

42 Heating the Atmosphere

43 Atmosphere Energy Balance

44 Heating the Atmosphere Difference between reflection and scattering

45 The scattering of light by air molecules. Air molecules tend to selectively scatter the shorter (violet, green, and blue) wavelengths of visible white light more effectively than the longer (orange, yellow, and red) wavelengths.

46 Heating the Atmosphere Albedo, or refectivity of various surfaces.

47 Heating the Atmosphere Radiation from Earth s surface Earth re-radiates energy in longer (IR) wavelengths Terrestrial radiation Terrestrial radiation is absorbed by Carbon dioxide and water vapor Lower atmosphere is heated from Earth s surface Heating of the atmosphere is termed the greenhouse effect

48 Heating the Atmosphere

49 Greenhouse Effect

50

51 What has happened here?

52 Human Impact on Global Climate CO 2 levels are rising Industrialization of the past 200 years Burning fossil fuels coal, natural gas, and petroleum Deforestation Present CO 2 level is 30% higher than its highest level over the past 650,000 years

53 Human Impact on Global Climate

54 US Energy Consumption and CO 2 Produced

55 A. Temp. change in C since 1880 B. Year 2011 difference from mean

56 Human Impact on Global Climate Various scenarios for future - orange if levels of CO2 held constant at 2000 levels.

57

58 For the Record: Air Temperature Data Daily maximum and minimum basis for: Daily mean temperature - avg of highest and lowest T of 24 hr period Daily range - difference between daily max and min T Monthly mean - avg of the daily mean T s for that month Annual mean - sum of 12 monthly means / 12 Annual temperature range - Difference between warmest and coldest monthly means

59 For the Record: Air Temperature Data Isotherms used to examine distribution of air temperatures over large areas Line that connects points of the same temperature iso = equal, therm = temperature Many different iso maps produced Isobars lines of equal pressure Others..

60 For the Record: Air Temperature Data

61 Why Temperatures Vary: The Controls of Temperature Receipt of solar radiation Other important controls Differential heating of land and water Due to differences in specific heat Heat required to raise T of 1 g, 1 C o Land heats more rapidly than water Land gets hotter than water Land cools faster than water Land gets cooler than water Water is a huge heat reservoir!

62 Why Temperatures Vary: The Controls of Temperature Why the difference?

63 Why Temperatures Vary: The Controls of Temperature Other important controls Altitude Same latitude But, 13,461ft. vs 1608 ft.

64 - Geographic position

65 Why Temperatures Vary: The Controls of Temperature - Cloud Cover and Albedo

66 World Distribution of Temperature Temperature maps Temperatures are adjusted to sea level January and July used for analysis Represent temperature extremes

67 World Distribution of Temperature Global temperature patterns Temperature decreases poleward from tropics Isotherms exhibit latitudinal shift with seasons Warmest and coldest over land

68

69 World Distribution of Temperature Global temperature patterns Southern Hemisphere Isotherms are straighter Isotherms are more stable Isotherms show ocean currents Annual temperature range Small near equator Increases with an increase in latitude Greatest over continental locations