ATMOSPHERIC ENERGY and GLOBAL TEMPERATURES. Physical Geography (Geog. 300) Prof. Hugh Howard American River College

Transcription

1 ATMOSPHERIC ENERGY and GLOBAL TEMPERATURES Physical Geography (Geog. 300) Prof. Hugh Howard American River College

2 RADIATION FROM the SUN

3 SOLAR RADIATION Primarily shortwave (UV-SIR) Insolation Incoming Solar Radiation Controlled by circle of illumination, length of day, latitude, etc. Can be transmitted through Atmosphere Water

4 Sun Emits Primarily Shorter Wavelengths

5 SCATTERING and REFRACTION Scattering (Diffuse Radiation) Reflection of radiation in all directions Caused by interference with atmospheric molecules or Earth s surface Refraction Bending of radiation, altering its wavelength Like bending light through a prism

6 Scattering of Sunlight (diffuse radiation)

7 Refraction of Sunlight

8 SOLAR CONSTANT The top of the atmosphere receives 1,400 watts/m 2 of solar radiation Radiation is unevenly distributed Insolation at Ground Level

9 SOLAR CONSTANT What happens to this radiation? Reflection: Albedo Albedo is the proportion of reflected radiation Higher for light objects, lower for darker objects Absorption Assimilation and conversion of radiation Raises the temperature of the absorbing body

10 Reflection and Absorption

11 Reflection: Albedo

12 The ENERGY BALANCE A conceptual model that describes what happens to solar radiation as it enters the Earth system Insolation Incoming solar radiation Net radiation Insolation minus outgoing radiation

13 The Energy Balance

14 REFLECTED RADIATION Reflected by clouds: 21% Scattered by atmosphere: 7% Reflected by ground: 3% Total Albedo: 31% This shortwave radiation leaves Earth, and is not converted to longwave (heat) radiation

15 ABSORBED RADIATION Absorbed by ground: 45% 25% direct, 20% diffuse Absorbed by gases and dust: 18% Absorbed by clouds: 3% Absorbed by stratospheric ozone: 3% Total Absorbed Radiation: 69% This shortwave radiation is converted to longwave (heat), and leaves Earth

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17 HEAT and TEMPERATURE

18 Transfer of energy HEAT From warmer objects to cooler objects Different types Sensible Heat Heat that we can sense Measured with a thermometer Latent Heat Heat exchanged with a phase change of water

19 Radiation HEAT TRANSMISSION EMR given off by hot objects Convection Vertical transfer of heat through the movement of air or water; mixing Conduction Transfer of heat from molecule to molecule; contact

20 Transmission of Heat

21 TEMPERATURE A measure of the kinetic energy of molecules (average) How fast they vibrate Measure of sensible heat

22 TEMPERATURE SCALES Fahrenheit U.S. is the only major country to use it Water freezes at 32 and boils at 212 (at sea level; lower w/ increased elevation) Celsius Metric Water freezes at 0 and boils at 100

23 Kelvin TEMPERATURE SCALES International System of Units (SI) The absolute scale Water freezes at 273 and boils at 373 Absolute zero (0 K) Temperature at which all molecular movement stops (no sensible heat)

24 Temperature Scales

25 FACTORS that CONROL AIR TEMPERATURE

26 SEASON and TIME of DAY Season Surplus of insolation during summer Deficit during winter Time of day Surplus of insolation during the day Deficit at night

27 LATITUDE Equatorial regions receive the most insolation, year round Polar regions receive large amounts but only during summer Surplus Between 40 N&S Deficit Above 40 N&S

28 Insolation and Latitude

29 Temperature and Latitude

30 ELEVATION Higher elevations are generally cooler The Environmental Lapse Rate (ELR) Describes how temperatures change in relation to altitude in stationary air The average ELR in the troposphere 3.5 F/1,000 ft (6.4 C/1,000m) (the Normal Lapse Rate)

31 CLOUD COVER Approximately 50-75% of Earth is covered with clouds at any given time Can lower temperatures by reflecting incoming shortwave radiation Can raise temperatures by trapping longwave radiation from Earth (greenhouse effect)

32 LAND-WATER CONTRASTS Maritime Effect Land near large bodies of water lack extremes temperature cycles; temperatures are more consistent Continental Effect Land isolated from large bodies of water has extreme hot and cold temperature cycles

33 Land-Water Temperature Contrasts

34 Continental and Maritime Effects

35 GROUND COVER Wetter ground = cooler Evaporation removes latent heat Lighter ground = cooler Light surfaces absorb less radiation Urban hotter than rural Urban Heat Island Heat generation, limited vegetation, etc. Urban Dust Dome

36 The Urban Heat Island

37 ADVECTION The horizontal transfer of heat through the movement of air or water Areas can be warmed or cooled as advectional winds come and go

38 DAILY and ANNUAL TEMPERATURE CYCLES

39 DAILY TEMPERATURE CYCLE Pattern of temperature change during a 24 hour period The Diurnal Cycle Maximum temperatures Usually occur in mid-afternoon Surface takes time to respond to maximum insolation (at solar noon)

40 DAILY TEMPERATURE CYCLE Temperatures drop after mid-afternoon Less insolation Natural air conditioning High ground temperatures cause warm air to rise; the warm air is replaced by cooler, descending air Minimum temperatures Occur shortly after sunrise

41 Daily Temperature Cycle

42 ANNUAL TEMPERATURE CYCLE Pattern of temperature change during a year Maximum temperatures Usually occur about a month after maximum insolation (summer solstice) Minimum temperatures Usually occur shortly after minimum insolation (winter solstice)

43 ANNUAL TEMPERATURE CYCLE Seasonal temperature extremes are greater toward the poles Poles influenced more by Earth s tilted axis Poles tilt away from the sun dramatically during winter, and toward during summer Six months of light and six of dark at the poles Equatorial temperatures are fairly constant

44 Annual Temperature Cycles

45 LAPSE RATES and TEMPERATURE INVERSIONS

46 LAPSE RATES The Environmental Lapse Rate (ELR) Describes how temperatures change in relation to altitude in stationary air The average ELR in the troposphere 3.5 F/1,000 ft (6.4 C/1,000m) Adiabatic Lapse Rate Will be covered later

47 Environmental Lapse Rate (ELR)

48 TEMPERATURE INVERSION An inverted, or backward lapse rate Temperatures increase with increasing altitude

49 TEMPERATURE INVERSION In the troposphere, inversions can result from the following Cooling of Earth s surface at night, creating a layer of cool air that rests below relatively warmer air Cold air rushing down into valleys from upslope

50 FOG Inversions can cause low-lying fog Air that comes into contact with cold ground can be cooled to the point of condensation Radiation Fog, or Tule Fog Common in the Central Valley

51 Smoke + Fog SMOG Under inversion conditions, pollutants get trapped in the low-lying layer of cool air

52 The GREENHOUSE EFFECT

53 GREENHOUSE EFFECT Natural process that raises average temperatures on Earth by 63 F Makes possible life as we know it Works on the same principles that Make greenhouses warm enough to grow certain plants Make the interior of a car far hotter than the outside temperature on a sunny day

54 GREENHOUSE EFFECT As Earth absorbs shortwave radiation from the sun, Earth gets heated This heat gets radiated from Earth in the form of longwave radiation (heat) Greenhouse gases in the atmosphere absorb the longwave radiation and send it back to Earth Counter Radiation

55 The Greenhouse Effect Counter Radiation

56 ENHANCED GREENHOUSE EFFECT Is not natural Caused by the addition of large volumes of CO 2 and other greenhouse gases to the atmosphere Burning of fossil fuels, removal of forests Causing Climate Change Increased temperatures, flooding (melting of icecaps), and extreme weather

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58 CLIMATE CHANGE CONSENSUS 97% of climate scientists agree that Climate change happening Is very likely the result of human activities Increased addition of greenhouse gases to the atmosphere Most leading scientific organizations have issued statements supporting this position

59 Climate Change Consensus

60 Climate Change Consensus

61 Climate Change Consensus

62 Climate Change Consensus

63 Climate Change Consensus

64 WORLD PATTERNS of AIR TEMPERATURE

65 TEMPERATURE MAPS Represent temperatures and temperature differences Symbolized with Isotherms Lines of constant temperature Any point along a given isotherm represents the same temperature Data derived from weather stations and by interpolation

66 TEMPERATURE MAPS Temperature Gradients Differences in temperatures from one place to the next Identified by spacing of isotherms Isotherms closer together Means a dramatic change Isotherms further apart Means a gradual change

67 Temperature Map: Isotherms

68 AVERAGE TEMPERATURES Warmer toward the equator, colder toward the poles Insolation decreases with distance from equator Coldest/warmest on land, not water Continental Effect Maritime Effect

69 Average January Temperatures

70 AVERAGE TEMPERATURES Equatorial temperatures are more constant than in higher latitudes Insolation is more consistent Higher elevations are colder than lower elevations Andes, Himalayas, etc. Environmental Lapse Rate

71 Annual Average Temperature July Temperatures Cycles

72 Average January Temperatures

73 Average July Temperatures

74 TEMPERATURE RANGES Differences between average January and July temperatures Greatest in northern continental interiors Increased seasonality of polar regions The Continental Effect Southern hemisphere is more stable The Maritime Effect

75 Annual Temperature Ranges

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78 ATMOSPHERIC ENERGY and GLOBAL TEMPERATURES Physical Geography (Geog. 300) Prof. Hugh Howard American River College