1. Heating the Atmosphere

2. How do heat and temperature differ?
Heat is the ENERGY transferred from one object to another due to a difference in their temperatures. Heat flows from HIGHER to LOWER temperatures.
TEMPERATURE is a measure of the average kinetic energy of the individual atoms or molecules in a substance.
When air transfers energy to a cooler object, the air’s particles move slower and its temperature drops.

3. Energy Transfer Three mechanisms of heat transfer are: Conduction
Convection (through movement of a fluid like water or air)
Radiation
These mechanisms operate to transfer energy between Earth’s surface (both land and water) and the atmosphere.

4. Conduction
Conduction is heat flow through matter by molecular activity (collisions of one molecule with another). The materials have to be TOUCHING.
Some materials, like metals, are very good conductors, while others, like air, are very poor.
In the atmosphere, conduction is only important between Earth’s surface and the air directly in contact with the surface (touching the ground).
For the atmosphere as a whole, conduction is the LEAST IMPORTANT method of heat transfer.
Much of the HEAT transfer that occurs in the atmosphere is carried on by CONVECTION.

5. Convection
Heat flow through mass movement or circulation of a fluid (like water or air) where the molecules or atoms are free to move about within a substance.
Convection depends on unequal heating. As heat is absorbed by some of the fluid, it expands, becomes less dense, and rises due to buoyancy. Colder, denser fluid sinks, flows in (to replace the heated fluid), and becomes heated in its turn, continuing the circulation pattern.

6. Convection (cont.)
In the atmosphere, most of the heat acquired by the lower atmosphere through radiation and conduction is transferred by convective flow in the air.
Convection is also important in the oceans and within the Earth’s mantle, which is solid but behaves like a liquid over long periods of time.

7. Radiation
The Sun is ultimately the source of the energy that creates our weather.
Light and heat are forms of energy that are only part of a large array of energy called the electromagnetic spectrum.

8. Radiation (cont.)
All radiation, whether short wavelengths like x-rays, gamma rays or UV rays or long wavelengths like radio waves, travels through the vacuum of space at 300,000 kps.
Radiation is emitted from a source (it moves away from it) in all directions and in a mixture of wavelengths (sizes).
Unlike conduction and convection, radiant energy can travel through the vacuum of space (no matter or stuff needed!). Solar energy reaches Earth by radiation.

9. Electromagnetic Spectrum
Radio waves have the LONGEST wavelengths.
Gamma waves have the SHORTEST wavelengths.
Visible light is the only portion of the spectrum you can see. Each color corresponds to a specific RANGE OF WAVELENGTHS.
RADIATION travels out in all directions from its source.
Unlike conduction and convection, which need material to travel through, radiant energy can travel through the vacuum of space.

11. Radiation (cont.) Here are the 4 laws governing radiation:
All objects, of any temperature, emit radiant energy.
Hotter objects radiate more total energy than do cold objects.
The hottest radiating bodies produce the shortest wavelengths of radiation.
Objects that are good absorbers of radiation are good emitters as well.

12. Radiation’s Effect on Objects
When radiation strikes an object, there usually are three different results:
Some energy is absorbed by the object. When radiant energy is absorbed, it is converted to heat and causes a temperature increase.
Substances such as water and air are transparent to certain wavelengths of radiation. Radiation is that is transmitted does not contribute energy to the object.

13. What happens to solar radiation?
Some radiation may bounce off without being absorbed or transmitted. Reflection occurs when radiation bounces off an object.
This is the transmitted radiation—it goes right through the atmosphere, being neither absorbed or reflected.

14. Reflection and Scattering of Light
REFLECTION is light bouncing off an object. The reflected light has the same intensity as the incident (incoming) radiation.
SCATTERING produces a larger number of weaker rays that travel in different directions, although most energy is in the forward direction.

15. Scattering
Dust and gas molecules scatter light, giving us our blue sky and diffuse light on cloudy days.
About 50% of the solar radiation that is absorbed at Earth’s surface arrives as scattered light.

16. Earth’s Energy Budget
51% of incoming solar radiation is absorbed by land and sea
4% is reflected from land/sea interface
19% is absorbed by atmosphere and clouds
20% is reflected from clouds
6% is backscattered to space from the atmosphere

17. Earth’s Energy Budget
The atmosphere also plays a major role in heating Earth’s surface.
Remember that all objects radiate heat according to their temperature. Hot objects radiate energy at shorter wavelengths than do cool objects.
Because Earth has a much lower surface temperature than the sun, the radiation that it emits has longer wavelengths than solar radiation does.

18. Earth Radiates in the Infrared
Earth’s energy budget is balanced: incoming solar radiation is balanced by outgoing terrestrial radiation. This outgoing radiation is longwave INFRARED radiation.

19. Greenhouse Effect
Solar radiation (including light) is absorbed by and warms Earth’s surface
(The reflected sunlight isn’t important here, because it doesn’t warm Earth’s surface!) 1

20. Greenhouse Effect (cont.)
Earth’s surface radiates heat energy toward space but at a cooler temperature (as infrared radiation) 2

21. Greenhouse Effect (cont.)
Certain gases in the atmosphere —especially carbon dioxide (CO2) and water vapor—absorb some of this escaping heat energy 3
This has NOTHING to do with the OZONE LAYER!!

22. Greenhouse Effect (cont.)
These gases, in turn, radiate energy both toward space and back towards Earth
This ‘extra’ heat energy keeps Earth habitable 4

23. The nitrogen and oxygen gas molecules in the atmosphere also play NO role in GE.3 2 4 1
Remember, the reflected sunlight doesn’t play a role in the Greenhouse Effect, so ignore it!

24. Greenhouse Effect
Without the Greenhouse Effect, our oceans would be frozen solid!

25. Is the Greenhouse Effect the same thing as Global Warming?
NO! GE is a natural effect caused by certain gases in our atmosphere—CO2, water vapor, methane, and some others—that keeps our planet warm enough to be habitable (Remember: 59°F instead of 0°F!)
Global warming is the increase of global temperatures as a result of increases in carbon dioxide and other greenhouse gases (such as water vapor and methane) in the atmosphere.

26. Global Warming
During the 20th Century, Earth’s average surface temperature has increased about 0.6°C, and by 2100 climate scientists predict temperatures will increase by 1.4°C to 5.8°C (2.5°F to 10.4 °F)
What is debated is whether the temperature increase is due to human activities or not. We will discuss this topic in more detail later in the year.

27. What are the basic elements of weather?
When someone asks what it is like outside, what do we respond?
When someone from another part of the US or another country asks you what the climate is like in Hobbs, what do you answer?
TEMPERATURE is one of the basic elements of weather and climate. We’re going to focus on this element of weather.

28. Why do temperatures on Earth vary?
When the sun’s rays strike the Earth’s surface from directly overhead, they heat the surface more than sunlight that strikes at an angle.
We have already learned that the angle of sunlight depends on the season, because Earth’s axis is tilted 23.5° from vertical.
Another thing that depends on season is the how long the sun is above the horizon (daylength)

29. Because variations in the angle of the sun’s rays and daylength depend upon WHERE you are on Earth (along a circle of LATITUDE), some latitudes get more direct sunlight and therefore more heat than others.

30. Averaged over a year, the regions near the equator (low latitudes) get much more heat than do polar regions (high latitudes).
These variations are responsible for warmer temperatures in the tropics and colder temperatures at the poles.

31. FACTORS AFFECTING TEMPERATURE
A TEMPERATURE CONTROL is any factor that causes temperatures to vary from place to place and from time to time.
Other factors beside LATITUDE are HEATING of LAND and WATER, ALTITUDE, GEOGRAPHIC POSITION, CLOUD COVER, and OCEAN CURRENTS.
Let’s make a foldable for this:

32. LATITUDE
Once again,
Averaged over a year, the regions near the equator (low latitudes) get much more heat than do polar regions (high latitudes).
These variations are responsible for warmer temperatures in the tropics and colder temperatures at the poles.

33. HEATING OF LAND AND WATER
The heating of Earth’s surface controls the temperature of the air above it.

34. Land heats FASTER and HOTTER during the day and cools FASTER and COLDER during the night than water does so…

35. Effect of a Large Body of Water on Temperatures
. . . Being near a large body of water affects temperatures. The RANGE of yearly temperatures is NOT as GREAT near a large body of water. The more constant temperature of the water causes the air passing over it to have a smaller temperature range throughout a year than air over land does.

36. Vancouver, BC is at about the same latitude as Winnipeg, Manitoba, so they both have the same solar angle and length of daylight. Vancouver, however, is on the windward Pacific coast while Winnipeg is far inland. The influence of the ocean is that Vancouver’s year-round temperatures are more moderate, cooler in summer and warmer in winter, than Winnipeg’s.
“More moderate” also means fewer temperature extremes.
ON THE OCEAN = warmer in winter and cooler in summer overall than inland
INLAND = more extreme temps

37. Mean Monthly Temperatures for Vancouver and Winnipeg

38. Another Land-Water Effect
Another important land and water effect is due to the different amounts of land and water in the Northern and Southern Hemispheres.
The Northern Hemisphere has 61% water and 39% land.
The Southern Hemisphere has 81% water and 19% land.
Which hemisphere would you predict has smaller annual temperature variations (is more moderate)?

39. Altitude
For the same latitude, higher elevations experience lower overall temperatures than do lower elevations.
This means that at HIGHER elevations, winter temperatures are COLDER and summer temperatures are COOLER than at lower elevations.

40. Mean Monthly Tems for Quito and Guayaquil

41. Geographic Position
Coastal locations where the wind blows onto the land (WINDWARD) or away from the land (LEEWARD) have very different weather. A windward coast gets the moderating influence of the water (cool summers and mild winters) while the leeward coast does not (stuck with hot summers and cold winters).
Mountains can act as barriers, cutting an area off from a moderating influence that it would otherwise have.

42. Mean Monthly Temps for Eureka and NYC

43. Mean Monthly Temps for Seattle and Spokane

44. Understanding Check
We have looked at the effects of LATITUDE, LAND and WATER, ALTITUDE, and GEOGRAPHICAL POSITION.
Consider this situation:
Denver is far inland but at a high elevation; San Francisco is on the Pacific Coast. They have similar latitudes.
What would you expect to be the differences in climate between them?
Talk with a partner and answer this on your white board (2 min).

45. Cloud Cover During the Day
Clouds reflect a significant portion of the sunlight that reaches them back towards space because they have a high albedo.

46. A cloudy day will be cooler than if it were a clear day.
Cloud Cover Effects
ALBEDO is the fraction of total radiation that is reflected from a surface. Clouds and snow have a high albedo, asphalt has a low albedo.
The amount of cloud cover strongly affects how much sunlight reaches the Earth’s surface. The more cloudy it is, the less sunlight reaches the surface.
A cloudy day will be cooler than if it were a clear day.

47. Nighttime Clouds
But, clouds at night have the OPPOSITE effect. They act like a BLANKET.
Clouds absorb the outgoing radiation from the Earth, trapping it and reradiating some of it back toward the surface.
Overall, clouds act to keep temperatures cooler during the day and warmer at night, moderating the daily temperature range.

48. Ocean Currents
The Gulf Stream is a warm current that flows from Florida across the Atlantic Ocean to Great Britain and moderates its climate.

49. Computer Model of the Gulf Stream Surface Temperature, 2005,

50. Worldwide Temperature Distribution
ISOTHERMS are lines that connect points with the same temperature.
If you look at world map that shows isotherms, you’ll notice that isotherms generally trend east and west and show a decrease in temperatures from the tropics toward the poles.
NOTE: Isotherms are NOT the same as latitude even if they trend east and west.

51. Global Map Showing Isotherms

52. Did you see that temperatures are warmest near the tropics and coldest near the poles? (We do know that there are differences due to the other factors, though.)
This result shows that the largest influence on temperature is (drumroll, please)
a locations’ latitude.