Chapter 2 - Heating Earth's Surface and Atmosphere

Question 1

What causes weather?

Answer 1

The unequal heating of Earth’s land-sea surface creates winds and drives the ocean currents, which in turn transport heat from the tropics toward the poles in an unending attempt to balance energy inequalities. The consequences of these processes are the phenomena we call weather.

Question 2

Rotation

Answer 2

The spinning of Earth on its axis that produces the daily cycle of day and night.

Question 3

Revolution

Answer 3

Earth’s movement in a slightly elliptical orbit around the Sun.

Distance between Earth and Sun averages ~150 million km. Because Earth’s orbit is not perfectly circular the distance varies during the course of a year.

Question 4

Perihelion

Answer 4

About January 3, art is ~147.3 million km from the Sun.

When the Earth is closest to the Sun.

Question 5

Aphelion

Answer 5

July 4 - Earth is ~152.1 million km from the Sun.

When the Earth is furthest from the Sun.

Question 6

What causes the seasons?

Answer 6

1. The gradual but significant change in day length.

2. The gradual change in the angle of the Sun above the horizon.

Question 7

How does the seasonal variation in the angle of the Sun above the horizon affect the amount of energy received at Earth’s surface?

Answer 7

1. When the Sun is directly overhead (at a 90* angle), the solar rays are most concentrated and thus most intense. At lower angles, the rays become more spread out and less intense.
2. The angle of the Sun determines the path solar rays take as they pass through the atmosphere. When the Sun is directly overhead, the rays strike the atmosphere at a 90* angle and travel the shortest possible route to the surface. However, rays entering the atmosphere at a 30* angle must travel twice the distance before reaching the surface. The longer the path, the greater the chance that sunlight will be dispersed by the atmosphere, which reduces the intensity at the surface.

Question 8

What causes fluctuations in Sun angle and length of daylight during the course of a year?

Answer 8

The orientation of Earth’s axis to the Sun’s rays is constantly changing.

Question 9

Plane of the Ecliptic

Answer 9

The plane of the Earth’s orbit around the Sun.

Question 10

Inclination of the Axis

Answer 10

The tilt of the Earth’s axis 23 1/2* away from the plane of its orbit (away from perpendicular).

Question 11

Tropic of Cancer

Answer 11

23 1/2* North latitude (23 1/2* North of the equator)

Question 12

Summer Solstice (in Northern Hemisphere)

Answer 12

June 21 or 22

The vertical rays of the Sun strike at the Tropic of Cancer (23 1/2* North of the equator).

First “official” day of summer.

Winter solstice in the Southern Hemisphere.

Question 13

Winter Solstice (in Northern Hemisphere)

Answer 13

December 21 or 22

The vertical rays of the Sun strike at the Tropic of Capricorn (23 1/2* South of the equator).

First “official” day of winter.

Summer solstice in Southern Hemisphere.

Question 14

Tropic of Capricorn

Answer 14

23 1/2* South latitude (23 1/2* South of the equator)

Question 15

Autumnal (Fall) Equinox (Northern Hemisphere)

Answer 15

September 22 or 23

Vertical rays of the Sun strike the equator (0* latitude) because Earth’s position is such that its axis is tilted neither toward nor away from the Sun.

Daylight is 12 hours everywhere on Earth because the circle of illumination passes directly through the poles thus dividing the lines of latitude in half.

Spring equinox in Southern Hemisphere.

Question 16

Spring Equinox aka Vernal Equinox (Northern Hemisphere)

Answer 16

March 21 or 22

Vertical rays of the Sun strike the equator (0* latitude) because Earth’s position is such that its axis is tilted neither toward nor away from the Sun.

Daylight is 12 hours everywhere on Earth because the circle of illumination passes directly through the poles thus dividing the lines of latitude in half.

Autumnal Equinox in the Southern Hemisphere.

Question 17

Circle of Illumination

Answer 17

The boundary separating the dark had of Earth from the lighted half.

Determines the length of daylight versus darkness.

Question 18

Land of the Midnight Sun

Answer 18

Any location where the latitude is greater than 66 1/2* as it will experience 24 hours of continuous daylight (or darkness) at least one day each year.

Question 19

Energy

Answer 19

The capacity to do work. Work is done whenever matter moves.

Question 20

Kinetic Energy

Answer 20

Energy associated with an object in motion.

EX: A hammer driving a nail. Because of its motion, the hammer is able to move another object (do work).

EX: When a solid, liquid, or gas is heated, its atoms or molecules move faster and possess more kinetic energy.

Question 21

Potential Energy

Answer 21

Energy associated with a stationary object that has the capability to do work. EX: Wood, gasoline.

Question 22

Temperature

Answer 22

A measure of the average kinetic energy of the atoms or molecules in a substance.

When a substance gains energy, its particles move faster and its temperature rises and vice versa.

Question 23

Heat

Answer 23

Energy transferred into or out of an object because of temperature differences between that object and its surroundings.

Heat flows from a region of higher temperature to one of lower temperature. Once the temperatures become equal, heat flow stops.

Question 24

Sensible Heat

Answer 24

Heat we can feel and measure with a thermometer.

Question 25

Latent Heat

Answer 25

The energy involved when water changes from one state of matter to another.

During evaporation heat is required to break the hydrogen bonds between water molecules that occurs when water vapour escapes a water body. Because the most energetic water molecules escape, the average kinetic energy (temperature) of the water body drops. Therefore, evaporation is a cooling process. The energy absorbed by the escaping water vapour molecules is termed latent heat (meaning “hidden”) because it does not result in a temperature increase. The latent heat stored in water vapour is eventually released in the atmosphere during condensation.

Question 26

What are the three ways by which the flow of energy can occur?

Answer 26

1. Conduction
2. Convection
3. Radiation

Question 27

Conduction

Answer 27

The transfer of heat through electron and molecular collisions from one molecule to another.

Air is a poor conductor of heat. Consequently, conduction is important only between Earth’s surface and the air immediately in contact with the surface. As a means of heat transfer for the atmosphere as a whole, conduction is the least significant and can be disregarded when considering most meteorological phenomena.

Question 28

Conductors

Answer 28

Objects that are good conductors.

Question 29

Insulators

Answer 29

Objects that are poor conductors.

Contain many small air spaces.

Question 30

Convection

Answer 30

Heat transfer that involves the actual movement or circulation of a substance.

Takes place in fluids.

EX: On a hot, sunny day the air above a slowed field will be heated more than the air above the surrounding woodlands. As warm, less dense air above the flowed field buoys upward, it is replaced by the cooler air above the woodlands. In this way a convective circulation is established.

EX: Heating of Earth’s surface produces thermals of rising air that transport heat and moisture aloft. The rising air cools, and if it reaches the condensation level, clouds form. Rising warmer air and descending cooler air are an example of convective circulation.

Question 31

Thermals

Answer 31

Warm parcels of rising air.

Question 32

Advection

Answer 32

Denotes the primarily horizontal component of convective flow.

Aka wind.

Question 33

Speed of Light

Answer 33

300,000 km/s

Question 34

Wavelength

Answer 34

The distance from one crest of a wave to the next.

Question 35

Visible Radiation

Answer 35

Can be seen.

Shortwave.

Question 36

Infrared Radiation

Answer 36

Cannot be seen by the human eye but is detected as heat.

Shortwave and longwave.

Question 37

Ultraviolet Radiation

Answer 37

Consists of wavelengths that may cause sunburned skin.

Shortwave.

Question 38

What are the laws of radiation?

Answer 38

1. All objects continually emit radiant energy over a range of wavelengths. The temperature of the object must be above absolute zero (-273*C).
2. Hotter objects radiate more total energy per unit area than do colder objects.
3. Hotter objects radiate more energy in the form of short-wavelength radiation than do cooler objects.
4. Objects that are good absorbers of radiation are also good emitters.

Question 39

Shortwave Radiation

Answer 39

High-energy radiation.

Emitted by hot objects.

Question 40

Longwave Radiation

Answer 40

Low-energy radiation.

Emitted by objects at everyday temperatures.

Question 41

Stefan-Boltzmann Law

Answer 41

Mathematically expresses the rate of radiation emitted per unit area. E = (5.67 X 10^-8 W/m^2k^4)(T^4)

Question 42

Wien’s Displacement Law

Answer 42

The relationship between the temperature (T) of a radiating body and its wavelength of maximum emission = C/T

C = Wien’s constant = 2898 umK

Question 43

In what part of the electromagnetic spectrum does the Sun radiate maximum energy? How does this compare to Earth?

Answer 43

Over 95% of all Solar radiation is emitted in wavelengths between 0.1 and 2.5 um, with much of this energy concentrated in the visible and near-infrared parts of the electromagnetic spectrum. Most of its energy is radiated at wavelengths shorter than 4um. Where as Earth’s are longer than 4um.

Question 44

Reflection

Answer 44

The process whereby light bounces back from an object at the same angle and intensity.

Question 45

Scattering

Answer 45

Light bounces back from an object producing a larger number of weaker rays, travelling in different directions. Scattering disperses light both forward and backward (backscattering).

Question 46

What is the fate of incoming solar radiation averaged for the entire globe?

Answer 46

50% of direct and diffused radiation absorbed by land and sea.
30% lost to space by reflection and scattering.
20% of radiation absorbed by atmosphere and clouds.
20% reflected from clouds.
5% reflected from land-sea surface.
5% backscattered to space by the atmosphere.

Question 47

Albedo

Answer 47

The fraction of radiation that is reflected by an object.

Earth’s albedo is 30%

Question 48

Diffused Light

Answer 48

Light produced when small dust particles and gas molecules in the atmosphere scatter solar radiation in different directions.

Question 49

What is the color of the sky based on?

Answer 49

The color of the sky gives an indication of the number of large or small particles present. Numerous small particles produce red sunsets. Whereas large particles produce white (gray) skies. Thus, the bluer the sky, the less polluted, or dryer, the air.

short wavelengths (blue and violet) of visible light are scattered more effectively than are longer wavelengths (red and orange). Therefore, when the Sun is overhead, an observer can look in any direction and see predominantly blue light that was selectively scattered by the gases in the atmosphere. By contrast, at sunset, the oath that light must take through the atmosphere is much longer. Consequently, most of the blue light is scattered before it reaches an observer. Thus, the Sun appears reddish in color.

Question 50

Crepuscular Rays

Answer 50

Rays of light produced when haze scatters light.

Most commonly seen where the Sun shines through a break in the clouds.

Question 51

Atmospheric Window

Answer 51

Longwave infrared radiation in the zone between 8 and 12 micrometers that can escape the atmosphere most readily.

Question 52

Explain why the atmosphere is heated chiefly by radiation from Earth’s surface rather than by direct solar radiation.

Answer 52

None of the atmospheric gases are effective absorbers of radiation with wavelengths between 0.3 and 0.7 um. This region of the spectrum corresponds to the visible light band, which constitutes about 45% of the energy radiated by the Sun. Because the atmosphere is a poor absorber of visible radiation, most of this energy is transmitted to Earth’s surface. Thus, the atmosphere is nearly transparent to incoming solar radiation and direct solar energy is not an effective “heater” of Earth’s atmosphere.

The atmosphere is an efficient absorber of long wave (infrared) radiation emitted by Earth. Water vapour and carbon dioxide are the principal absorbing gases, with water vapour absorbing ~60% of the radiation emitted by Earth’s surface, making it, more than any other gas, account for the warm temperatures of the lower troposphere, where it is most highly concentrated.

Because the atmosphere is largely transparent to solar (shortwave) radiation but more absorptive of the longwave radiation emitted by Earth, the atmosphere is heated from the ground up. This explains the environment (and normal) lapse rate.

Question 53

How is the atmospheric window “closed”?

Answer 53

Clouds that are composed of tiny liquid droplets (not water vapour) are excellent absorbers if the energy in the atmospheric window. Clouds absorb outgoing radiation and radiate much of this energy back to Earth’s surface effectively blocking the atmospheric window and lowering the rate at which Earth’s surface cools.

Question 54

Greenhouse Effect

Answer 54

The heating of the Earth via the atmosphere “trapping” some of its outgoing radiation; the longwave radiation emitted by Earth is absorbed by water vapour, carbon dioxide, and other trace gases in the atmosphere and some is reflected back to Earth.

Question 55

Heat Budget

Answer 55

The annual balance of incoming and outgoing radiation on Earth.

Question 56

What are the components of Earth’s heat budget?

Answer 56

1. Incoming solar radiation (+100).
2. Solar radiation absorbed by Earth’s surface (+50).
3. Lost from Earth’s surface by conduction and convection (-7).
4. Lost by evaporation (-23).
5. Lost by long wave radiation (-20).
6. Absorbed by atmosphere and clouds (+20).
7. Absorbed by atmosphere (+7).
8. Released to the atmosphere by condensation (latent heat) (+23).
9. Longwave radiation absorbed by atmosphere (+8).
10. Solar radiation reflected back and scattered to space (-30).
11. Emitted to space by atmosphere (-58).
12. Longwave radiation to which the atmosphere is transparent (-12).

Question 57

The equator receives more solar radiation than it loses and the higher latitudes lose more radiation than they gain. Why then don’t they keep getting hotter/colder?

Answer 57

The global wind systems and, to a lesser extent, the oceans act as giant thermal engines, transferring surplus heat from the tropics poleward. In effect, the energy imbalance drives the winds and the ocean currents.