Section E - Global Energy System

What is electromagnetic energy? (3)

• forms of energy- electric and magnetic waves that propagate in the same direction at 90 degrees to one another

• travel in packets of energy called photons

• aka light radiation electromagnetic waves/ radiation

Electricmagnetic energy can be described by (3)

1. wavelength (nm, um, cm, m, etc.)

1. frequency (htz)

2. energy

Everything above absolute zero (0 degrees K = -273 degrees C) emits _

electricmagnetic energy

At absolute zero, molecular motion _ and no electromagnetic energy is emitted

stops

Wavelength (3)

• wave trough

• wave crests

• amplitude

Energy

hotter objects (sun) emit more energy at shorter wavelengths than cooler objects (earth)

Wein’s Law (2)

• hotter objects emit shorter wavelengths

• inverse relationship between temperature of an object and wavelength that it emits

Sun mostly emits _ energy and earth mostly emits _ energy

• shortwave

• longwave

Stefan-Boltzmann Law (3)

• direct relationship between the absolute temperature and the amount of radiation

• hotter objects emit more radiation than the sun

• earth emits less radiation than the sun

Micrometer (1μm) = _m (1×10^-6)

1/1,000,000

Nanometre (1nm) = _m (1×10^-9)

1/1,000,000,000

What does the electromagnetic spectrum show? (2)

• classification system

• short-wave (solar) radiation

  • short/ near infrared, visible light, uv

Why is infrared radiation (0.7 to 1,000 μm) of interest to geographers? (2)

• earth’s radiation is entirely (thermal) infrared (longwave)

• ~45% of the solar energy infrared (shortwave)

Why is visible light (0.4 to 0.7 μm) of particular interest to geographers?

47% of the solar energy (shortwave)

Why is UV (0.01 to 0.4 μm) of particular interest to geographers? (3)

• ~8% of solar energy

• most filtered by ozone layer

• shortwave

Terrestrial means:

earth

Terrestrial Radiation (2)

• longwave (thermal infrared)

• wavelengths of outgoing radiation from earth

Wavelengths of incoming radian from the sun is:

solar radiation

Greenhouse effect av. temp of earth

~15 degrees C

What is the surface and internal temperature of the sun?

• 6,000 degrees C

• 16 million degrees C

How far is the sun from the earth?

150 million km

What is the speed of light of the sun?

300,000 km/s

How many minutes from the sun to reach the earth?

~8 min

What does nuclear fusion (H → He) from the sun create?

electromagnetic (solar) radiation

Solar Radiation (3)

• travels through space without loss of energy

• intensity diminishes with distance from the sun

• small fraction intercepted by the sun (0.000,000,000,45)

Inverse square law of intensity: I/ d² where? (2)

I: intensity of radiation at 1 unit distance

d: distance travelled in those units

Effect of inverse square law of sun

4.5 billionths of sun’s energy intercepted by earth

What is insolation (4)

• incoming solar radiation

• solar constant/ irradiance

• only small portion reaches the surface as the earth as it moves through atmosphere solar energy is transmitted, reflected, scattered, absorbed (heating)

• 1367 w/m²

As solar radiation flows through earth’s atmosphere, it may flow unimpeded (transmission), or it may be modified by a variety of processes: (3)

• absorption

• reflection

• scattering

The uv region covers the wavelength range 100-400 nm and is divided into three bands:

• UVA (315-400nm)

• UVB (280-315)

• UVC (100-280)

UVA (2)

• most reaches earth

• transmits through window glass

UVB (3)

• ~10% reached earth

• 90% absorbed by ozone, water vapor, oxygen and carbon dioxide

• blocked by window glass

UVC

all absorbed by atmosphere

UV reaching earth is largely _ and small component _

• UVA

• UVB

The flow of solar radiation in the atmosphere is (direct/indirect)

both

Absorption

gases and particulates interrupt the flow of radiation by absorbing specific wavelengths and gain heat

Reflection

redirected radiation returning to space and has no heating effects

Scattering (2)

• solar radiation bounces of an object in a variety of directions and has no heating effect

• amount depends on wavelength size, shape and composition of molecules/ particles

Rayleigh scattering- blue sky (2)

• shorter visible wavelengths (blue and indigo) are scattered more easily than longer wavelengths

• creates blue sky, not indigo because there is more blue light and human eyes sense blue light more readily

Scattering- red sunsets

sun is low in the sky and light passes through so much atmosphere that all the blues are scattered away, leaving longer wavelengths (red, yellow, orange)

The greenhouse effect (2)

• shortwave radiation from the sun is more transmissible through the atmosphere compared to longwave

• shortwave is absorbed at the surface and longwave is emitted by the earth

What is counterradiation?

longwave radiation emitted by the surface, absorbed by greenhouse gases and re-radiated back towards the surface as longwave

Of the 45% of solar radiation that reaches the surface of the earth, 96% of energy is absorbed by:

the land and water bodies and stored as heats

Heat that can be sensed and measured

sensible heat

Heat that is hidden and cannot be measured

Latent heat

Stored energy gets lost in several ways through: (3)

• conduction to gases in the atmosphere

• removed by evaporation and stored as latent heat

• radiation into the atmosphere or lost to space

What is albedo?

proportion of solar radiation reflected upward from a surface

Earth’s average albedo is

29-34%

Albedo depends on (2)

1. surface characteristics (colour, roughness)

2. angle of incidence

High vs Low Albedo (color)

• high:

  • reflects more light

  • in 100%, reflects 80%

• low

  • absorbs more light

  • in 100%, reflects 10%

Albedo variation with water -angle of incidence

• when sun is higher, water absorbs more

  • lower albedo

• when sun is lower, water reflects more

  • higher albedo

Global distribution albedo (2)

• purple/ blue areas have relatively low albedo (concentrated in oceans where radiation is absorbed)

• poles have higher albedo (ice reflects most of the radiation) and there is a low angle of incidence

What is net radiation?

difference between incoming shortwave and outgoing longwave radiation

Variation in earth’s net radiation due to: (3)

• latitude (angle of incidence)

  • low: surplus

  • high: deficit

• seasonality

• length of day

Variation in net radiation due to seasonality (2)

• seasonal variations in solar radiation on earth

• northern hemisphere

  • net radiation decrease in Jan. and increase in July

The global radiation budget (slide 32)

• excess/ deficit

• global transfer of energy

  • 75% atmosphere circulation, 25% oceanic circulation

What measures the amount of sensible heat?

surface and air temperature

Surface temperature

measure of kinetic energy contained in a region very close to earth’s surface

Atmospheric temperature (2)

• measure of kinetic energy in unit of geographical space within the air

• measured at 1.2 m above the ground

Temperature is determined by:

balance of a substance

Average annual temperature (2)

• average temperature calculated over the course of the year (aka mean annual temperature)

• is controlled mainly by elevation and latitude

Annual temperature range

difference between the average max and average min temperature over a year at a location (seasonality)

Large-scale geographic factors that influence air temperature

• latitude

  • high: high amounts of solar energy

  • low: lower angle of incidence results in less solar energy

• seasons and length of day

Latitude influencing air temperature

• differences in the angle of incidence cause energy to be directed in smaller or larger surface areas

• results in distinct temperature differences

Seasons and length of day that influence air temperature

• axial tilt and migration of subsolar point

  • influences net radiation between hemispheres

  • influences day light length and daily radiation patterns

    • day light length consistent at equtor and vary more with increasing latitude

Local factors that influence temperature - Maritime

maritime places are located within or near a very large body of water and are more moderate and humid climate

Local factors that influence air temperature - Contenent

continental places are surrounded by air masses

• more extreme climates (warmer summers and colder winters)

Land heats and cools more rapidly than water due to: (4)

• specific heat

• transmission

• mobility

• evaporative cooling

Specific heat on continent vs maritime

land:

• land heats more quickly

• low specific heat

water:

• water heats more slowly

• high specific heat

Transmission on continent vs maritime

land:

• radiation does not penetrate surface (land is opaque)

• heats surface area

water:

• radiation penetrates to lower depths (water is transparent)

• heats a volume

Mobility on continent vs maritime

land:

• no mixing of heated and cooled land

• heat dispersed by conduction

• land materials are poor conductors

water:

• mixing of heated and cooled water

• heat dispersed by convection

• water disperses heat broadly and to a depth

Evaporative cooling on continent vs maritime

land:

• limited evaporation

maritime

• high evaporation rates

Maritime (Vancouver) vs Continental (Winnipeg) locations

• Vancouver’s annual temperature range is moderated: ~12 degrees C

• Winnipeg’s annual temperature range is more extreme: ~37 degrees C

Altit