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GEOG272 > Sun & insolation > Flashcards

Sun & insolation Flashcards

1
Q

some distances in the Sun-Earth relationship

A
  1. Earth’s avg. distance from sun
    approx. 150 million km, with light
    reaching earth in an avg. of 8
    minutes, 20 seconds
    • Moon avg distance of 384,000 km
      from Earth (1.28 seconds in light
      speed)
  3. Speed of light approx. 300,000
    km/second (186,000 miles/sec), or
    about 9.5 trillion km/year
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2
Q

Definition of Heliophysics

A

– the study of the sun
and its interactions with Earth and
the solar system

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3
Q

main caracteristics of the sun

A
  • Captured about 99.9% of matter from
    original solar nebula; remaining 0.1%
    formed planets, their satellites, asteroids,
    comets and cosmic debris
  • high pressure and temperature in its core
  • nuclei of H atoms are forced together = fused together which forms helium and releases energy (disappearing solar mass -> energy)
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4
Q

definition of radiation

A

energy from a source in the
form of waves or particles =
electromagnetic waves

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5
Q

solar winds definition

A

electrically charged
particles surging outward from
Sun, needing about 3 days to reach
Earth
- Solar winds sometimes augmented
by ‘coronal mass ejections (which are giant explosions on the sun)

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6
Q

radiant energy definition

A

spanning portions of the electromagnetic spectrum

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7
Q

sunspots definition

A

surface disturbances
caused by magnetic storms (can be
12x the size of the Earth!)

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8
Q

characteristics of auroras

A

Latin: ‘dawn; goddess of the dawn’
* Solar winds make contact with Earth’s
magnetic field = magnetosphere (dynamo-like
motions within our planet)
* Coronal mass ejections can cause ‘auroras” in
upper (80-500 km) atmosphere
* borealis in the north, australis in the south

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9
Q

Insolation definition

A
  • INcoming SOLar radiATION
    Varies with:
  • Angle of incident
    radiation
  • Photoperiod
    Diurnal and annual cycles
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10
Q

solar constant definition

A

a.k.a. total solar
irradiance = amount of solar
radiation received by Earth at
altitude of 480 km, within the
Earth’s thermopause (outer
boundary of Earth’s energy
system)
Earth’s energy budget

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11
Q

What are the outputs and inputs of the Earth and what is another word for it ?

A

-shortwave radiation from the sun are transmitted to the surface of the |Earth’s atmosphere and absorbed.
- longer waves from the sun are scattered from the surface of the Earth’s atmosphere (the longer they travel through the atmosphere, becoming more scattered and diffuse)
- the Earth emits longwave radiation into outer space

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12
Q

What are the types of rays the sun emits?

A
  • UV rays
  • rays of visible light
  • shortwave infrared rays
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13
Q

What is the name of the radiation the Earth emits into outer space?

A

the earth emits thermal infrared (there is interception with the long waves emitted by the sun)

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14
Q

What is called an idealized surface and its temperature?

A
  • a “blackbody
    radiator” (an almost perfect
    absorber/radiator of radiant
    energy
  • its temperature is of 6000 K
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15
Q

Which astral body is considered a “blackbody”?

A

the sun , its temperature is of 6000 K

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16
Q

What is the average temperature of the Earth?

A

23˚C, (300˚ K)

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17
Q

What happens if the sun’s temperature increases (even of a little bit)?

A

It results in a
large increase in the rate at
which radiation is emitted

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18
Q

Describe Wein’s Displacement Law (name various characteristics)

A

-Objects radiate energy in wavelengths related to their individual surface temperatures
- Hotter objects (more intense) emit most of their radiation at shorter wavelengths – thus appear bluer
- Cooler objects (less intense) emit most of their radiation at longer wavelengths – thus appear redder
- Blue light has more energy than red light.
- λm = c/T
λm = Wavelength of maximum radiation (in microns)
c = ~2.9 x 10-3m K (a constant)
T = Temperature in Kelvin

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19
Q

What does the absolute zero represent? And how much is it in degrees Celsius?

A

An Absolute zero is the temperature at which particles constitute a minimal amount of heat. An absolute zero is also called the zero kelvin because it is zero on the Kelvin scale.
0 K = -273 degrees Celsius

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20
Q

Stefan-Boltzmann Law

A

the law speculates that when the temperature increases, the emissive power increases too.
It’s described with the following formula:
E = Ɛ T^4 which means: The total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature”.
(E (aka “P”, “M”, etc.) is emissive power (“FLUX”) of surface in Watts per m2
 is the Stefan-Boltzmann constant (5.67 x 10^8 Wm^-2 K^-4
Ɛ = emissivity of surface (estimated)
(Note: in some formulas, the estimated
emissivity of a surface is not included, thus is
assumed to be 1.0, or a perfect black body)

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21
Q

What is the definition of a perfect black body?

A

A black body is an object that can absorb perfectly entire electromagnetic spectrum and at thermal equilibrium it emits all electromagnetic radiation called as black body radiation.

22
Q

How is the emissive power of surface also called?

A

“Blackbody radiation”

23
Q

waves definition

A

a disturbance or variation that
transfers energy progressively from point to point in a medium

24
Q

what are photons?

A

Photons are the particle form of light.

25
Q

electromagnetic waves

A

EM waves are created as a result of vibrations between an electric field and a magnetic field (oscillating magnetic and electric fields).

26
Q

frequency definition

A

The frequency of the pulsations (the number of
waves that occur per time unit – usually per second) determines the characteristics of the transmitted energy. For example, high-frequency sound waves are high-pitched, and high-frequency light waves are energetic in the ultraviolet part of the spectrum

27
Q

the sun electromagnetic spectrum composition

A

-Typical visible light wave frequencies range from 400-484 THz (red) to 380-450 THz (violet), with wavelengths ranging from red (750 nm, or 0.75 microns) to violet (380 nm or 0.38 microns) view image on word

-8% ultraviolet light (UV), X-ray,
and gamma-ray wavelengths
* 47% visible light wavelengths
* 45% infrared wavelengths

28
Q

Long-wave radiation: From Earth to space?

A

-At the Earth’s avg. temperature radiation
ranges from about 3 to 30 micrometers, and
peaks at about 10 micrometers in the thermal
infrared region
-Much of earth’s surface radiation is absorbed
by the atmosphere (esp. at 6-8, 14-17, and above 21 micrometers).

29
Q

Who are the primary absorbers of the terrestrial long-wave energy?

A

Water and CO2 (which explains global warming)

30
Q

Short-wave radiation: from sun to the Earth?

A

-Solar energy received at the surface ranges from about 0.3 to 3 micrometers
-Sun’s output peaks in the visible part of the spectrum
-Solar energy passes through the atmosphere, subject to absorption and scattering

31
Q

What is the transmissivity: atmospheric ‘windows?

A

The ability of the atmosphere to allow radiation to pass through.
* varies with wavelength and type of
radiation.
* Some wavelengths act as
“windows” and allow radiation to
more easily pass through, useful in
remote sensing / satellite imagery.

32
Q

Why are daily net radiation negative in higher altitudes ?

A

Because the Earth’s climate system loses
more energy to space than it gains from the Sun.

33
Q

What is the emissivity (compared to the transmissivity)

A

It”s another characteristic of the earth’s atmosphere. For example, in the diagram of atmospheric windows we can see that the bands of water vapor and carbon dioxide that absorb some of the EM spectrum, while other
bands allow it through (the gaps, or
windows). (View image in word doc)

34
Q

What does the daily radiation patterns at the top of the atmosphere represent?

A

-Balance between incoming short-wave energy from the Sun and all outgoing radiation
from Earth and the atmosphere (energy
inputs – energy outputs)
-

35
Q

which gases absorb almost all UV radiation at wavelength shorter than about 0.3 micrometers?

A

Oxygen and ozone (O3)

36
Q

What are isolines?

A

connect points of equal value

37
Q

Sun Angle and Insolation Intensity

A

When the angle of the sun’s rays is more inclined (45 degrees) vs perpendicular (90 degrees) it covers more surface of insolation on the Earth. (View image on word doc)

38
Q

What is the inverse Square Law applied to light?

A

-It describes the amount of radiation received.
-Energy at twice the distance from the
source is spread out over four times
the area = ¼ the energy
* So, the intensity (I) of the sunlight
(radiation) is more spread out
(weaker) as it is dispersed over a
distance (through space).
-Total energy is constant so
if distance increases, the intensity decreases per unit area.

39
Q

Define photoperiod:

A

Recurring cycle of daily light & dark periods.
When the photoperiod increases, the total insolation increases also over a 24-hour period

40
Q

How can insolation be lost (from the sun to the Earth) ?

A

from various mechanism:
1. absorption
2. scattering
3. reflection

41
Q

Describe albedo:

A

-It’s the reflective quality of a surface. It’s expressed as percentage
of reflected insolation to incoming insolation.
-All light reflected = 100%= good albedo
-All light absorbed = 0% = bad albedo
-Earth average albedo = 30 %

42
Q

How does the angle of incidence of radiation influence albedo?

A

When the angle of incidence of radiation decreases, the albedo increases.

43
Q

How does the color of the surface affect the albedo?

A

the lighter the color is the higher is the albedo of the surface.

44
Q

How does the surface texture affect the albedo?

A

The smoother the surface is the higher is the albedo.

45
Q

What are three things that affect the albedo?

A
  1. The angle of incidence of the radiation
  2. The color of the surface
  3. the texture of the surface
46
Q

What does the net radiation formula equal to?

A

(Incoming insolation shortwaves - reflected insolation) + (incoming longwave radiation - outgoing longwave radiation)

47
Q

Why is the sky blue?

A

Blue light in insolation is scattered by gas molecules more intensely than the other colors, so it’s the one we see the most of within the visible spectrum.

48
Q

What is rayleigh scattering?

A

It’s the dispersion of electromagnetic radiation by particles that have a radius less than approximately 1/10 the wavelength of the radiation.
blue light, at the short wavelength end of the visible spectrum, will be scattered much more strongly than will the long wavelength red light (which we see more at sunsets due to the different angle of incidence).

49
Q

Why are clouds white?

A

-Because of phenomenon called Mie scattering (non-molecular scattering, or aerosol particle scattering)
-It takes places in the lower 4,500 meters of the atmosphere, where there may be many
essentially spherical particles present with diameters approximately equal to the
size of the wavelength of the incident ray.
-These particles can include smoke,
water droplets (e.g., in clouds), dust,
pollen and other particles

50
Q

What is Earth’s energy balance composed of ?

A

The incoming energy from the sun that’s splits into: reflected energy from the atmosphere, energy reflected from Earth, energy that was absorbed in the water released in radiated heat that can also be returned to Earth.

51
Q

What is Earth’s energy balance composed of?

A

The incoming energy from the sun that’s splits into: reflected energy from the atmosphere, energy reflected from Earth, energy that was absorbed in the water released in radiated heat that can also be returned to Earth.

GEOG272 (9 decks)

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