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Weather and Climate > Radiation > Flashcards

Radiation Flashcards

1
Q

name 3 things that happens to the solar radiation as its transmitted through earths atmosphere between the atmosphere and ground?

A

scattering

reflection and absoption of short wave radiation

emittance of long wave radiation

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2
Q

what is solar energy?

A

radiant light and heat energy emitted by the sun

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3
Q

What is short wave radiation?

A

UV - visible light

shorter wavelength

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4
Q

how much energy does SWL have?

A

lots

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5
Q

where does SWL come from?

A

The sun emits SWL radiation which is directly diffused/ scattered , reflected or absorbed

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6
Q

What is Long wave radiation?

A

infrared

longer wavelength

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7
Q

how much energy does LW radiation have?

A

less energy than SW

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8
Q

Where does LW radiation come from?

A

the ground heats up and re emits as long wave radiation as infrared

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9
Q

define albedo

A

the reflectivity of a material

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10
Q

how can albedo be calculated?

A

ratio of outgoing radiation and incoming SW radiation

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11
Q

what does it mean by reflected?

A

bounces off something and goes in another direction eg a tree

everything we see has light reflecting off it - thats why we cant see very well in dark room

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12
Q

what things cause reflection

A

reflection by ground surface

reflected by clouds

diffuse reflection

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13
Q

what type of reflection do natural surfaces get?

A

diffuse reflection as they are rough and energy scattered away from surface

(smooth surfaces have purer reflection when angle of incidence approaches angle of reflection)

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14
Q

what is the albdeo of a perfectly black surface?

A

zero
no reflection
absorbing

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15
Q

what is the albedo of a perfectly white surface?

A

1
complete reflection
no absorbing

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16
Q

do smooth surfaces increase or decrease albedo ?

A 
increase albedo
(rough surfaces decrease albedo)
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17
Q

how many grey tones can the eye detect?

A

20

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18
Q

When will liquid water have a high albedo?

A

when suns angle is very low eg sunrise
the angle is low and radiation will be reflected by water
this is why high latiudes reflect more sola radiation (also due to albedo)

19
Q

When will liquid water have a low albedo?

A

when sun is above horizon

it absorbs SR

20
Q

snow and cloud albedo??

A

high albedo as white and smooth (clouds vary)

0.4-0.9

21
Q

sand, dry soil and ice albedi???

A

darker surface and less smooth so lower albedo than snow

0.3-0.4

22
Q

vegetation and water albedo???

A

darker and rough surfaces so have low albedo

0.0 - 0.25

23
Q

what places have the highest albedo?

A

snow covered areas like antarctica

cloud cover

(high albedo correlates to places with highest Sw radiation being reflected back to space)

24
Q

what could scatter radiation into atmosphere ?

A

gases
particulates - dust
water droplets - clouds

25
Q

what is diffuse insolation?

A

shortwave radiation that has been scattered without altering wave length

26
Q

what % of reflectivity or albedo does scattering account for?

A

7%

depends on size of molecules being scattered

27
Q

what determines the colour of light?

A

the wavelength

28
Q

Define scattering

A

the process which electromagnetic radiation or particles are deflected or diffused

it depends upon the size of molecules/particles it encounters

29
Q

what happends when light encounters molecules in atmosphere ?

A 
Shorter WL (blue) - more scattering
Longer WL (red) - less scattering

this is called rayleigh scattering

30
Q

define rayleigh scattering?

A

when particle sizes are smaller than the wavelength of incident energy

scattering by small particles

31
Q

define mie scattering?

A

particles and wavelengths around the same size

larger particles >0.5 um
eg smoke paricles/ very fine dust

scattered equally though in a more forward direction

atmosphere appears white

32
Q

define non-selective scattering

A

associated with large particles all wavelengths affected equally
eg raindrops/cloud droplets/ice

33
Q

what wavelength is scatterred more? red or blue?

A

shorter blue wavelength scattered more than long red wavelength

(alost 10 times more)

scattering creates blue skies and red sunsets

34
Q

what 2 things absorbs solar output?

A

clouds

gases and dust in atmosphere

35
Q

what makes up a hazy sunshine?

A

mie scattering - white around sun

rayleigh scattering - blue sky away from sun

36
Q

what happens to the fraction of energy that makes it to the surface?

A

its radiated back to space
(longwave radiation)

if it wasnt radiated back to space then the earth would warm

energy balance important but earth is warming now so energy isnt balanced

37
Q

how much insolation is lost back to space as shortwave radiation?

A

~31% reflected

meaning ~69% absorbed

38
Q

what is the average planetary albedo?

A

~31%

this is high as moons albedo is 8%

39
Q

how much LW energy is radiated back to space?

A

~69%

40
Q

Name 3 ways insolation is remitted?

A

absorbed by ground and reemitted as longwave radiation

emitted from ground directly to space

emitted from ground and absorbed by atmosphere, then remmitted by atmosphere to space or the ground

41
Q

what regions radiate the most longwave radiation??

A

hot locations

they receive higher input of SW radiation

42
Q

describe 3 latitudinal variations in the energy balance?

A

more energy absorbed in tropics

more reflection emitted in polar regions

energy into earths surface balances energy out of earth ~36%

43
Q

what location receives the most energy?

A

tropics

desert areas have less cloud so less scattering and lots of radiation reaches the surface

over jungle theres clouds so more scattering and less radiation reaches the ground

44
Q

what location receives the least energy?

A

poles

greater sun angle, greater distance through atmosphere, more scattering, greater seasonal variations insolation.

Weather and Climate (4 decks)

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