Test 2 Flashcards

1
Q

Describe what Raindrop formation requires

A

-Condensation nuclei

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2
Q

What are the two processes for droplet growth

A
  1. Collision - coalescence process

2. Ice-Crystal (bergeron) process

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3
Q

Explain collision - coalescence

A
  • need different droplet sizes
  • Terminal velocity greater for larger rain drops
  • large drops overtake and collide with small drops

This is the dominant precipitation mechanism in warm phase of clouds

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4
Q

What effects collision-coalescence precipitation production?

A
  1. Liquid water content (LWC)
  2. Range of droplet size
  3. cloud thickness
  4. updraft speed
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5
Q

Where is the cold section in a typical cumulonimbus could

A

Top

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6
Q

What is the ice-crystal (bergeron) process

A
  • Saturation vapor pressure over ice surface < over liquid surface
  • Vapor pressure difference causes the movement of water vapor molecules from liquid to ice surface
  • Ice crystals grow at the expense of liquid droplets.
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7
Q

What is secondary ice formation

A

ice crystals grow, fall, collide with super cooled droplets, which freeze on contact (accretion).

This creates larger ice crystals (graupel) which ___Missing____

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8
Q

What is the dominant preticipation formation in warm clouds

A

Collision and coalescense

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9
Q

List the types of precipitation

A
  1. Rain
  2. Virga
  3. Snow
  4. Fallstreaks
  5. Dendrite snowflakes
  6. Hail
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10
Q

What is virga

A

when rain droplets fall but evaporate before hitting the ground.

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11
Q

What is hail

A

pieces of ice

-form in cumulonibus clouds

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12
Q

List other types of precipitation

A
  1. sleet
  2. freezing rain
  3. Rime
  4. Snow grains
  5. snow pellets
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13
Q

What is sleet

A

Falling snowflakes partly melts in warmer air then falls through cold (<0C) surface layer of air and refreezes to ice pellet

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14
Q

What is freezing rain

A

Its the same as sleet but the cold layer is too thin. ____Missing____

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15
Q

What is Atmospheric Pressure?

A

Weight of air above a given height

  • Obeys the gas law
  • decreases with height (rate varies though)
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16
Q

what is variation in atmospheric pressure based on?

A

high and low pressure areas

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17
Q

What is the pressure gradient

A

horizontal pressure differences

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18
Q

What causes wind?

A

The pressure gradient

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19
Q

List four primary ways in which

clouds form.

A
  1. surface heating and free convection
  2. uplift along topography
  3. widespread ascent due to the fl owing together (convergence)
    of surface air
  4. uplift along weather fronts
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20
Q

Explain why rain shadows form
on the downwind (leeward) side
of mountains.

A

by forcing air to rise along their windward
slopes. -> the windward side of mountains tends to be “wet.” As air descends and warms along the leeward side, there is less likelihood of clouds and precipitation. Thus, the leeward (downwind) side of mountains tends to be “dry.”

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21
Q

What is the primary difference
between a cloud droplet and a
raindrop?

A

Rain drops -> about 2 mm and have enough mass to fall to the ground

Cloud droplet -> about 0.02 mm and do not have enough mass to fall to the ground

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22
Q

when does warm, moist air rise?

A

in conditionally unstable atmosphere

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23
Q

What is Rising air due to?

A
  1. Strong surface heating
  2. topographical forcing
  3. Frontal lifting
  4. Convergence of surface air
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24
Q

Where do ordinary cell (air mass) Thunderstorms form?

A

where there is limited vertical wind shear (wind speed/direction do not abruptly change with height)

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25
Q

Are Ordinary cell (air mass) Thunderstorms Isolated thunderstorm and not severe?

A

Yes

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26
Q

Are Ordinary cell (air mass) Thunderstorms short lived?

A

Yes (45-60 min)

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27
Q

What is the 3 stage life cycle of Ordinary cell (air mass) Thunderstorms?

A
  1. Cumulus or growth
  2. Mature
  3. Dissipating
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28
Q

What does entrainment mean?

A

Dry outside air drawn in side and top

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29
Q

What are downdrafts?

A

Cool dense air descends

30
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is the air rising or falling?

A

rising

31
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is inside the cloud warmer or colder then surroundings? why or why not?

A

Warmer.

Condensation → release of latent heat, inside cloud warmer than surroundings

32
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is the cloud dominated by updrafts or down drafts?

A

updrafts

transports warm and moist air upward

33
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is entrainment occuring?

A

yes. Dry outside air drawn in on the side and top

34
Q

When Entrained air evaporates rain drops does the air warm or cool?

A

cools

35
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is the cool air ascending or descending?

A

descending (downdraft)

36
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is rain reaching the ground?

A

no

37
Q

In the cumulus stage of Ordinary cell (air mass) Thunderstorms is lightning and thunder occurring?

A

no

38
Q

Which stage has the most intense stage in a Ordinary cell (air mass) Thunderstorms

A

The mature stage

39
Q

Are strong downdrafts or updrafts occurring in the middle of clouds in the mature stage of a ordinary cell (air mass) Thunderstorms

A

both

40
Q

in the mature stage of a ordinary cell (air mass) Thunderstorms how high does the cloud go? at the top what direction is the cloud spreading?

A

Top reaches tropopause/ stratosphere (stable layer - no vertical motion and strong winds spread top horizontally)

41
Q

in the mature stage of a ordinary cell (air mass) Thunderstorms what does the cloud look like?

A

an anvil

42
Q

in the mature stage of a ordinary cell (air mass) Thunderstorm is lightning/thunder occurring?

A

Yes

43
Q

in the mature stage of a ordinary cell (air mass) Thunderstorm are ice and water present?

A

yes

44
Q

in the mature stage of a ordinary cell (air mass) Thunderstorm is precipitation reaching the surface?

A

yes

45
Q

At what stage of a ordinary cell (air mass) Thunderstorm does the gust front occur?

A

Mature

46
Q

What is a gust front?

A

Cold downdraft reaches surface  spread horizontally

47
Q

Does a gust front enhance updraft or downdraft?

A

enhances a clouds updraft

48
Q

Is the dissipating stage of a ordinary cell (air mass) Thunderstorm dominated by downdrafts or updrafts?

A

downdrafts

49
Q

In the dissipating stage of a ordinary cell (air mass) Thunderstorm is there precipitation

A

yes but its light

50
Q

What are Multi-Cell Thunderstorm?

A

Series of connected storms (complex), each could be in a different stage of its life cycle

51
Q

Where do Multi-Cell Thunderstorms form?

A

Form in the region of strong wind shear

-Strong wind shear tilts storm cell, consequently updraft rides over cold downdraft

52
Q

in a Multi-Cell Thunderstorms is the storm life extended? how?

A

Yes. The cold downdrafts do not cut off updrafts

53
Q

Where is lightning traveling 80% of the time?

A

within clouds and between clouds

54
Q

where is lightning traveling 20% of the time?

A

to the ground

55
Q

How much can lighting heat the air around it? what happens when this happens?

A

A lot. considerably more then the sun. when this happens it creates a shock wave (thunder)

56
Q

How can you estimate the distance that lightning is away from you?

A

count number of seconds after lightning until thunder (sound travels 1 km in 3 seconds, light: ~300,000 km/sec)

57
Q

Is charge distribution well understood?

A

no

58
Q

What is the leading theory on charge distribution?

A

Leading theories propose that charge separation is created when hail and graupel (soft hail) fall through supercooled drops and ice crystals.

59
Q

In the leading theory on charge distribution are positive charges found at the top or bottom of the cloud? is this due to small or large ice particles?

A

top and due to small particles being forced up

60
Q

In the leading theory on charge distribution. why does lightning happen?

A

negative charges induce positive charges on the ground. the higher the object the more charge it has. at the critical point the cloud will try to discharge and if the charge difference is large enough lightning occurs

61
Q

How does lightning get from the cloud to the ground?

A

A step leader (electricity from the cloud) that is visible moves towards the ground. then the positive charges on the ground move up to meet it

62
Q

What is a return stroke?

A

(+) charge surges upwards to cloud
Return Stroke: 1/10,000 of a second (too fast to see motion)
Repeats (typically 3-4 repeats) in same path

63
Q

What are the steps of lightning

A
  1. Step leader forms
  2. ground charges rise to meet it
  3. The return stroke occurs
64
Q

How do water droplets form in warm cumulus clouds?

A

A cloud droplet rises due to strong updraft
Smaller droplet rises quickly and collides  1 mm

  • Updraft force = downdraft -> suspend until it grows little bigger
  • Once fall velocity > updraft > the drop descends
  • The droplet grows by collision and coalescence 5 mm
65
Q

What is the Ice-crystal (Bergeron) process

A

Dominant precipitation formation process in cold clouds
Ice crystals grow at the expense of liquid droplets
Difference in saturation vapor pressure between ice crystals and liquid drops results in diffusion (move) of water vapor molecules from liquid to ice crystals

66
Q

Explain Hail

A

Ice the size of small peas to golf balls. forms in cumulonimbus clouds. hail grows by accretion ( collisions with super cooled droplets that freeze. ) Needs strong updrafts inside of clouds

67
Q

What direction of variations in pressure drive meteorological phenomenon

A

horizontal

68
Q

What creates wind

A

The pressure gradient

69
Q

What are Geostrophic winds

A

straight line

70
Q

What are Gradient winds

A

curved