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Intro to Weather and Climate (MEA 130) > Chapter Five - Test Two > Flashcards

Chapter Five - Test Two Flashcards

1
Q

During clear, calm nights:
The ground cools very rapidly thru ____

The air that comes in contact with the ground cools thru ____.

A

radiational cooling; conduction

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2
Q

If the T cools down to Td (i.e. RH = 100%), ____ occurs.

A

saturation

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3
Q

If the T (which equals Td)) are greater than 32oF :

The water vapor molecules will condense into liquid water forming visible droplets on objects (i.e. grass, car) called ____.

A

Dew Formation; dew

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4
Q

If the T (which equals Td)) are less than 32oF :

The water vapor molecules deposit directly into ____

A

(White) Frost Formation; frost

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5
Q

Nights that favor dew/frost formation are those that experience “maximum radiational cooling” (discussed earlier):

A
  • Clear skies
  • Calm Winds
  • Long nights
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6
Q

Neither dew nor frost “fall” from the sky, rather they are formed ____ (in place).

A

insitu

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7
Q

There is a less know phenomenon called “____”, which occurs when dew first forms thru condensation and then later freezes into tiny ice spheres.

A

frozen dew

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8
Q

visible aggregate (collection) of liquid water droplets and/or ice crystals suspended in the atmosphere

A

clouds

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9
Q

when an air parcel rises, it cools adiabatically and if the parcel’s T cools down to the Td, saturation and subsequently condensation occurs and:

A

a cloud is formed, beginning at the LCL

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10
Q

Just as dew/frost needs a surface to form on (i.e. grass), there must be a surface upon which water vapor can condense (deposit) in the air:

A

Cloud Condensation Nuclei (CCN)

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11
Q

Growth of Cloud Droplets

As the water vapor molecules cool, they:

A
  • lose energy,
  • move more slowly
    until they eventually adhere to the CCN.

Picture the water vapor molecules “getting tired” and needing a place to rest.

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12
Q

Because CCN are so small and light

A

they can remain suspended for weeks

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13
Q

Even “clean” air contains over: ____ CCN/cm ^3

A

1,000

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14
Q

CCN enter the atmosphere through a variety of pathways, both:

A

Natural: dust, salt spray, volcanic ash, fires, pollen

Anthropogenic: sulfates, nitrates from fossil fuel burning (acid rain), fugitive dust

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15
Q

Some CCN are:

A

Hygroscopic (water seeking)

Hydrophobic (water repelling)

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16
Q

Cloud Classification

Classification developed around 1800 by ____ on the basis of:

A

Luke Howard

Form and Height: Combinations of these forms and height give us ten major cloud types

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17
Q

Cloud Forms:

A

cirrus form - (Latin for wisp)
cumulus form - (Latin for heap)
stratus form - (Latin for Layer)
nimbus form - (Latin for rain)

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18
Q

Cloud Heights:

A

High - ( > 6 km)
Middle - (2 to 6 km)
Low - ( 6 km)

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19
Q

High Clouds (> 6 km)

A
  • thin (tens of meters thick)
  • comprised solely of ice crystals
  • non-precipitating
  • form in slowly rising
    Cirrus (Ci), Cirrostratus (Cs), Cirrocumulus (Cc)
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20
Q

Cirrus (Ci) (Figure 5.3a)

A
  • most common high cloud

- called “Mare’s Tails”

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21
Q

Cirrostratus (Cs) (Figure 5.3b)

A
  • often produce Halo around sun or moon, which is due to the refraction of light by ice crystals
  • often precedes precipitation
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22
Q

Cirrocumulus (Cc) (Figure 5.3c)

A
  • form in a more turbulent environment

- “Mackerel Sky”

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23
Q

Middle Clouds (2 - 6 km)

A
  • thicker (hundreds of meters thick)
  • comprised mostly of liq. Droplets w/some ice crystals
  • also non-precipitating
    Altocumulus (Ac) , Altostratus (As)
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24
Q

Altocumulus (Ac) (Figure 5.4a)

A
  • often occur in large patches

- bases are darker

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25
Q

Altostratus (As) (Figure 5.4b)

A
  • no definite configuration (formless)

- sun/moon barely visible

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26
Q

Low Clouds (

A
  • thick (thousands of meters thick)
  • comprised mostly of liquid droplets with some ice crystals
  • some types produce precipitation
    Stratus (St), Stratocumulus (Sc), Nimbostratus (Ns)
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27
Q

Stratus (St)

A
  • resembles a fog that doesn’t reach the surface
  • sun is not visible
  • can produce drizzle
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28
Q

Stratocumulus (Sc)

A
  • appear in long parallel rows or patches
  • rarely precipitate
  • 1 km thick
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29
Q

Nimbostratus (Ns) (Figure 5.5)

A
  • produces continuous, generally light precipitation
  • completely blocks out the sun/moon
  • 2 to 4 km thick
    90% of world’s snow falls out of this cloud
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30
Q

Clouds with Vertical Development (2 km to > 6 km)

A
  • very thick (tens of thousands of meters thick)
  • comprised of liquid droplets and ice crystals
  • associated with unstable air
  • some produce precipitation
    Cumulus (Cu), Cumulonimbus (Cb)
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31
Q

Cumulus (Cu) (Figure 5.6)

A
  • 1 to 5 km thick
  • mostly liquid water
  • resemble cotton balls
  • dark, flat bases (LCL)
  • “Fair weather” clouds
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32
Q

Cumulonimbus (Cb) (Figure 5.7)

A
  • 5 to 20 km thick
  • thunderstorm cloud
  • very strong updrafts, downdrafts
  • produce intense rain
  • produce lightning and thunder, hail and tornadoes
33
Q

Lenticular (Lens) Clouds (Figures 5.8)

A
  • lens shape cloud that forms over and to the leeward side of the tall mountain ranges
34
Q

Mammatus (Mammary) Clouds

A
  • Form in severe thunderstorms
35
Q

Anthropogenic Clouds

A

Contrail Clouds (Figure 5.A,B)

  • Cirrus-like clouds that often form on exhaust of high-flying jets
36
Q

Defined as a cloud with its base at or near the surface:

A

Fog; restricts visibility to 1 km or less

37
Q

Produced when cooling of the air reduces T to Td, hence saturation and condensation occurs.

A

Fogs Formed by Cooling

Radiation, Advection

38
Q

Radiation Fog

A

`Occurs at Night, over Land: when radiational cooling reduces T to Td

  • generally associated with High Pressure
  • light winds –> Maximum Radiational
  • clear skies –> Cooling
  • occurs more often in winter (long nights)
39
Q

Advection Fog (Fig. 5.10)

A

occurs when warm, moist air is advected over a cooler surface reducing T to Td

  • unlike radiation fog, advection fog requires the Movement of air
  • San Francisco’s golden gate
  • warm air moving over snow cover
40
Q

Fogs Formed by Evaporation

A

Steam Fog (Fig. 5.11)

41
Q

Steam Fog (Fig. 5.11)

A

occurs when cold air moves over warm water

  • the air immediately over the water surface first warms and gathers water vapor through Evaporation
  • it then rises (because it’s less dense) allowing T will cool to Td
  • Occurs over ponds/lakes in autumn and winter
42
Q

Average annual frequency of days with heavy fog

A

Pacific Coast States (> 40 days) Advection
New England Coast (> 40 days) Advection
Appalachian Mtns.(> 40 days) Radiation (valley)
Raleigh (25-30 days) Radiation (valley)

43
Q

Satellites in Weather Forecasting

A

GOES (Geostationary Operational Environmental Satellite)

POES (Polar Operational Environmental Satellite)

44
Q

GOES (Geostationary Operational Environmental Satellite)

A
  • orbit above the equator at 36,000 km at the same rate the earth rotates (Fig 12.17b)
  • remain stationary above a fixed location
  • allows for continuous observation above a location
  • limited resolution
45
Q

POES (Polar Operational Environmental Satellite)

A
  • orbit north-south at less than 1,000 km passing over both poles allowing the earth to rotate beneath (Fig. 12.17a)
  • allows for complete coverage of earth, twice per day
  • better resolution
46
Q

What Weather Satellites Provide

A
  • Visible images (Fig. 12.18)
  • IR images (fig. 12.19)
  • Water vapor images (fig. 12.20)
47
Q

Though necessary, the processes of condensation is entirely too ____ to produce precipitation alone. Even under the most “ideal” conditions, it would take several days to produce a small ____ solely thru condensation

A

slow, rain drop

48
Q

Cloud Drop

A

(r= 10µ)

49
Q

Rain Drop

A

(r= 1000µ)

50
Q

A cloud droplet must increase its volume by ____ in order to grow to the size of a rain drop.
- and condensation alone cannot do this.

A

1 million or (1 x10^6)

51
Q

Clouds can form and precipitate in less than hour through two processes:

A

1) Bergeron (ice Crystals) Process

2) Collision- Coalescence Process

52
Q

Precipitation from Cold Clouds:

A

The Bergeron Process

53
Q

The Bergeron Process
Most clouds (outside of tropical latitudes) form in areas of the ____ where temperatures are well below freezing.
Surprisingly: these clouds are mostly comprised of ____ droplets, despite the fact that their temp. is well below freezing!

Such droplets are called:

A

troposphere; liquid

Super Cooled Cloud Droplets

54
Q

The Bergeron Process
In order for deposition to take place the water vapor molecules must come in contact with unique particles that have a ____ shape.

Such particles are called: ____

A

crystal lattice

Ice Crystal or Deposition Nuclei

  • that act as nuclei for the formation of ice crystals through deposition.
55
Q

The Bergeron Process
The need for a deposition nuclei to initiate deposition is similar to the need of CCN to initiate condensation.
However, there are far ____ deposition nuclei than CCN
- 1:____ ratio

So even in cold clouds, the number of liquid water cloud droplets greatly exceeds the number of ice crystals, as a result:
- Millions of liquid droplets will ____ each ice crystal.

A

fewer; 1,000,000; surround

56
Q

The Bergeron Process
Because of a subtle difference in the saturation mixing ratio (MRs) over an ice surface compared to that of a liquid surface, water vapor molecules will: ____ away from the liquid droplet, and
____ onto the ice crystal

A

Evaporate; Deposit

57
Q

Ice crystals grow at the expense of the liquid water droplets. This growth process is called the:

A

Bergeron Process

after the Swedish meteorologist that discovered it (Fig. 5.14).

58
Q

As the ice crystals grow larger they eventually fall where:

A
  • They either reach the ground intact as snowflakes, or

- they melt and reach the surface as raindrops.

59
Q

Precipitation from Warm Clouds:

A

The Collision - Coalescence Process

60
Q

The average cloud droplet has a diameter of:

A

20 µ (0.02 mm)

61
Q

Cloud droplet sizes vary considerably, due in part to the size and type (hydrophobic, hygroscopic) of their ____

As a result, the variably sized cloud drops have variable:
Fall (or Terminal) ____

Defined as the point at which air resistance = ____ force; so that the acceleration = 0; and the drop falls at a constant velocity (Table 5.3).

A

CCN; Velocities; gravitational

62
Q

Large drops fall faster and “overtake” small drops where they:

A

Collide and coalesce (combine)

63
Q

After coalescing, cloud drops are larger, fall faster, further increasing the # of collisions, until, after ____ or so collisions, they are large enough to fall to the ground as a ____ drop (Fig. 5.15).

A

a million; rain

64
Q

Rain drops resemble what shape?

A

Hamburger bun

65
Q

Two factors important to Collision Coalescence Process:

A

1) Cloud Thickness

2) Cloud Updraft Strength

66
Q

Thick clouds with strong ___ can produce larger drops and more intense than thin clouds with weak ones

A

updrafts

67
Q

A warm Stratus Cloud is typically:

  • Thin (~1000 m thick) and
  • has weak updrafts (
A

A stratus cloud droplet would spend ~ 10-15 min in the cloud and at most grow to ~ 500µ (the size of drizzle).

68
Q

A warm Cumulus Cloud is typically:
- thick (>5000 meters)
- Strong updrafts (> 0.6 m/s)
Therefore:

A

A cumulus cloud droplet could spend ~ 1-2 hours in the cloud and be able to grow to 5000µ (the size of a large raindrop).

69
Q

While falling, the raindrops/snowflakes are often altered by the atmospheric conditions encountered beneath the cloud. (Table 5.4)
They can:

A
  • change form (i.e. snow to rain)
  • evaporate resulting in a phenomenon called:
    Virga (Latin for streak) (fig. 5.17)
70
Q

Rain (500µ

A

either nimbostratus or cumulonimbus clouds

71
Q

Nimbostratus clouds produce ____ rain, characterized by:

A

stratiform

  • continuous (hours to day)
  • light rates (0.1- 0.2 inches per hour)
  • often called “overrunning precipitation”
72
Q

Cumulonimbus clouds produce ____ rain, characterized by:

A

convective

  • generally brief (minutes to hour)
  • intense rates (1-2 inches per hour)
73
Q

Snow (Fig. 5.16b)

A

Results if the temperature remains near or below freezing between the cloud base and the surface.
Six-sided ice-crystals (Fig. 5.18)
- Small, dry powdery snowflakes are associated w/T

74
Q

Sleet (Fig. 5.16c, 5.19) results, if while falling, the snow first encounters a ____ Layer in which melting occurs and then encounters a:
Deep ____ Layer
above the surface in which complete freezing recurs before the precipitation reaches the surface.

A

warm (T > 32º), cold (T

75
Q

____ (Freezing Rain) (Fig. 5.16d, 5.20) results, if while falling, the snow first encounters a Warm Layer (T > 32º) in which melting occurs and then encounters a:
____ Cold Layer (T

A

Glaze, Shallow; surface

  • adheres to trees/ power lines (fig. 5.20)
  • can cause extensive damage
76
Q

Standard Rain Gauge (Fig. 5. 25b)

A

Funnel shaped collector has an opening 10x wider than tube to allow for greater precision

  • Can measure to nearest 0.01 inches
    • Any amount less called a Trace
      • Disadvantage: needs a person to record data
77
Q

Standard Tipping Bucket (Fig. 5.25c)

A

A thimble-sized bucket fills and tips over for every 0.01” which creates an electrical signal that can be recorded
- Can be used remotely

78
Q

Snow Gauge

A

A Standard Rain Gauge that has been modified with wind screens (Fig. 5.26) to ensure accurate collection. The snow is then melted to get: Liquid Equivalent precipitation

79
Q

RADAR:

Each RADAR unit consists of a:
Transmitter:
when the energy encounters an object, a small fraction of the energy is reflected back to the:
Receiver:

A

Radio Detection And Ranging (Figs. 5.27, 10.27,10.28)

emits powerful pulses of energy;
which amplifies and displays the signal on a screen as an echo providing precipitation:

Intro to Weather and Climate (MEA 130) (9 decks)

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