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Weather and Climate > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Water is, near the surface, the atmosphere’s most abundant __________

A

trace gas

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2
Q

Evaporation

A

The process by which water is converted from liquid form into its gaseous state, water vapor

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3
Q

When the number of molecules leaving the liquid is in equilibrium with the number condensing, the air above the surface is ____________

A

saturated - the rate of return of water molecules is exactly equal to the rate of escape of molecules from the water

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4
Q

Why do we need to measure the amount of water vapor in the atmosphere?

A

The change of phase of water is an important energy source for storms, atmospheric circulation patterns, and cloud and precipitation formation

Water vapor is the source of all clouds and precipitation. The potential for cloud formation and dissipation depends on the amount of water vapor in the atmosphere

The amount of water in the atmosphere determines the rate of evaporation. Rates of evaporation are important to weather and many forms of plant and animal life, including humans

Water vapor is a principal absorber of longwave radiant energy. It is the most important greenhouse gas

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5
Q

Mixing ratio

A

Ratio of the wight of water vapor to the weight of the other molecules in a given volume of air

The unit of mixing ratio is grams of water vapor per kilogram of dry air

Mixing ratio is an absolute measure of water vapor

Typical values of the mixing ratio near the surface range between less than 1 gram per kilogram in polar regions to more than 15 grams per kilogram in the tropical regions

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6
Q

Evaporating water into the volume ____________ the mixing ratio

A

increases

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7
Q

The pressure the water molecules exert is another useful method of representing the amount of water vapor in the atmosphere. The pressure caused by these water vapor molecules is called the ____________

A

vapor pressure

*expressed in millibars (mb)

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8
Q

The vapor pressure attributable to water vapor alone is never more than about _______________

A

4% of 1000mb

or 40mb

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9
Q

Increasing the air temperature will _________ vapor pressure

A

increase

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10
Q

When air is saturated, the pressure exerted by the water vapor molecules is called the __________________

A

saturation vapor pressure

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11
Q

Most important fact about saturation vapor pressure:

A

It increases rapidly as the temperature increases - as the temp of water increases, the number of molecules with enough kinetic energy to evaporate from the water surface increases.

Increasing the temperature also increases the numbeer and speed of the water molecules in the vapor phase

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12
Q

It is more accurate to say:

A

a saturated parcel of warm air will contain many more water vapor molecules than a saturated parcel of cooler air

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13
Q

Saturation ratio

A

The ratio of the actual vapor pressure exerted by molecules of water vapor versus the saturation vapor pressure at the same temperature indicates just how close the air is to saturation

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14
Q

saturation ratio x 100% =

A

relative humidity

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15
Q

Relative humidity

A

Describes how far the air is from saturation

saturated air ==> relative humidity of 100% because vapor pressure equals the saturation vapor pressure

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16
Q

A relative humididity of 50% tells us that that the vapor pressure is _______________________

A

half that required for saturation

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17
Q

Water evaporates more slowly in air that has a ________________

A

high relative humditiy

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18
Q

Water evaporates more quickly in air that has a _________________

A

low relative humidity

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19
Q

Relative humidity is more generally an important indicator of ________________________

A

the rate of moisture and heat loss by plants and animals

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20
Q

Decrease in temperature results in an ___________ in the relative humidity

A

increase

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21
Q

Increasing the temperature ____________ the relative humidity

A

decreases

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22
Q

Condensed water is called _________

A

dew

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23
Q

Dew point

A

The temperature to which air must be cooled to become saturated without changing the pressure

*determined by keeping the pressure fixed because changing the pressure affects the vapor pressure and therefore the temperature at which saturation occurs

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24
Q

The closer the dew point is to the air temperature =>

A

the closer the air is to saturation

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25
Q

The temperature difference between the air and the dew point is called the ________________

A

dew point depression

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26
Q

The ice crystals that form are called _____________

A

frost

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27
Q

The temperature to which air must be cooled at a constant pressure to cause frost to form is called the ___________

A

frost point

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28
Q

Dew may form and then freeze if the temperature falls below freezing, forming ______________

A

frozen dew

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29
Q

Rime

A

opaque deposit of ice formed by the rapid freezing of water drops as they collide with an object at or below freezing

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30
Q

Clouds are composed of:

A

tiny 20-micron-sized particles of liquid water called cloud droplets and particles of ice called ice crystals

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31
Q

The greater the concentration of salt =>

A

the more the rate of evaporation is reduced

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32
Q

Solute effect

A

The ability of dissolved salt to hold onto water molecules

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33
Q

Curvature effect

A

The smaller the drop, the more curved the surface, reducing the number of neighbors for each water molecule at the surface.

This curature effect makes it easier for small drops to evaporate

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34
Q

Supersaturation`

A

The relative humidity must be higher than 100%

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35
Q

Nucleation

A

The initial formation of a cloud droplet around any time of particle

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36
Q

Two types of nucleation:

A
  1. homogeneous nucleation
  2. heterogeneous nucleation
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37
Q

Homogeneous nucleation

A

The droplet is formed only by water molecules

Requires that enough water molecules bond together to form a cluster, or particle, that then acts as a nucleus for fututher condensation

Occurs at temperatures colder than -40 degrees celsisus

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38
Q

Heterogeneous nucleation

A

Occurs when small, nonwater particles serve as sites for cloud droplet formation

These particles are usually areosols

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39
Q

The areosols that assist in forming liquid droplets are called _______________

A

condensation nuclei

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40
Q

There are two types of condensation nuclei:

A
  1. hygroscopic
  2. hydrophobic
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41
Q

Hygroscopic nuclei

A

dissolve in water

Droplet formation can occur on hygroscopic nuclei even when the relative humidity is below 100% because the solute effect reduces the rate of evaporation

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42
Q

Hydrophobic nuclei

A

Do not dissolve in water

Hydrophobic nuclei resist condensation but can form droplets when relative humidities are near 100%

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43
Q

____________, the particles around which the ice crystals form, are important in the beinning stages of ice crystal formation

A

Ice nuclei

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44
Q

Ice particles can form in 4 ways:

A
  1. Deposition nucleation
  2. Freezing nucleation
  3. immersion nucleation
  4. contact nucleation
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45
Q

Deposition nucleation

A

Ice forms from vapor by deposition onto the ice nucleus when the air is supersaturated with respect to ice

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46
Q

Liquid water at a temperature below 0 degrees Celsisus is referred to as ____________________

A

supercooled water

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47
Q

Freezing nucleation

A

The process by which a supercooled drop freezes without the aid of a nonwater particle

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48
Q

0 degrees Celsisus is more accurately called the ________________, not the freezing point, of water

A

melting point

49
Q

Immersion nucleation

A

The nucleus is submerged in a liquid drop

50
Q

Lice nuclei may also collide with supercooled drops. The drop freezes immediately on contact with the ice. This is referred to as ___________________

A

contact nucleation

51
Q

a cloud at the ground

A

fog

52
Q

4 different types of fog

A
  1. Radiation fog
  2. advection fog
  3. evaporation fog
  4. upslope fog
53
Q

Radiation fogs

A

Tend to develop on clear nights

Light winds required because they can gently mix moist air near the ground

If the dew point temperature is approximately 8 degrees Celsisus below the air temp at sunset and if the winds are predicted to be less than 9 kilometers per hour, there is a good chance that radiation fog will form during the night

54
Q

Advection fog

A

When warm air is advected over a cold surface, the air near the ground cools because of energy exchanges with the surface. The relative humidity increases, and an advection fog may form

55
Q

Evaporation fogs

A

Occur in the vicinity of warm fronts and are sometimes called frontal fogs

These fogs form when water evaporate from rain that falls from warmer air above the ground into cold air near the surface

Occur only after it has been raining

56
Q

Steam fog

A

Evaporation fog over a lake gives the appearence of steam rising out of the water and sometimes referred to as steam fog

57
Q

Upslope fog

A

As the air rises over a mountain barrier, it expands and cools, and the relative humidity rises. If the air becomes saturated, an upslope fog forms

58
Q

Orographic lifting

A

The air cannot go through the mountain, and so it flows over the mountain

59
Q

Frontal lifting

A

Occurs when less dense warm air is forced to rise over the cooler, denser air

Frontal lifting is common in winter

60
Q

Convection

A

An important lifting mechanism in summer

Solar energy passes through the atmosphere and heats the surface. The air near the surface warms, becomes less dense than the air around it, and rises

61
Q

Convergence

A

Occurs when air near the surface flows together from different directions

62
Q

Divergence

A

The opposite of convergence - which is the horizontal spreading out of air

63
Q

In each case o flifting, the rising air creates an ____________,

A

updraft

the updraft keeps the cloud particles suspended in mid air despite the force of gravity that acts to bring them to the ground

64
Q

Saturated Parcel of air

A

One in which the air contains the maximum amount of water vapor possible; its relative humidity is therefore 100%

65
Q

Saturated adiabatic lapse rate

A

The rate that the rising saturated air parcel cools

66
Q

Lifting condensation level (LCL)

A

The height at which water vapor in a rising parcel of air starts condensing. The bottoms of puffy flouds on sunny days are at the altitude of the LCL.

67
Q

Ascending parcels that are saturated cool _________ than do unsaturated parcels

A

less quickly

68
Q

The case where saturated air parcels are unstable, but unsaturated air parcels are stable, is called a ______________________

A

conditionally unstable environment

69
Q

A conditionally unstable enviornment exists when its lapse rate is in between:

A

the saturated adiabactic lapse rate of about 6 degrees Celsius per kilometer and the dry adiabatic lapse rate of 10 degrees Celsius per kilometer

70
Q

Less than saturated adiabatic lapse rate

A

Environment is absolutely stable

No parcels keep rising

71
Q

Greater than dry adiabatic lapse rate

A

Environment is absolutely unstable

All parcels keep rising

72
Q

Less than dry adiabatic lapse rate and greater than saturated

A

Environment is conditionally unstable

Only saturated parcels keep rising

73
Q

Layered clouds

A

Much wider than they are tall

Flat bases and tops and can extend from horizon to horizon

74
Q

Convective clouds

A

As tall, or taller, than they are wide

These clouds look lumpy and piled up

75
Q

Stratus clouds

A

Are fog that hovers just above (rathern than on) the ground

Appear light to dark grey in color and cover the sky

76
Q

Stratocumulus clouds

A

Low-lying clouds that cover the sky and appear white to gray in color

They are a combinaition of layered and convective cloud types

Stratocumuls clouds often appear in rows or patches.

You can distinguish stratocumuls from stratus by looking for more variations in color and a lumpier appearance

77
Q

Stratocumulus clouds

A

Low-lying clouds with both layered and convective aspects.

Stratocumulus are distinguished from stratus clouds by variations in color across the sky

78
Q

Cumulus (cu) clouds

A

Have well-defined, flat bases and are intricately contoured domed tops resembling cauliflower

The edges of the cloud are distinct

bases - dark gray and sunlit sides are bright white

79
Q

Two basic forms of cumlus clouds

A

Fair-weather cumulus

Cumulus congestus

80
Q

Fair-weather cumulus clouds

A

Symbolize pleasant weather conditions all over the world

Height similar to width

These clouds are common in summer when solar heating of the surface triggers convetion

Not deep enough to cause rain, grow into large storms

81
Q

Cumulus congestus - towering cumulus

A

Tall relative to their width

For these clouds to form, the atmosphere must have a deep unstable layer, deeper than is required for the formation of the fair-weather cumulus

These towering clouds are common in summer and may have light rain falling from them

When cumlus gongestus form in the morning, it is a good indicator that storms may form later in the day

82
Q

Nimbostratus

A

Deep clouds that bring precipitation and appear dark gray to pale blue in color

The cloud base is difficult to see because precipitation is falling from the cloud

Look similar to stratus, stratocumlus, or altostratus clouds

Nimbostratus clouds often precede warm fronts

Precipitation is often continuous and light to moderate in intensity

83
Q

Cumulonimbus

A

Thunderstorm clouds

They extend upward to high altitudes, often to the tropapause and sometimes in the lower stratosphere

Produce large amounts of precipitation, severe weather, and even tornadoes

84
Q

A distinguishing feature of cumulonimbus is the flattened )______________ shape of the top of the cloud

A

anvil

*anvil develops when the updraft slows and spreads outward hoizontally as it encounters the very stable air in the stratosphere

85
Q

Underneath the anvil, sinking air may create pouches called ______________

A

mammatus - these clouds are not severe weather, they can form under the anvils of strong thunderstorms

86
Q

Where do cumulonimbus clouds develop?

A

Develop in unstable, moist atmospheres and are fairly common in the United States in spring and summer

They often occur ahead of cold fronts.

In summer they can form over mountains because orographic lifting in combination with solar heating

can be isolated or in groups

87
Q

Altostratus (As)

A

Layered clouds made up mostly of liquid water droplets

Gray to pale blue in appearence

Form when middle layers of the atmosphere are moist and slowly lifted

Observe ahead of a warm front, before the nimbostratus

88
Q

Altostratus and Altocumulus are ___________ clouds

A

middle

89
Q

Altocumuls (Ac) clouds

A

They can be thin or thick, white or gray, and organized in lines or randomly distributed

occur in middle levels of the atmosphere

Similar in appearance to stratocumlus, with a higher cloud base

90
Q

Cirrocumulus`

A

Clouds are thin, white clouds that appear in ripples arranged in a regular formation.

Composed of ice crystals and occur high in the atmosphere in regions that are moist and unstable

“mackeral sky”

91
Q

Cirrostratus

A

Can cover part or all of the sky

Uniform in appearance and can be thin or thick and white or light gray in color

Common during winter

92
Q

Cirrus (Ci)

A

wispy, fibrous clouds that are made of ice crystals

They often occur as wisps here and there across the sky and are aligned in the same direction as the upper-level winds

93
Q

Water vapor is an important greenhouse gas because _________________

A

it absorbs longwave energy effectively

94
Q

Increases in greenhouse gases over time can result in a climate change because:

A

the atmosphere becomes more effective at absorbing longwave energy emitted by the surface

95
Q

Evaporation depends on _____________

A

relative humidity

96
Q

With a lower relative humidity, more __________ occurs

A

evaporation

97
Q

Clouds also have a warming effect on atmosphere below them because they are very good emitters and absorbers of ________________

A

terrestrial radiation

98
Q

Clouds reflect _____________

A

solar radiation

99
Q

The size and shape of a crystal is called its ____________

A

crystal habit

100
Q

_______________ determines the particular crystal habit of ice

A

Temperature

101
Q

Hexagonal plate

A

0 to -5 degrees C

  • 10 to -12 degrees C
  • 16 to -25 degrees C
102
Q

Needle

A

-5 to -10 degrees C

103
Q

Dendrite

A

-12 to -16 degrees C

104
Q

Column

A
  • 5 degrees to -10 degrees C
  • 25 to -50 degrees C
105
Q

The dendrites are hexagonal with _____________

A

elongated branches, or fingers, of ice

They most closely resemble what we think of as snowflakes

106
Q

Precipitation

A

Any liquid or solid water particles that falls from the atmosphere and reaches the ground

Can be long lasting and steady, or it may fall as a brief and intense shower

107
Q

Precipitation removes_____________ from the atmosphere

A

water vapor

108
Q

______________ are not precipitaiton because they do not fall from a cloud under the force of gravity

A

Dew and frost

109
Q

_______________ are those that have temperature greater than freezing throughout the cloud

A

Warm clouds

110
Q

____________ have temperatures that are below freezing

A

Cold clouds

111
Q

Collision-coalescence

A

A process that could produce a larger drop quickly would be to combine many smaller particles

To do this the cloud particles have to bump into each other and merge together, or coalesce

112
Q

Most clouds outside the tropical regions have temperatures that are ___________

A

below freezing

113
Q

Accretion

A

The process of ice crystal growth by sweeping up supercooled water drops

114
Q

Graupel

A

An ice particle produced by the accretion process that has a size between 1 and 5 millimeters and no discernible crystal habit

115
Q

Aggregation

A

The process by which ice crystals collide and form a single larger ice particle

Probability that two crystals will stick together depends on the shape of the crystals.

Dendrites will stick together, plates probably wont

116
Q

Snowflake

A

An individual ice crystal or an aggregate of ice crystals

Snowfalls do not consist of single crystals

117
Q

Bergeron-Wegener process

A

Ice crystal growth process

118
Q
A

Weather and Climate (10 decks)

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