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Questions from the Textbook Meterorology Today, 9th edition by C. Donald Ahrens

The temperature at which saturation occurs

dew point

Condensed water vapor that forms on surfaces such as twigs, leaves, and blades of grass as the temperature drops.


The dew becomes ____ dew when the air temperature drops below freezing.

frozen dew

Averaged for an entire year in middle latitudes, dew yields a blanket of water between ____ thick.

12-50mm thick

On clear, calm nights, objects near the earth's surface cool rapidly by emitting _____ _____

infrared radiation

Dew is more likely to form on nights that are ____ and _____ than on nights that are _____ and _____.

clear and calm, cloudy and windy

Cloudy, windy weather that inhibits rapid cooling near the ground and the forming of _____ often signifies the approach of a _____ storm system.

dew, rain-producing

The name for dew-point when the temperature drops below freezing.


When water vapor changes directly into ice.


When air cools to the dew point, the relative humidity becomes _____% and the air is saturated. Continued cooling condenses some of the vapor into tiny ____ _____

100, cloud droplets

A volume of air about the size of an index finger contains between _____ and ____ particles.

1000 and 150,000

Particles which serve as surfaces on which water vapor can condense.

condensation nuclei

British physicist who discovered that water vapor condenses on nuclei.

John Aitken

Particles ranging from 0.2 to 1um

large nuclei

Particles with a range exceeding 1um

giant nuclei

Condensation nuclei most favorable for producing clouds have a radii of ____um

0.1 and are called cloud condensation nuclei

Provide the the major source of cloud condensation nuclei in the marine atmosphere.


Means "water-seeking". eg: salt


Means "water-repelling". eg: oils, gasoline, waxes


Haze, fog, and clouds will form at relative humidity near or below ____% due to the mixture of particles in the air.


A layer of dust or salt particles suspended above a region.


As humidity increases from about 60% to 80%, the scattering effect of wet haze increases a factor of nearly ____.


The thin white veil across the horizon is due to ____


When the visibility lowers to less than 1km, and the air is wet with countless millions of tiny floating water droplets, the wet haze becomes a cloud resting near the ground, which we call _____


Fog that forms over cities is _____ than fog that forms over the oceans with eh same water content due to the greater number of nuclei.


Fog that forms in polluted air can turn acidic as the tiny liquid droplets combine with gaseous impurities, such as oxides of sulfur and nitrogen to form _____

Acid fog

Two ways in which fog forms:

1. by cooling- air is cooled below its saturation point (dew point)
2. by evaporation and mixing- water vapor is added to the air by evaporation, and the moist air mixes with relatively dry air

_____ and _____ are the primary means for cooling the nighttime air near the ground.

radiation and conduction

Fog produced by the earth's radiational cooling is called ______ fog

radiation fog (ground fog)

Occurs when warm, moist air moves over a cold surface and the air cools to below its dew point

Advection fog

Fog that forms as relatively wars moist air moves over a colder surface that cooled mainly by radiational cooling.

Advection-radiation fog

Fog that forms as moist air flows up along an elevated plain, hill or mountain.

upslope fog

Fog produced when sufficient water vapor is added to the air by evaporation, and the moist air mixes with relatively drier air.
The two common types are _____ fog, which forms when cold air moves over warm water, and ______ fog, which forms as warm raindrops evaporate in a cool air mass.

Evaporation (mixing fog)
steam, frontal

A cloud resting on the ground composed of water droplets, ice crystals, or a combination of both.


A visible aggregate of tiny water droplets or ice crystals suspended in the air.

a cloud

There are ___ basic types of clouds.


Latin to English:

layer - sheet like
heap - puffy
curl of hair - wispy
violent rain - rain cloud

high cirriform clouds are composed almost entirely of ____ ____

ice crystals

Most common high clouds which are thin, wispy clouds blown by high winds into long streamers called mares' tails.

cirrus (Ci)

Thin, sheetlike, high clouds that often cover the entire sky. So thin that the sun and moon can be clearly seen through them. The ice crystals in these clouds end the light passing through them and will often produce a halo.

Cirrostratus (Cs)

Clouds seen less frequently than cirrus, appear as small, rounded, white puffs that may occur individually or in long rows
Usually cover small portion of the sky, small ripples resemble fish scales, mackeral sky

Cirrocumulus (Cc)

Gray or blue-gray cloud composed of ice crystals and water droplets. Often cover the entire sky across an area that extends over many hundreds of square kilometers.

Altostratus (As)

Middle clouds composed mostly of water droplets and are rarely more than 1km thick. They appear as gray, puffy masses, sometimes rolled out in parallel waves or bands. Usually one part is darker than another.

Altocumulus (Ac)

A dark gray, "wet"-looking cloudy layer associated with more or less continuously falling rain or snow.

nimbostratus (Ns)

Low lumpy clouds that appear in rows, in patches, or as rounded masses with blue sky visible between the individual cloud elements.

stratocumulus (Sc)

Puffy cloud that takes on a variety of shapes, but most often it looks like a piece of floating cotton with sharp outlines and a flat base.

cumulus (Cu)

If a cumulus congestus continues to grow vertically, it develops into a giant _____

cumulonimbus (Cb)

A uniform grayish cloud that often covers the entire sky. Resembles a fog that does not reach the ground.

Stratus (St)

Moist air crossing a mountain barrier often forms into waves. The clouds that form in the wave rest usually have a lends shape and are therefore, called ____ _____

lenticular clouds

When a cloud forms over and extends downwind of an isolated mountain peak.

banner cloud

Cap cloud. Resembles a silken scarf capping the top of a sprouting cumulus cloud.


Form in sinking air. Appear as baglike sacs that hang beneath the clouds and resemble a cow's udder.

Mammatus clouds

Jet aircraft flying at high altitudes often produce a cirrus-like trail of condensed water vapor called a condensation trail or a ____


Seen above the troposphere. Soft pearly looking clouds.

nacreous clouds

Wavy bluish-white clouds, so thin that stars shine brightly through them, may sometimes been seen in the upper mesosphere, at altitudes above _____km

noctilucent clouds

Fog formed as moist, stable air flows upward over a topographic barrier

upslope fog

The amount of time the air temperature during the winter must remain below a certain value so that fruit and nut trees will grow properly during the spring and summer.

winter chilling

Also called could condensation nuclei. Tiny particles upon whose surfaces condensation of water vapor begins in the atmosphere. Small nuclei less than 0.2um in radius are called Atiken nuclei; those with a radii between 0.2 and 1 um are large nuclei, while giant nuclei have a nuclei larger than 1um.

Condensation nuclei

Evaporation (mixing) fog- fog produced when sufficient water vapor is added to the air by evaporation, and the moist air mixes with relatively drier air. The two common types are steam fog, which forms when cold air moves over warm water, and frontal fog, which forms as warm raindrops evaporate in a cool air mass.

Steam fog

Occurs when warm, moist air moves over a cold surface and the air cools to below its dew point

Advection fog

(also called radiation frost) refers to the white ice crystals, loosely deposited on the ground or exposed objects, that form on cold clear nights when heat losses into the open skies cause objects to become colder than the surrounding air.

Hoar frost

Fog that most commonly forms on clear nights, with light or calm winds

Radiation fog

The most abundant gases in the earth's atmosphere by volume are

carbon dioxide and nitrogen

What is a variable gas in the earth's atmosphere?

water vapor

In the atmosphere, tiny solid or liquid suspended particles of various composition are called:


What gas in the atmosphere is not considered a greenhouse gas?


The outpouring of gases from the earth's hot interior is called:


Name three units of pressure:

millibars, inHg, pascals

The temperature of the tropopause is much (colder/hotter) than the temperature at the earth's surface.


The instrument that measures temperature, pressure, and humidity at various altitudes int he atmpsphere:


The heat energy released when water vapor changes to a liquid is called:

latent heat of condensation

The change of state of ice into water vapor is known as:


The proper order from shortest to longest wavelength is:

ultraviolet, visible, infrared

If the average temperature of the sun increase, the wavelength of peak solar emission would:

shift to a shorter wavelength

An important reason for the large daily temperature range over deserts is:

there is little water vapor in the air to absorb and re-radiate infrared radiation

During an equinox:

days and nights are of equal length, sun is overhead the equator, earth is not tilted toward nor away from the sun

The maximum in daytime surface temperature typically occurs ____ the earth receives its most intense solar radiation.


Seasons are caused by:

the angle at which sunlight reaches the earth, the length of the daylight hours

Lines connecting points of equal temperature


Water changes form liquid to a vapor


This is used as an index for fuel consumption:

heating degree-days

composed of ice crystals, white and whispy, indicate fair weather


ususally cover small portion of the sky, small ripples resemble fish scales, mackeral sky,


thin sheet like clouds that cover the whole sky and form a halo around the sun


composed of water droplets; only one km thick; gray puffy masses; often in parallel bands;


gray or blue ice crystals that have watery sun

alto stratus

dark gray wet looking and continuously falling rain or snow, light or moderately steady precip

nimbo stratus

low lumpy clouds that appear in rows, patches, or rounded masses


uniform grayish clouds covers whole sky kind of like fog that doesnt touch ground


puffy cottonball like clouds


aka thunderheads, bring hail and lightning and thunder


fog that forms as moist air flows upward along an elevated surface

upslope fog

artic sea smoke and steam devils are a form of this type of fog

steam fog

a tiny liquid drop of dew that freezes when the air temp. drops below freezing

frozen dew

fog that most often forms as warm rain falls into a cold layer of surface air

frontal fog

the most common type of fog along the pacific coast of north america

advection fog

light shower of snow that falls intermittently from cumuliform clouds for a short duration


ragged looking clouds that drift rapidly with the wind often beneath a nimbrosrtatus cloud


least likely to produce precipitation that reaches the ground


evaporating precip that does not reach ground


lens shaped; formed my moist air; crossing mountains

lenticular clouds

cap cloud, form above a cumulonimbus cloud or cumulus congestus cloud b/c most winds are defected to top of cloud

pileus clouds

called cow udders, form on underside of cumulonimbus clouds or form in sinking air


formed when warm air rides up and over cold surface this is why we get foggy days after a big snow followed by warm temps

frontal fog

warm moist air moves inland from gulf air passes over cooler areas and air cools below dew point and spreads over a large region and common in central US

advection/radiation fog

polluted air with condensation nuclei and is a health danger

acid fog

The percent of water vapor in the air compared to that required for saturation.

relative humidity

The lowest temperature that can be attained by evaporating water into the air is the ____ ____

wet bulb

The temperature at which the air must be cooled for saturation to occur is called the ____ ____

dew point

On most days the relative humidity reaches its highest value when the air temperatures reaches its ____ value.


The circulation of water within the atmosphere is called the ____ cycle.


Instruments that measure humidity are called ____


When the air temperature increase, the saturation vapor pressure:


Which is the best indicator of the actual amount of water vapor in the air?

dew-point temperature

If the air temperature remain constant, evaporating water into the air will ____ the dew-point temperature and ____ the relative humidity.

increase, increase

Why in NA the Gulf Coast states are more humid in summer than the coastal areas of southern California?

the surface water temperature of the Gulf of Mexico is very warm

What two factors cause the relative humidity of air to change.

Change air's water vapor content. Change air temperature.

Dew, frost, and frozen dew form when objects on the surface cool below the air's ____ ____ temperature

dew point

____ ____ are important int he atmosphere because they serve as surfaces on which water vapor condenses.

Condensation nuclei

Fog can form as the air____, or as water evaporates and mixes with ____ air

cools, drier

____ not only photograph clouds, they provide scientists with a great deal of physical information about the earth and its atmosphere.


Another name for visible white frost.


These particles serve as surfaces on which water vapor may condense.

condensation nuclei

Fog that forms as moist air flows upward along an elevated surface.

upslope fog

Arctic sea smoke and "steam devils" are a form of this type of fog.

Steam fog

Fog that forms when cold air moves over something a hot tub in the winter.

Steam fog

A tiny liquid drop of dew that forms as rain falls into a cold layer of surface air.

frozen dew

A positive benefit of fog for fruit and nut trees

winter chilling

Fog that most often forms as warm rain falls into a cold layer of surface air

frontal fog

The most common type of fog along the Pacific coast of North America.

Advection fog

Beads of water that have condensed onto objects near the ground


Fog that most commonly forms on clear nights, with light or calm winds.

radiation fog

A "mackerel sky" describes this cloud


A low, lumpy cloud layer that appears in rows, patches, or rounded masses.


A towering cloud that has not fully developed into a thunderstorm

cumulus congestus

Hail is usually associated with this cloud type


The sun or moon are dimly visible or appear watery through this gray, sheetlike cloud


A halo around the sun or moon often identifies the presence of this cloud


Wispy, high clouds


Light or moderate but steady precipitation that covers a broad area is most often associated with this cloud


This cloud's elements (puffs) should be about the size of your thumbnail when your hand is extended to arm's length


Lightening and thunder are associated wit this cloud


A cloud o vertical development that resembles a small piece of floating cotton


A middle cloud that occasionally forms in parallel waves or bands


The cloud with the smallest elements or puffs as viewed from the surface


A low, uniform, grayish cloud, whose precipitation is most commonly drizzle.


This clouds elements (puffs) should be about the size of your fist when your hand is extended to arm's length


When fog lifts above the surface it forms this gray, sheetlike cloud


Cloud with the greatest vertical growth


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