Meteorology Chapters 6-8

In the fog clearing technique known as _____________ (highly utilized in airports in France), a series of jet engines installed below the ground along the edge of the runway pump hot exhaust gases into air to warm and stir it, causing fog droplets to evaporate

turboclair

scintillation

twinkling or flickering of a star that occurs as starlight enters the atmosphere and often passes through regions of differing air density, each of which bend and deflect the tiny wave of starlight

When the relative humidity reaches 75%, condensation may begin on the most active hydroscopic nuclei, producing a ______ _________. Appears dull gray or white and restricts visibility

wet haze

The coolest temperature that can be obtained by evaporating water into the air is the ______________ _________________.

wet-bulb temperature

glory

A diffraction phenomenon that produces a set of colored rings that may appear around the shadow of an aircraft flying above a cloud layer composed of water droplets less than 50 micrometers in diameter

Heiligenschein

A faint white ring surrounding the shadow of an observer's head on a dew-covered lawn. Light in this manner is said to be retroreflected

crepuscular rays

Rays of sunlight that appear to radiate from a single point in the sky. These are columns of sunlit air separated by darker cloud-shadowed regions.

astronomical twilight

Sun between 12 and 18 degrees below the horizon. The sky is completely dark and the astronomical observation of the faintest stars is possible

reflection

Sunlight bounces off a surface at the same angle at which it strikes the surface

rainbow

an arc of colored light in the sky caused by refraction of the sun's rays by rain. Occur when rain is falling in one part of the sky and sun is shining in another.

scattering

an interaction of light with matter that causes light to change its energy, direction of motion, or both

Over the ocean in polar regions, steam fog is referred to as __________ _____ _________

arctic sea smoke

The scattering effect of _______ _________ produces a bluish color when viewed against a dark background and a yellowish tint when viewed against a light colored background

dry haze

Where is relative humidity highest?

north pole, south pole, equator

When light waves constructively interfere, we see ________________, where destructive interference occurs, we see ________________

bright light, darkness

How do we perceive light?

-electromagnetic waves stimulate antenna like nerve endings in retina of human eye

If fog is thick with little sunlight penetrating it, and there is little mixing on the outside edges, the fog may not dissapate. Since the fog does not touch the ground, and a strong inversion exists above it, the fog is called a _______ ______________ _______. (The low cloud above the ground is also called __________ or simply ______ ____)

-high inversion fog -stratus, high fog

Air with a 50 percent humidity actually holds how much of the water it could hold? 100% relative humidity?

-one half its full capacity -filled to capacity (saturated)

For the optical phenomena of brocken bow, glory, iridescence, and corona to occur, how do you have to be oriented to the sun? How must the light behave?

-to your back -light clings slightly to the edge of the droplet and skims along the surface of the droplet as a surface wave for a short distance

secondary bow

Much fainter; seen above the primary bow colors are in reversed order of primary

brocken bow

A bright ring of light seen around the shadow of an observer's head as the observer peers into a cloud or fog bank. Formed by diffraction of light.

superior mirage

A mirage in which the image appears above the true position of the object., often when air near ground is much cooler than air above

blue haze

A result of a particular process in which hydrocarbons called terpenes are released by vegetation to combine chemically with ozone, which filters down from the stratosphere. This produces small particles that selectively scatter blue light

Some condensation nuclei are quite small and have a radius less than 0.2 micrometers, these are referred to as ___________ _________

Aitken nuclei

tangent arc

An arc of light tangent to a halo. It forms by refraction of light through ice crystals.

mirage

An object appears to be displaced from its true position

white night

At high latitudes during the summer, morning and evening twilight may converge, producing a nightlong twilight

iridescence

Bright areas of color that occur when different size droplets exist in the cloud and it becomes distorted and irregular. Most often observed within 20 degrees of the sun

Another factor promoting the formation of radiation fog is a light breeze of less than five knots. Why does this promote radiation fog?

Brings more of moist air in direct contact with cold ground and transfer of heat occurs more rapidly

sun pillars

Caused by reflection of sunlight off light crystals. Most often appear at sunrise or sunset as a vertical shaft of light extending upward or downward from the sun. May form as hexagonal plate like ice crystals fall with their flat bases oriented horizontally

civil twilight

Lasts from sunset until sun is 6 degrees below horizon

Saturation vapor pressure

Maximum amount of water air will hold (warm air hold more water than cold air) at any temperature

Three regions stand out as having the most days with heavy fog in the US:

Pacific Coast states, Appalachian highland region, New England

critical angle

The angle at which some of the sunlight striking the backside of a raindrop is reflected within the drop

refraction

The bending of a wave as it passes at an angle from one medium to another

destructive interference

The interference that occurs when two waves combine to make a wave with a smaller amplitude

absolute humidity

The mass of water vapor contained in a certain volume of air

primary rainbow

The rainbow of visible spectral colours that results from a single internal reflection in rain drops.

The dry thermometer (commonly called the ______ __________) gives the current air temperature

dry bulb

Suppose you visit an area that contains a large concentration of suspended dust or salt particles. There you may notice that distant objects are usually more visible in the afternoon than the morning, even when the concentration of particles in the air has not changed. Why?

Warm afternoon temperatures drop the relative humidity of the air below the point where water vapor begins to condense

inferior mirages

When the air near the ground is much warmer than the air above, objects may not only appear to be lower than they actually are, but also (often) inverted

corona

When the moon is seen through a thin veil of clouds composed of tiny spherical water droplets, a bright ring of light may appear to rest

lower tangent arc

When the sun is above the horizon, it may form on the lower part of the halo beneath the sun

upper tangent arc

When the sun is on the horizon, the arc that forms at the top of the halo

constructive interference

When two crests of a wave come together to produce a much larger wave

mixing ratio

a comparison of the mass of water vapor in the parcel to the mass of dry air

Fata Morgana

a mirage that transforms a fairly uniform horizon into one of vertical walls and columns with spires

Sundogs

a phenomenon that creates the illusion of a "mock sun" or a bright ring or halo, on either side of the sun. They can be seen in any season in any place. Also called mock suns, or parhelia

______ _____ is fog that forms in polluted air that can turn acidic as tiny liquid droplets combine with gaseous impurities such as oxides of sulfur and nitrogen

acid fog

Since atmospheric pressure varies only slightly at earth's surface, the dew point is a good indicator of the air's _________ _________ __________ content

actual water vapor

Cooling surface air to its saturation point may be accomplished by warm moist air moving over a cold surface. Fog that forms in this manner is known as _____________ _____

advection fog

Advection fog also forms over land. Because the cold ground is often teh result of radiation cooling, fog that forms in this manner is sometimes called _______________-______________ ______

advection-radiation fog

When is white light perceived?

all visible wavelengths strike the cones of the eye with nearly equal intensity

Dew is more likely to form in what kind of nightly weather?

clear and calm nights

_____ _________ forms when the air temperature is below freezing and most fog droplets remain as liquid water. Liquid fog in below freezing air is also called _____________ ______.

cold fog; supercooled fog

Particles that serve as surfaces on which water vapor may condense are called

condensation nuclei

Fog, like any cloud, usually forms in one of two ways: (1) _____________ - air is cooled to its dew point (saturation point); and (2) by _______________- water vapor is added to the air by evaporation, thus raising dew point until air becomes saturated

cooling, evaporation

The amount of refraction depends primarily on two factors: the _____________ of the material and the ___________ at which light enters the material

density, angle

Absolute humidity represents the ____________ of water vapor in the parcel, and normally, is expressed as ____________ (units).

density, grams/meters cubed

When the air temperature cools to the frost point and further cooling occurs, water vapor can change directly to ice without becoming a liquid first - a process known as _________________

deposition

As the air cools slightly below the dew point, water vapor condenses on the nearest available surface, forming tiny visible specks of water called _________

dew

frost point

dew point is below freezing; temperature to which air would have to be cooled for saturation to occur

Scattered light is also called _______________ light.

diffuse

Raleigh scattering

dispersion of electromagnetic radiation by particles that have a radius less than one- tenth the wavelength of the radiation; angle of sunlight varies inversely as fourth power of wavelength so blue is scattered most and sky appears blue

The ______________ _________________ is another instrument used to measure humidity. It consists of a flat plate coated with a film of carbon that translates electrical resistance of carbon coating into relative humidity

electrical hygrometer

Fog may also form if enough water vapor is added to the air by evaporation. Fogs that form in this way are called _______________ ____.

evaporation fogs

When visibility lowers to less than 1 km, 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

In very dry weather, the air temperature may become quite cold and drop below freezing without ever reaching the frost point and no visible frost forms. These conditions can severely damage crops

freeze, black frost

A warm rain falling through a layer of cold, moist air can produce __________ ________. This normally develops in shallow layer of cold air just ahead of an approaching warm front or behind a cold front.

frontal fog

Beads of frozen water observed on objects after a clear, cold, windless night are _________ _______.

frozen dew

retroreflection

great source of contrast

The _______ _____________ uses human or horse hair to measure relative humidity, though it is not as accurate as the psychrometer.

hair hygrometer

_______ actual vapor pressure indicates large numbers of vapor molecules, while _______ actual vapor pressure indicates comparatively small numbers of vapor molecules.

high, low

The delicate white crystals that form through deposition are called __________________

hoarfrost, white frost, frost

Some particles are ___________ and resist condensation even when the relative humidity is above 100%

hydrophobic

Some particles are _________________ and water vapor condenses on these particles when the relative humidity is considerably lower than 100%

hygroscopic

In extremely cold arctic air, ice crystals form instead of water droplets, producing an ______ _______

ice fog

the ________ ________________ measures atmospheric humidity by measuring the amount of infrared energy absorbed by water vapor in a sample of air

infrared hygrometer

Particles (condensation nuclei) ranging in size from 0.2 to 1 micrometers are called ______ _________ and others, called ________ _________ are much larger and have radii exceeding one micrometer

large nuclei, giant nuclei

As a cloud grows ________ and _________, more sunlight is reflected from the cloud and hence, less light can penetrate all the way through it. Practically no sunlight penetrates a cloud whose thickness is ________ m. Since little sunlight reaches the underside of the cloud, little light is scattered and the cloud base appears _________

larger, taller, 1000, dark

Light that travels from a less dense to more dense medium ________ speed and bends toward the normal, which light that enters a less dense medium __________ speed and bends away from the normal

loses, gains

specific humidity

mass of water vapor in an air parcel is compared with the mass of all the air in the parcel (including vapor)

Specific humidity measures the _______ of water vapor in a fixed _________________________, and the mixing ratio describes the mass of water vapor in a fixed mass of the remaining dry air

mass, total mass of air

Absolute humidity tells us the _________ of water vapor in a fixed volume of air, or the _________ _________ density

mass, water vapor

The actual vapor pressure of air expresses the amount of water vapor in terms of the amount of ______________ that the water vapor molecules exert

pressure

The most common instrument used to obtain dew point and relative humidity is a _____________.

psychrometer

Primary means for cooling nighttime air near the ground?

radiation and conduction

Fog produced by the earth's radiational cooling is called ______ fog. It forms best on clear nights when a shallow layer of moist air near the ground is overlain by drier air.

radiation/ground/valley

Most commonly used way of describing atmospheric moisture?

relative humidity

Two types of light receptors in the eyes?

rods and cones

When both water and ice exist at the same temperature below freezing, the ________________ vapor pressure of the air just above the water is ____________ than that of the air over the ice

saturation, greater

Mie scattering

scattering of light caused by atmospheric particles the same size as the wavelength being scattered

General rule: the more particles, the more ______________, and the ____________ the sky becomes

scattering, whiter

On occasion, over the Great Lakes, columns of condensed vapor rise from the fog layer, forming whirling "________ _______" which appear similar to the dust devils on land

steam devils

A common form of evaporation fog is the ________ ______, which forms when cold air moves over warm water.

steam fog

To see a rainbow, how do we have to be oriented with respect to the falling rain and the sun?

sun at our backs and facing the falling rain

Jacob's ladder

synonymous with crepuscular rays

diffraction

the bending of light as it passes around objects

dispersion

the breaking up of white light by "selective" refraction

transmission

the movement of light through a substance

actual vapor pressure

the partial pressure exerted by water vapor on the atmosphere (indication of air's total vapor content)

relative humidity

the ratio of the amount of water vapor actually in the air to the maximum amount of water vapor the air can hold at that particular temperature (and pressure) (ratio of water vapor content to capacity)

dew point

the temperature to which air would have to be cooled (with no change in air pressure or moisture content) for saturation to occur

twilight

the time after sunset and immediately before sunrise when the sky remains illuminated and allows outdoor activities to continue without artificial lighting

cirriform clouds

thin wispy and composed of ice crystals rather than water droplets

Fog that forms as moist air flows up along an elevated plain, hill, or mountain is called ____________ _____. Typically, it forms during the winter and spring on eastern side of mountains

upslope fog

_____________ air has a greater capacity for water vapor than does ________ air

warm, cold

The temperature difference between the dry bulb and wet bulb is known as the ______________ __________________. A large depression indicates that a great deal of water vapor can evaporate into the air and that relative humidity is low

wet bulb depression

Fruit and nut trees that have finished growing during the summer and fall require _________ _____________- a large number of hours with the air temperature below 7 degrees C (45 degrees F) before trees will begin to grow again

winter chilling