Meteorology 1010
Vocabulary – Final List
Note to students: The definitions below are more or less informal, based on class discussion. More
formal or official definitions are found in the textbook. This less technical vocabulary is more likely to
appear in exams than more technical definitions. To help you along, I have provided some definitions
for you. Others you should create yourself by comparing class discussion with the textbook and other
sources. Add or change whatever detail works best for you.
----------------------------------------------------------------------------------------------------------------------------------------Absolute humidity – the actual volume or weight of water vapor in the air. The water that would drip
out of a sponge that was squeezed perfectly well to remove all water. See Relative Humidity.
Acid Precipition – natural processes create acidic and alkaline conditions based on the chemistry of
elements and compounds. Human air pollution, mostly through kicking-up dust and burning fossil fuels,
creates oxides of carbon, nitrogen and sulfur that tend to be acidic or low on the pH scale. Substances
that are very acidic or very alkaline tend to be corrosive. Corrosion dissolves or degrades other
materials or substances.
So, rain and snow can carry acidic or alkaline conditions down to soil and water. Most often, ‘acid rain’
is the issue, not alkalinity, because of acidic compounds created by burning fossil fuels. Combustion
(burning) results in molecules that consist of oxides with carbon, sulfur and nitrogen that are inherently
acidic.
Adiabatic – the change in measured temperature when air is either compressed or decompressed.
Energy is either concentrated or de-concentrated by changing air pressure, with resulting change in
temperature that does not result in gain or loss of energy. Compare adiabatic to ‘lapse rate’.
Advection – mostly horizontal movement of air that may produce fog as moist air cools to condensation
so that invisible vapor becomes visible liquid water.
Albedo – the reflectivity of a surface. High albedo surfaces absorb little energy. Shiny and/or white
surfaces such as ice and snow tend to exhibit high albedo, with greater than 90% of energy being
reflected rather than absorbed. Liquid water tends to have an albedo of less than 10%.
Alto – mid-level clouds are labeled Alto, and are generally located in between high cirrus clouds and low
stratus clouds. When alto clouds are associated with accumulation of cloudiness in rising air they can be
labeled altocumulus. When mid-level alto clouds cover a large portion of the sky we may call them
altostratus. See also Cirrus and Stratus.
Anthropogenic – ‘anthro’ refers to human and ‘genic’ means genesis or source. So, anthropogenic
means ‘human caused’.
AQI – Air Quality Index – a standard, generalized way of reporting air quality and hazards based on five
major pollutants: ozone, particulate matter, and oxides of nitrogen, carbon and sulfur. Ozone is the
single most common reason for air-quality alerts and warnings in the Salt Lake area, mostly because
oxides can combine with sunshine and heat to produce hazardous levels of ground-level ozone. AQI
levels above 100 are considered bad for health. A few places can reach many times higher at times.
Circumference – the distance all the way around a sphere or circle at its widest location. Compare to
diameter.
CFC – chloro-fluoro-carbons. Synthetic molecules that form the basis for thousands of useful products.
CFC molecules sometimes escape into the atmosphere where they destroy atmospheric ozone. CFC
production has been banned for many years, and many more years will be needed before the earth’s
“ozone layer” will recover because CFC molecules persist for decades, and each CFC molecule can
destroy thousands of ozone molecules.
Chinook wind – see also Katabatic wind
Cirrus – the highest clouds in the atmosphere. Cirrus clouds are mostly high-altitude ice crystals. Cirrocumulus clouds show small puffiness that is characteristic of rising air. Cirro-stratus clouds are visible ice
particles that cover enough of the sky to be called ‘layer’ or ‘stratus’.
Climate zones (A-E and H) Climograph – provides two major categories of weather and climate information: annual temperature
range and rainfall, by monthly totals, with averages and extremes.
Clouds – when vapor condenses back to liquid and becomes visible. Clouds are liquid water suspended
in the air. Major types include: stratus (layered) alto (mid-level), cirrus (higher altitude) and cumulus.
High-altitude clouds are ice particles. Some cumulus clouds are classed “vertical development” because
humidity and heat produce unstable conditions, wherein rising air condenses out moisture and heat,
provoking further rising air. Clouds of vertical development can produce violent weather as rapidly
rising air provokes high-speed surface winds and strong turbulence aloft, and likelihood of lightning, hail
and possibly tornadoes.
Cloud Seeding – adding condensation nuclei to the air provides objects that can absorb liquid water that
has condensed from vapor. You could say that condensation nuclei is “dirt that gives water something
on which to stick”. Without such ‘sticking’ surfaces, rainfall and snowfall would be almost impossible.
Condensation – compare to evaporation and latent heat. Condensation is the release of invisible water
vapor and latent heat back to liquid water and sensible heat (heat you can feel and measure as
temperature). So, evaporation is the process of ‘hiding’ heat when energy is used to evaporate liquid
into vapor, and condensation is the reverse process where vapor returns to liquid.
So, if evaporation is a cooling process, then condensation is a warming process. That is why cumulonimbus clouds may continue to rise: latent heat is released when clouds form.
Conduction – transfer of sensible heat (as temperature) between substances by direct contact or touch.
Transfer of energy does not include the objects themselves moving, but only that energy is transmitted
through the objects.
Continental climate – land areas heat up and cool down much more quickly and often than do water
bodies. So, climate and weather are much more severe or extreme over large continental land masses.
Convection – transfer of sensible heat or energy by flow or movement of fluids (air or liquid) across
space. Energy transfer is by movement of the substance that is holding the energy.
Convergence – where masses of air are moving toward each other. The ITCZ represents masses of air
moving toward the Equator from either side before lifting.
Cooling Degree Day (CDD) – the difference between a daily average temperature and a base
temperature of 65 degrees F. CDD represents the amount of building cooling needed in order to reach a
standard indoor daily temperature average of 65 degrees F. Each degree of daily average temperature
above 65 degrees F amounts to one cooling degree day (CDD). The cooling load needed for a building
across an entire year is found by adding up all of the daily average temperatures that are above 65
degrees F. See Degree Days and Heating Degree Days.
Corona – means ‘crown’ or a shiny circle around the sun or moon, caused by sunlight passing through
ice or water vapor. As with most optical phenomena we see in the atmosphere, water in the air causes
light rays to change direction and/or be divided into different colors based on how differing wavelengths
are treated by water in the air.
Cumulonimbus – known as “clouds of vertical development” these clouds are created by vigorously
rising air that can lift through all the other cloud types. These clouds are associated with thunderstorms
and other potentially violent weather. Cloud tops can reach into the realm of the jet stream and the
stratosphere when enough heat and water vapor are available for vigorous, sustained lifting of air.
Cumulus – clouds that are building or accumulating. Cumulus clouds represent rising air that is humid.
When cooling occurs with altitude decompression, vapor converts back to liquid water that is visible as
fog in the sky. Cumulus clouds are often part of bumpy, turbulent weather as air rises and condenses
moisture in one place while air nearby is clear because it is more stable or even descending.
Degree Days – The difference between outside air temperature and the ideal or standard indoor
temperature of 65°F. Each daily average deviation from that standard adds to either the need for indoor
heating (furnace) or indoor cooling (air conditioning). The total deviation per day is called either
“Heating Degree Days” or “Cooling Degree Days” CDD. Severe climates exhibit high heating degree
days (HDD) and/or high cooling degree days (CDD).
Dew point – the temperature at which vapor in the air cannot continue to be held as vapor, but returns
to liquid state. Morning dew on the grass represents a situation where air has cooled to the point
where water cannot be held as vapor, but returns to liquid state by sticking to grass. In a sense, the
grass serves as condensation nuclei – something “to stick to” when there is no longer enough energy for
water to be in vapor state.
In the atmosphere, air may cool to the point where vapor condenses back to liquid and a cloud forms.
Clouds are not vapor, but liquid water droplets that form on aerosols or ice particles in the atmosphere.
Diameter – the distance across the center of a sphere or circle, usually at the widest place.
Diffraction – when sunlight is broken into rainbow colors as light passes close to water droplets.
Refraction also causes sunlight to break into component colors.
Diffusion – when light is scattered by collision with dust, water vapor or other objects along its path.
Diffuse light is softer and less distinct. Diffusion also accounts for why light can go under a tree or other
solid object: light has been scattered in different directions rather than simply traveling in a perfectly
straight lines that would leave sharp, perfect shadows.
Dispersion – separation of colors by reflection
Divergence – a high-pressure air flow where parcels or air are moving away from each other. Compare
to convergence.
El Niño – A seasonal reversal or slow-down of the west-moving trade winds. The result is that warmer
water does not concentrate in the far western Pacific (for storms), but remains more in the eastern or
American side of the Pacific Ocean, resulting in more precipitation in areas that tend to be dry. See La
Niña.
(Students: Take time to study the “El Niño phenomenon that starts on page 210 in the textbook. More
discussion later.)
Equinox – when world-wide days and nights are the same length, 12 hours each. Vernal (Spring)
equinox is on or about March 20 and Autumnal (Fall) equinox is on or about September 20.
Extrapolate – The process of projecting a line of data into the future. Using data from Monday to
Wednesday I can project ahead to estimate Thursday and Friday. Compare to Interpolate.
Fog – clouds of visible, liquid water suspended in air: orographic (upslope or mountain), advection,
radiation and steam fog.
Frontal or wedge – storms. Convective storms that are especially vigorous or violent because the nearby
presence of cooler, drier air induces more vigorous updrafts of warmer, more humid air. Violent
thunderstorms, including hail, lightning and damaging winds are associated with “frontal” weather
where cooler air “wedges” underneath more buoyant air.
Geostationary – a satellite that is moving around the Earth at the same speed as the Earth is turning.
When both are moving together, they are geo-stationary. A geostationary satellite is basically “parked”
at a certain location above the Earth, so it can observe events below continuously, rather than only each
time the orbit passes over that place. By contrast, polar orbit satellites travel north--south, allowing a
satellite to observe the entire Earth over time. The east to west rotation of the Earth, combined with
north-south polar orbit will eventually cover the entire Earth.
GPS – a set of orbiting satellites that transmits regular signals that can be used to determine position.
By comparing angles and distances to and from satellites we can determine the location of any object
and the speed of its movement. GPS is very important for gathering and process weather information.
Greenhouse gas – some atmospheric gases act as a lid or cover on the atmospheric, just as window glass
on cars and buildings helps keep things in or out. Most solar energy enters the atmosphere easily
because of its mostly small wave lengths. In contrast, after being absorbed by the Earth, solar energy
mostly converts to relatively longer-wave radiation that escapes the Earth and its atmosphere less
easily.
Greenhouse gases tend to absorb longer wave radiation. Infrared energy is relatively longer wave
radiation that we can often feel heat. Infrared (IR) is easily absorbed by carbon dioxide and other
“greenhouse” gases. So, greenhouse gases are better at allowing solar energy in, and better at
absorbing longer wave radiation that is trying to escape. So, greenhouse gases will tend to make the
Earth warmer, just as a glass window will allow solar energy in, and then tend to help keep it in.
That is why a parked car will tend to warm up in the sun: short wave solar energy easily passes through
the glass, and has more difficulty getting back out once it has been absorbed and converted to longwave radiation. For a parked car to cool down may take most of the night, because longer-wave
radiation has more difficulty radiating back to space than does shorter wave radiation coming.
Hadley Cell – World-wide air circulation based on rising air in the tropics moving north and south and
then subsiding. Similar north-south cells of rising and falling air exist in latitude bands further north and
south.
Hail – even on a hot day, a thunderstorm high in the troposphere typically includes ice crystals that
serve as condensation nuclei. Such nuclei help coax precipitation to occur by providing a surface on
which vapor can convert back to liquid. In other words, dirty surfaces that can hold or absorb water
help precipitation to occur. A hailstone begins with vapor condensing to liquid by attaching to a bit of
dirt or ice.
A hailstone represents ice that is blown back up into icy clouds to receive additional coatings of ice until
the ‘stone’ is heavy enough to fall to earth. Hailstones often contain many layers, after being blown
back into the sky many times by updrafts that occur in low-pressure, rising air events like
thunderstorms, tornadoes and hurricanes.
Halo also sun dog, pillar – sunlight modified by passing through different shapes of ice
Heating Degree Day (HDD)– the difference in daily average outdoor temperature below a standard base
of 65 degrees F. If a daily average temperature reaches 64 degrees F, then the heating requirement to
maintain the base of 65 degrees would be one degree. The total annual HDD, or heating load required
to maintain 65 degrees F, is the total annual number of degrees by which average daily outdoor air
temperature is lower than 65 degrees F. See Cooling Degree Day (CDD).
Humidity - relative versus absolute.
Hurricane –
Hydrocarbons – organic compounds composed mainly of hydrogen and oxygen bonds. Most fuels,
foods, and living things are hydrocarbons. Hydrocarbons store vast amounts of solar energy in the form
of organic compounds that are living, or once were alive.
Interpolate – Trying to estimate missing data by comparing known data on either side. I can use data
from Monday and Wednesday to try to determine what happened on Tuesday. Compare to
Extrapolation.
Intertropical Convergence Zone (ITCZ) – where converging tropical air masses meet, generally near the
equator, but tending to follow the sun’s center of illumination north and south with the seasons. The
ITCZ is associated with rainy, warm weather. The ITCZ is the equatorial edge of Hadley cells where air
masses are buoyant due to being warm and humid. The far edges of Hadley cells typically display the
return flow of air, descending drier, cooler air that warms by adiabatic compression as it nears the
surface of the earth. Desert or dry conditions prevail at roughly 30°N and 30°S of the ITCZ. Utah and
Arizona are not far from the dry end of Hadley cell activity, with the opposite end being rainy and
tropical wherever the ITCZ is located.
In June, the ITCZ is mostly in the northern hemisphere, bringing a “rainy season” to those areas, with the
reverse being true in December.
Inversion – normal daily air temperature rising in the morning as solar air is absorbed and becomes
thermal or heat. When that normal pattern is blocked, air becomes layered rather than mixed.
Isoline – a line connecting points of equal value. Isohyet is a line that connects locations that experience
the same amount of rainfall. Isotherms connect locations with the same temperature. Isobars connect
points that have the same air pressure. Isobar is a line of equal air pressure; isohyet is a line of equal
precipitation, etc.
Jet Streams – high-speed bands or streams of wind that flow west to east, located in the upper part of
the troposphere (mixing zone) and below the stable, stagnant stratosphere that includes the ozone
layer. Jet streams often undulate more north and south at times, helping mix masses of air that differ in
temperature and humidity. This mixing is why the jet stream pathway is sometimes called the ‘storm
track’.
Katabatic wind – see also “Chinook”
Kinetic energy – motion of substances due to absorption of sufficient energy. Molecules vibrate more
vigorously, pushing away from each other, with a tendency to create less density. Substances that are
less dense tend to rise above heavier or denser substances.
La Niña – see El Niño
Lapse rate – The general tendency for air temperature to decline with increasing altitude. On Earth,
most energy-absorbing substance are near the surface of the earth, so daily warming occurs near the
surface as well. For class discussion, humid air is presumed to be cooler by 3°F for each 1,000 feet of
higher altitude. Dry air will tend to be cooler by 5°F for each gain in altitude of 1,000 feet. Compare
lapse rate to Adiabatic.
Latent heat – thermal energy that you can’t normally detect or feel, or even measure as temperature.
Latent or ‘hidden’ heat is bound up in vapors, such as water vapor. If enough kinetic energy (heat) is
applied to cause molecules in liquid to lose cohesion bonds, gases form and that energy becomes latent,
or hidden in the vapor. That latent heat returns to being sensible or measurable by thermometer when
water vapor condenses back to liquid. With lower kinetic motion, vapor returns to liquid and latent heat
becomes sensible, or measurable by thermometer. We can see the liquid and we can feel the heat.
Macro, Meso and Micro-scale winds Meridional Flow – jet stream flow that undulates north and south as it moves from west to east.
Meridional flow tends to provide more opportunity for air masses of differing humidity and temperature
to mix and produce storms.
Microburst – a strong downdraft of air that often occurs at the conclusion of a thunderstorm. Cooling
air can descend rapidly, sometimes brought down even faster by the weight of falling rain. Evaporation
of falling rain (virga) can further accelerate downdrafts as evaporative cooling occurs. Damaging winds
can spread out at the surface.
Mirage – things we see in the sky or atmosphere that are not located where they appear to be. Light
bends as it passes through differing parts of the atmosphere, so objects are located somewhere along a
curve away from us, not along a straight line away from us. We think light is coming to us along a
straight line, but near the surface light is actually reaching us from along a curve.
So, some mirage images appear higher above the horizon than they really are, while other objects
appear to be lower than they really are, because our minds want to believe that those objects are
located in a straight line from us to them, instead of the curved arrival that is actually the case.
Monsoon – seasonal reversal of winds. When monsoon winds occur over coastlines, then on-shore
breezes will bring rain to land areas. The reverse brings wind from land to the ocean, preventing
moisture from reaching land from the ocean. The Indian sub-continent is a classic example: as the ITCZ
moves northward in June, moisture from the ocean is drawn over land areas. During winter, the ITCZ is
far southward, resulting in dryness in India as high-pressure conditions prevail. The Utah/Arizona
monsoon is based on prevailing high pressure that rotates clockwise, drawing moisture from the Gulf of
Mexico that can result in brief thunderstorms and rain as daily rising ‘thermals’ lift that moisture to
condensation level (dew point).
Nimbus – associated with rain or precipitation.
Orographic – precipitation associated with mountains. Air is compelled to rise due to an obstacle. The
result is cooling by decompression. If dew point is reached, then precipitation may occur. See also
Convective and Frontal or wedge storms.
Outlook – an outlook is a generalized or even vague expectation for what conditions will be like during a
period of time in the future. By comparison, a prediction is very precise, involving a specific event at a
certain date, time and place. A forecast is more general than a prediction, but not as loose as an
outlook. A forecast is usually expressed as percent chance or likelihood of something occurring. An
outlook is even more general, focusing on a broader period of time with more general estimates of
events or processes.
Oxides – molecules that are made of oxygen and other elements, principally carbon, nitrogen and sulfur.
Oxides result from combustion (fire) and other chemical processes. When oxygen combines with iron,
we call it rust. Oxides from burning hydrocarbons, including fossil fuels, tend to be acidic and/or
poisonous and account for most human-caused air pollution.
Ozone – a molecule containing three atoms of oxygen. Atmospheric Ozone protects the Earth by
absorbing about 95% of all in-coming ultraviolet energy from the Sun. Ground-level Ozone is mostly a
product of sunlight interacting with oxides or nitrogen and sulfur, called ‘photochemical smog’.
So, ozone is natural as well as “anthropogenic”. Ozone is both good and bad for human health, based
on where it is located. Ground-level Ozone is poisonous, noxious and irritating.
Ozone layer – known as ‘atmospheric ozone’ because it is located mostly in a layer or band located
several miles above the surface of the Earth. Atmospheric ozone differs from ground-level ozone
because it is high above the Earth and is created when ultraviolet solar energy collides with oxygen.
Oxygen as O2 is broken into O1 and O1 - - which may re-combine with O2 into O3 (ozone). The creation
and destruction of oxygen molecules continues over and over as ultraviolet energy creates and destroys
ozone. The result is that 95% of incoming ultraviolet is absorbed by the ozone layer.
Atmospheric ozone in the ‘ozone layer’ is the same molecule as ground-level ozone but is not located
near the Earth’s surface, so it is harmless to living things. In contrast, ground-level ozone is mostly
created by air pollution and is hazardous by its proximity to people, plants, animals and many other
vulnerable substances.
Our goal should be to help nature repair the atmospheric ozone layer, which also helping eliminate
ground-level ozone.
pH – acid, neutral, base (alkali)
Photochemical smog - See Primary/Secondary below.
Pi – π – a symbol that represents the constant, un-changing relationship between the diameter of a
circle and its circumference. Pi or π is about 3.1415 and never changes. So, multiplying π by the
diameter will always yield the circumference. Dividing the circumference by Pi will always yield the
diameter.
For the Earth, a diameter of about 7,923 miles will yield a circumference of about 24,900 miles, based
on C = Pi x D.
Primary/Secondary – for air pollution, a primary pollutant is a substance made directly, while a
secondary pollutant is created by a primary pollutant interacting with else in a further way. For
instance, oxides of nitrogen (NOx) and sulfur (Sox) are primary air pollutants produced directly by
industrial process, fires and motor vehicle engine combustion. These primary pollutants combine with
sunlight and atmospheric heat to form ground-level ozone, which is a secondary pollutant, and is part of
‘photo-chemical smog’.
Radiation – long wave vs short wave. Radiation is the only means by which solar energy reaches the
earth. Radiation is not heat or kinetic motion until it has been absorbed by substances. Most solar
energy is relatively short wave length, whereas most out-going radiation is in the longer wavelengths.
Radiation can also occur as a means of transferring energy between substances, in addition to incoming
and outgoing radiation. Solar radiation that is not absorbed and converted to kinetic energy (motion,
heat), is due to being reflected back into outer space.
Rainbow – sunlight can be broken into its component colors by passing through, or near water and/or
ice.
Reflection – solar rays or other electromagnetic energy that “bounces” off a reflective surface at the
same angle it arrived. Reflected energy is not absorbed, does not convert to kinetic or thermal energy
and is generally not part of the earth’s greenhouse effect.
Refraction – The pathway of light waves is re-directed at a different angle when sunlight passes through
substances such as water. Different colors of the spectrum (rainbow) bend at different angles, based on
their different wave lengths.
Relative humidity – compare to absolute humidity. Relative humidity is a ratio, or comparison between
how much actual (absolute) water is present in a parcel of air, and how much could be present in that
same parcel. Relative humidity is a ratio of actual compared to capacity. Absolute humidity is simply
the mass of vapor in the air, which relative humidity compares that vapor to the potential vapor that
might be present if saturation occurred.
Ridge – a line of higher-pressure air. Areas of higher air pressure tend to produce descending air, with
dry or mild conditions. Compare to Trough.
Sensible heat – thermal energy or heat that you can sense or feel, measured as temperature. Sensible
heat is kinetic energy, the energy of molecular movement or vibration. Compare to latent heat.
Solstice – the calendar date when the Sun is directly overhead at the highest latitude. The June solstice
finds the sun directly overhead at noon at about 23.5 degrees latitude north of the Equator. The line of
latitude where this occurs all the way around the Earth is called the Tropic of Cancer.
The December solstice finds the sun’s rays falling from directly overhead at 23.5 degrees of latitude
below the Equator (Tropic of Capricorn).
Storm Surge – the total rise in sea level that occurs during a storm. Storm surge consists of several
parts:
-
-
Low barometric pressure allows ocean water to rise, as compared to ocean level that is
under greater atmospheric pressure elsewhere. This rise can be as much as three feet
above normal sea level.
High wind in storms can create high waves that can be pushed in land great distances.
In fact, aside from wave crests that are whipped-up by the wind, the base level of the ocean
along the coast is pushed inland. This is a form of upstream flooding called inundation.
Heavy precipitation that is normal with severe storms can cause downstream flooding that
adds to upstream inundation.
Aside from water movement, high winds are also damaging as they lift, move or break-up
buildings and other objects.
Stratosphere – the ‘layered’ part of the atmosphere, such as the ozone layer.
Stratus – stratus clouds are layered and often cover a large portion of the sky. Stratus clouds are
generally low-level clouds, below alto and stratus. When low stratus clouds involve rain they are called
nimbostratus. When cumulus build-up is in broad layers we may call them stratocumulus. See Alto and
Cirro also.
Sub-tropic – regions north and south of the tropics are typically dry and fairly calm most of the time,
because of subsiding air that warms by compression as it falls. Sub-tropics range from 25-35 degrees
latitude.
Super Cell – see also Meso-Scale convective complex
Theory – a well-tested hypothesis that is widely useful and consistently reliable. An extremely useful
theory may someday be regarded as a ‘paradigm’. Even the best paradigms seldom meet the test of full
proof. We live and die by theories and paradigms.
“Tornado Alley” – the central plains of the United States are low, relatively flat country where cold, dry
air from the north and west can collide with warmer, wetter air from the southeast.
Trade Winds – winds blowing from the east all the way around the earth. These bands of prevailing
wind are located just north and just south of the equator and separate the tropics from the subtropics
that are the next bands of atmosphere north and south of the trade winds. Trade winds bring moisture
for storms to the southeastern United States and are associated with periodic “El Niño” conditions when
prevailing easterly winds slow, stop or even reverse for a season.
Tropic:
-
Of Cancer
Of Capricorn
Equatorial climate
Troposphere – the lower atmosphere where mixing and turbulence occur. Gases are mixed and much
water vapor and aerosols are present. Compare to the stratosphere where atmospheric gases are
layered and general stagnant.
Trough – a line of lower-pressure air. A trough of low-pressure indicates rising air. Lower or falling air
pressure tends to produce clouds and storminess. Compare to Ridge.
Ultraviolet – Uv – solar energy in the mid-size wave length band. Ultraviolet is close to the visible light
band. Both deliver large amounts of energy that converts to heat upon absorption.
Urban “heat island” effect – large cities tend to include vast amounts of dark, hard surfaces rather than
natural cover, such as earth, water and green vegetation. The result is summer concentration of
excessive daily heat over large urban areas, with concentration of air pollution resulting from rising air
that draws pollution toward the center.
Vapor – a state of being evaporated, or vaporized. Adding enough energy to a substance to result in
going from solid or liquid state to a vapor state, the most energetic state of atoms and molecules.
Virga – rainfall that evaporates before it reaches the ground. Evaporative cooling by virga can lead to
rapid downdrafts of air, or even a damaging “micro burst”.
Zonal Flow – westerly jet stream flow that tends to be straight-line from west to east, rather than
undulating north or south along its path to the east. See Meridional flow.