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Christina Persch
Meteo 482
Jet Stream
Primary Points
Relatively narrow ribbon of very fast westerly winds (winds coming from the west) over the
mid-latitudes.
In a position that is at the meeting place of cold airstream from the north and warm airstreams
from the south.
Storms tend to form along this boundary below the jet stream (a front) and are steered eastward
by the jet stream above.
Large north-south temperature differences contribute to increasing vertical pressure differences
with altitude in the troposphere, which causes the wind to reach a maximum just below the
tropopause (boundary between troposphere and stratosphere).
Thousands of kilometers long, hundreds of kilometers wide, and a few kilometers thick.
Rarely forms in a straight line; instead takes the form of troughs (jet dips to the south) and ridges
(jet curves up to the north); series of curves.
Altitude: 10-13 km (6-8 miles) above the Earth’s surface.
Winds in jet stream can reach a maximum above 322 km/hr (200 mph), but tend to stay around
129 km/hr (80 mph) in the winter and around 64 km/hr (40 mph) in the summer.
Important in finding the boundaries between warm and cold air; used in predicting temperature
and precipitation; changes in weather determined by properties of air masses that upper flow
brings.
Trivia and Stories
Jet stream was first discovered during World War II.
American pilots felt the effects of the jet stream over the South Pacific.
Presence of the jet stream had only been theorized before this.
Sound Bites
Jet stream “is the shepherd that guides weather systems to their destinations”
Jet stream is “the roller coaster of the weather world”
Sources of Additional Info
National Audubon Society Field Guide to Weather by David M. Ludlum
http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/cyc/upa/jet.rxml
http://celebrating200years.noaa.gov/foundations/numerical_wx_pred/welcome.html#early
Tornadoes
Primary Points
Rapidly rotating columns of air extending from the bases of cumulus congestus or
cumulonimbus clouds to the ground.
Most dangerous tornadoes are associated with supercells and in general require the same
conditions as supercells: moist air mass below and dry air mass aloft, highly unstable
atmosphere, strong jet stream aloft, change in wind direction and speed between the lower and
upper levels of the troposphere, and some preexisting rotation in the lower layers of air.
Size and strength vary; can range from several feet to 3.2 km (2 miles) in diameter; can last from
several seconds to as long as 7 hours, and can have winds in excess of 400 km/hr (250 mph); can
move more than 320 km (200 miles).
Tornadoes occur in tornado alley so often for several reasons; mainly, this area often contains the
ingredients needed for tornado formation. Tornado alley is right between the rest of the
continental United States and the Gulf of Mexico, which means it’s the perfect breeding grounds
for a moist air mass to settle below and a dry air mass to move in aloft, since the jet stream is
known for allowing moist air to come up into this area. This contributes to creating an unstable
atmosphere, especially in April and May when north-south temperature differences are still
fluctuating from the winter months. This allows the other ingredients to come into place, creating
the perfect atmosphere for tornado formation.
Tornadoes may have a similar rotation to hurricanes, but tornadoes are less restricted in their
areas of formation. Hurricanes can really only form anywhere that’s above 10 degrees latitude
from the equator, where the Earth’s rotation is strong enough to allow for a rotating storm. They
also form over the ocean, whereas tornadoes have been known to form over land and sea (called
waterspouts in this case). Weaker tornadoes have also been known to form inside stronger
hurricanes.
Trivia and Stories
Palm Sunday Outbreak: April 11, 1965, fourth deadliest outbreak in U.S. history and the
deadliest in Indiana.
Total: 47 tornadoes killed 271 people and injured over 1,500
Indiana: 137 killed and over 1,200 injured by ten tornadoes.
Massive double-funneled tornado occurred near Dunlap, Indiana.
Sound Bites
Tornadoes are “the whirling devils of the Earth”
Tornado alley “the hot spot for destructive weather”
Sources of Additional Info
National Audubon Society Field Guide to Weather by David M. Ludlum
http://www.crh.noaa.gov/ind/?n=palmsuntor
Hurricanes
Primary Points
A rotating wind system that forms over warm tropical waters.
Usually born from a low pressure system which disturbs the tropical air over the warm ocean
waters between 10 degrees north latitude and 30 degrees north latitude. This causes instability
(i.e. thunderstorm activity).
Season begins in June and ends in November.
Size: 12-15 km (7-9 mi) high, can be up to 966 km (600 mi) in diameter.
Storm surge: ocean water pushed toward the shore by the force of the winds in the hurricane.
Combines with normal tides and can increase the water level by 30 feet or more.
Storm surge is dangerous, but the eye of the storm is probably one of the most dangerous parts
due to its deceiving nature.
People go outside and think the storm is over only to have the eyewall pass over them, which
usually contains a hurricane’s strongest winds (can reach up to 200 mph).
Prediction accuracy has improved, but the error is still fairly large, especially as the forecast goes
further out (1 day before landfall = 100 mile error, 2 days before landfall = 160 mile error, etc.)
Many factors can change the path of a hurricane at the last minute (strength and position of the
Bermuda High, for example) and the exact path can’t be predicted perfectly until it’s too late.
Intensity difficult to predict, as well; other variables can come into play and cause unforeseen
strengthening (i.e. Loop Current in the Gulf of Mexico carries warm water and can intensify a
hurricane very rapidly).
Trivia and Stories
Hurricanes were discovered by accident in the U.S.
1743: Benjamin Franklin saw that a storm had blocked out an eclipse in Philadelphia.
However, the eclipse was visible in Boston, which is about 260 miles away-concluded that
storms move.
1821: Winthrop Redfield noted that trees 70 miles apart had fallen in opposite directions due to a
major storm. Concluded that storms not only moved, but they also rotated.
Sound Bites
Hurricanes “further deceive the public with their calm, unblinking eyes”
Hurricane prediction “on a wind-whipping ride to improvement”
Sources of Additional Info
National Audubon Society Field Guide to Weather by David M. Ludlum
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://oceantoday.noaa.gov/hurricanestormsurge/
http://web.mit.edu/12.000/www/m2010/finalwebsite/background/hurricanes/hurricanesprediction.html#What_are_the_problems_with_the_current
Radar/Doppler Radar
Primary Points
Radar: Radio Detection and Ranging
Gets information based on returned energy; radar emits energy, and if this energy strikes an
object (such as rain or snow), it scatters in all directions and a small fraction of it comes back to
the radar.
Conventional radar is mainly used to detect precipitation and how heavy said precipitation is.
Doppler Radar does this but can also detect wind direction and speed.
When looking for tornado formation, meteorologists usually look for opposing winds (winds in
opposite winds) that are close together on the Doppler radar. This is usually a sign that there is a
tornado forming in that area.
Radar rainfall estimates are made by multiplying the average rainfall rate by the duration over
which the rainfall was measured (Ex.-0.50 inches over 3 hours = 1.50 inches). Rainfall rate is
determined by drop diameter, the number of drops in the air, and the average drop fall speed.
Radar picks up anything that scatters back energy to it. This certainly means that rain and snow
are detected, but precipitation isn’t the only thing that can scatter energy.
Other things, such as radio waves, birds, and insects, can also appear on radar images and be
mistaken as some form of precipitation by the untrained eye.
NEXRAD (Next Generation Radar) extremely powerful-range of about 300 miles
The National Weather Service (NWS) has a network of about 160 Doppler radars, which covers
most of the U.S. Gives meteorologists a variety of tools to detect severe weather.
Trivia and Stories
February 26, 1935: The Daventry experiment
This was the first recorded detection of aircraft via radio waves
This experiment began the rapid development of radar
Technology would prove to be extremely useful in the next war
Sound Bites
“Radar: Serving Meteorologists and Bird Watchers Alike”
Doppler radar “may solve the tornado enigma”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://weather.noaa.gov/radar/radinfo/radinfo.html#diff
http://www.kdrv.com/doppler-radar-vs-traditional-radar/
http://www.crh.noaa.gov/Image/dvn/newsletters/Fall2006.pdf
http://www.meteor.iastate.edu/~jdduda/portfolio/HistoryPPT.pdf
El Nino/La Nina
Primary Points
Phenomena name: El-Nino Southern Oscillation (ENSO)
Warmer waters slosh (oscillate) back and forth across the Pacific Ocean like water in a bath tub.
Alternate between two states: El Nino and La Nina.
El Nino: causes above average sea surface temperatures in the central and eastern equatorial
Pacific.
La Nina: causes below average sea surface temperatures in the central and eastern equatorial
Pacific.
When temperatures are about average, it is known as ENSO neutral
El Nino: Weaker low-level winds at the Equator; effects strongest during the winter because
overall ocean temperatures are at their warmest, which causes the jet stream to become more
active over parts of the U.S. due to convection, which causes above average precipitation over
the southern U.S.; winter temperatures are usually cooler than usual in the southeast; increased
wind shear over the Caribbean and the Atlantic prevents tropical disturbances from developing
into hurricanes.
La Nina: Stronger low-level winds at the Equator; less active jet stream due to decreased
convection, causing below average precipitation for the southern U.S.; winter temperatures are
often warmer in the southeast and cooler in the northwest; upper level winds are light over the
Caribbean and the Atlantic, which creates more favorable conditions for hurricane development.
El Nino essentially releases heat from the tropics. Theory that if global warming is bringing more
heat to the earth overall, it could cause more El Nino events, which has been seen in the past.
Could create bigger rain and snow storms as a result (humid air pushed out of the tropics could
combine with air that is already more moist than normal).
Trivia and Stories
El Nino first noticed in the late 1800s.
Peruvian fisherman discovered that the normally chilly waters of the Pacific were replaced with
warm water.
Fewer fish and heavier rain in locations that were normally sunny.
Sound Bites
ENSO “is a child sloshing in the world’s bathtub”
Global warming “could birth an onslaught of El Ninos”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://www.nc-climate.ncsu.edu/climate/patterns/ENSO.html
http://www.ucar.edu/communications/quarterly/winter97/connection.html
Long-Range Weather Prediction
Primary Points
Mainly done using statistics and computer models
Rules are worked out using statistics; links future patterns to current climate.
Not much success with this technique at first, but a better understanding of ENSO and other
patterns has increased its reliability.
Pros: Easy to apply
Cons: Attempt to predict complex processes without any links to the physical and dynamical
processes; makes it good for large-scale developments that are already under way, but not so
good for sudden changes.
Computer models: more physically based; done using computerized general circulation models
(GCMs)
Process usually started by first predicting how the Pacific will behave.
Temperature patterns then used to predict how weather around the world will respond.
Improvements due to better models and better observations from the equatorial Pacific Ocean
Overall, methods are sound, but long-term forecasting still has many limitations and isn’t
extremely accurate.
Forecasts do vary seasonally; example: some places have the ocean to act as a stabilizing force,
which makes it easier to forecast long-term, while other landlocked areas are more susceptible to
short term climate fluctuations.
Old Farmer’s Almanac very vague, accommodates a wide range of weather; not really possible
to properly assess the book’s accuracy because of this.
When it takes a risk on testable predictions, it often fails
Trivia and Stories
1922: Lewis Fry Richardson made the first attempt to forecast the weather using calculations
Used a variation of Bjerknes’s primitive equations to do so
Calculated a 6-hour forecast by hand.
Forecasted the atmospheric state over two points in Central Europe
Took more than six weeks to calculate
Sound Bites
Old Farmer’s Almanac “is the shady fraud of the weather world”
Long-range forecasts “are bent, but not entirely broken”
Sources of Additional Info
http://www.wmo.int/pages/themes/climate/long_range_forecasting.php
http://www.washingtonpost.com/national/health-science/long-term-weather-forecasts-are-a-longway-from-accurate/2013/04/15/1f9a2ac8-a05b-11e2-be47-b44febada3a8_story.html
http://www.crh.noaa.gov/lot/forecast/lr_faq.php
Thunderstorms
Primary Points
Basic ingredients: moisture, rising unstable air (air that keeps rising when pushed upward), and a
mechanism to push the air upward. Surface is heated by the sun; if this warm air at the surface is
forced to rise (i.e. hills and mountains), it will keep rising as long as it is lighter and stays
warmer than the air around it. As this air rises, it brings heat from the surface to the upper levels
of the atmosphere (convection process) Water vapor in the air cools, releases heat, condenses and
forms a cloud. Process repeats and the cloud grows vertically into freezing air.
Ice particles are created in the freezing air, and when they collide they usually bounce off each
other. However, one particle can take ice from another particle and take electric charge with it.
Many collisions like this create large regions of electric charges, which causes lightning.
When lightning occurs, a channel of air is heated to 50,000 degrees. This creates a shock wave,
which in this case is a gust of superheated air moving away from the lightning at the speed of
sound. This is thunder.
More storms in spring/summer due to longer hours of daylight and sun’s higher position in the
sky, which brings more heat (necessary for air to rise)
Strength determined by amount of vertical wind shear (change in wind direction or speed with
height); more vertical wind shear provides the necessary access to warm, moist air for longer
periods of time. Severe storms: associated with high wind gusts, downpours, hail, and sometimes
tornadoes. Rotation within a storm is a telltale sign of severe weather.
Nighttime storms: occur after the maximum temperature occurs for the day; daytime heating can
increase the power of evaporation, and a great amount of moisture in the air can help to generate
powerful thunderstorms in the evening hours.
Trivia and Stories
1-year odds of getting struck and killed by lightning: 1 in 6.5 million
Contrast with lifetime odds of being killed by a cold: 1 in 6,165
Sound Bites
Lightning bolts “are all-consuming energy monsters”
“The cause of thunder: super hero or super heating?”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
https://www.nssl.noaa.gov/education/svrwx101/thunderstorms/
http://addins.wvva.com/blogs/weather/2013/03/why-are-thunderstorms-more-common-duringthe-spring-and-summer
http://www.tsgc.utexas.edu/stars/tslife.html
http://www.theweatherprediction.com/habyhints/185/
Climate Change
Primary Points
Greenhouse effect: Solar radiation is absorbed and re-emitted by greenhouse gas molecules and
clouds; warms Earth’s surface and the lower atmosphere.
Greenhouse gases: gases that absorb radiation and keep heat in the atmosphere; some occur
naturally (i.e. water vapor, carbon dioxide) and others are man-made (aerosol gases)
The issue of the earth’s warming trend is still highly debated; some still argue that the earth is
warming, but some are saying that the earth is actually cooling down.
Could be a “pause” in the warming
Potential causes of cooling: quiet solar cycle, volcanic activity, etc.
Some spikes of heat associated with El Ninos occurring, but warming trends have generally
decreased.
Still arguments as to the validity of the data (“cherrypicking” dates, inaccurate data, etc.)
Ozone hole and climate change aren’t the same thing, but there are some connections between
the two.
Chlorofluorocarbons (CFCs) destroy ozone molecules and are also greenhouse gases. However,
they’re in very small concentrations compared to other gases (such as carbon dioxide) and only
account for about 13% of the total energy absorbed by man-made greenhouse gases.
Ozone hole has a minor cooling effect (ozone in the stratosphere absorbs heat radiated to space).
Loss of ozone means more heat can escape into space.
Trivia and Stories
Starving young sea lions were found along the western coast of the United States
Warmer waters are driving their food source away from the islands where they breed and raise
their young; young sea lions are hunting for food themselves as a result.
Sound Bites
Trapping heat “is the newest sport amongst gases in the atmosphere”
Ozone hole “could be acting as a natural air conditioner”
Sources of Additional Info
http://oceanservice.noaa.gov/education/pd/climate/factsheets/whatgreenhouse.pdf
http://www.eia.gov/oiaf/1605/ggccebro/chapter1.html
http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2014/06/20/global-warming-ofthe-earths-surface-has-decelerated-viewpoint/
http://earthobservatory.nasa.gov/blogs/climateqa/are-the-ozone-hole-and-global-warmingrelated/
http://www.nytimes.com/2015/03/13/us/starving-sea-lions-washing-ashore-by-the-hundreds-incalifornia.html?ref=topics&_r=0
Winter Precipitation
Primary Points
Snow forms when the atmospheric temperature is 32 degrees Fahrenheit (0 degrees Celsius) or
below.
If ground temperature is 32 degrees Fahrenheit or below, snow will reach the ground, but can
still reach the ground at temperatures above 32 degrees Fahrenheit.
Snowflakes will start to melt as they reach the warmer layer, but this melting creates evaporative
cooling, which works to cool the air immediately around the snowflake and slow the melting
process.
Rain that fall when it is below 32 degrees Fahrenheit: freezing rain
Rain that falls through a small layer of cold temperatures at 32 degrees Fahrenheit or below;
freezes on contact on various surfaces.
Sleet: occurs during the winter; type of winter precipitation; snow goes through a warmer layer
as it falls and partially melts before falling through another cold layer. Freezes into an ice pellet;
only falls once.
Hail: occurs during severe weather (spring and summer, mostly). Forms when an object (dust, air
particles) collides with supercooled water. Forms an ice pellet; unlike sleet, it rises and falls
within a storm multiple times, accumulating more layers of ice until the updraft can no longer lift
it.
Difference between powdery snow and sticky snow: surface temperature Surface temperatures
just about freezing can melt snowflakes slightly and creating a stickier snow. Surface
temperatures below freezing don’t allow this melting to occur and create a powdery snow.
Ground can be above freezing while air temperature is below freezing, which will melt snow on
the ground (soil temperature hasn’t adjusted yet)
Trivia and Stories
Larger snowflakes can be up to 2 inches across and contain hundreds of individual crystals
Largest snowflake ever found: 8 inches by 12 inches (Bratsk, Siberia in 1971)
Sound Bites
Surface temperatures “make the final call on dry vs. wet snow”
Warmer temperatures “melt the icy hearts of snowflakes to create sleet”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://nsidc.org/cryosphere/snow/science/formation.html
http://earthsky.org/earth/all-about-freezing-rain
http://www.accuweather.com/en/features/trend/hail-or-sleet-how-to-tell-the-1/2930665
http://www.accuweather.com/en/features/trend/wet-vs-powdery-snow-2/5060689
http://www.theweatherprediction.com/habyhints/230/
Folklore
Primary Points
Come from observations and stories that have been handed down for many generations.
Haven’t been tested by the scientific method. Some are false, but many have some sort of
validity.
“Red sky at night…”: True. Red sky around dusk is usually the result of sunlight passing
through dust, salt, etc. Blue end of white sunlight spectrum is scattered more than the red by
these particles, which gives the sun its red appearance. High pressure is usually associated with
sinking air, which puts these particles closer to the ground and makes the red colors more
vibrant. However, a red sky in the morning (winds are blowing from the east or northeast)
usually means that mid or high level clouds are around. Atmosphere always moistens from top to
bottom, so the presence of these clouds usually means rain. “Ring around the sun/moon…”
True. One of the more reliable signs that a storm could be on its way. Atmosphere gains moisture
from top to bottom; first clouds to appear are cirrus (ice crystals at about 25,000 feet). These
bend white sun/moonlight to form a halo. The brighter the halo, the thicker the cirrus clouds. Not
entirely foolproof, but has a great deal of validity when combined with falling pressure.
Some good folklore: “Swallows high, staying dry; swallows low, wet will blow” (fair weather
brings sunshine which heats the ground and creates thermals, rising air that can carry insects
aloft, which forces birds to fly higher to get their food); “Cows lie down before a storm” (rapidly
falling pressure is said to have an effect on a cow’s digestive system, which creates discomfort.
Laying down seems to help alleviate this). Some bad folklore: “When the groundhog sees his
shadow, expect six more weeks of winter” (no real science behind this; makes for a fun event,
but no animal is really capable of predicting the weather that far in advance); “”When the wooly
bear caterpillar’s brown band is wide, a bad winter abides” (studies have been done to show that
the brown band on the wooly bear has nothing to do with weather and everything to do with
where the caterpillar grew up. Wide bands are associated with living in a wetter climate, whereas
smaller bands are associated with living in a drier climate).
Trivia and Stories
There’s a saying out that that says that tornadoes don’t occur in the mountains
Have been reported to occur above 10,000 feet
1987-violent tornado crossed the Continental Divide in Yellowstone National Park
Sound Bites
Red skies “generate a rather informative glow”
The groundhog “can be looked at as a shadowy fraud”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://www.erh.noaa.gov/rnk/Newsletter/Fall_2010/folklore.html
Lake (Sea)-Effect Snow / Rain
Primary Points
Lake effect rain happens when the air temperature is much cooler than the temperature of a
nearby lake. Colder air passes over warmer lake, air picks up moisture and drops it in areas
downwind.
Lake effect snow happens when cold air moves across warmer lakes in the winter. The air
becomes more humid and less dense and rises as a result, cooling as it does so. Cool, moist air
can form clouds, and once it is over land, it can condense and fall as snow.
Multi-band: Warm air over the lake rises and eventually condenses to form clouds. As the air
reaches buoyancy it will sink on both sides of the cloud, which creates an area without clouds
and a long strip of cumulus clouds. Clouds will line up lengthwise with the wind and may
precipitate.
Single band: Usually involve the entire length of the lake; form similar to multi-band storms, but
the process includes the entire lake. In other words, air warms and rises, reaches buoyancy, and
sinks on either side of the lake.
Single band storms are responsible for extremely large amounts of snowfall, sometimes on the
order of four feet or more of snow in a 24-hour period.
Ice on the Great Lakes causes lake-effect snow events to decrease significantly due to the water
being frozen and the cold air above not having access to any warmer water in the lakes.
Lake-effect rain is most common during the fall months (September-November)
Lake effect snow-rain not exclusive to the Great Lakes in the United States; can occur in other
locations as well.
Some other locations: Lake Baikal, Russia; west coasts of Honshu and Hakkaido, Japan
Trivia and Stories
September 14, 1996: Lake Erie was 73 degrees, but cooled to 43 degrees overnight
Had an effect on Erie County in New York, causing extensive flooding
Sound Bites
Multi-bands lake-effect storms “create spindly fingers of snow over land”
Single band lake-effect storms “descend upon towns in white walls of snow”
Sources of Additional Info
http://www.erh.noaa.gov/buf/ler.htm
http://www.miseagrant.umich.edu/lessons/lessons/by-broad-concept/earth-science/lake-effectsnow/
http://thevane.gawker.com/the-mechanics-behind-lake-effect-snow-natures-greatest-1659711094
http://www.islandnet.com/~see/weather/elements/lerains.htm
http://www-das.uwyo.edu/~geerts/cwx/notes/chap10/lake_effect_snow.html
Optical Phenomena
Primary Points
Rainbows form when rain is falling at the same time the sun is shining upon said drops.
Most of the sunlight that hits the raindrops passes directly through them, but some of it is
refracted into the component colors of the drops, reflected off of the back of the inside of the
drop, and refracted once more as it leaves the drop.
Drops smaller than 1/16 of an inch are the most effective for creating a rainbow (more spherical)
Not really common for rainbows to occur with snow; snowflakes don’t refract and reflect light
quite as efficiently as raindrops do (more chaotic patterns)
Can create optical phenomena, but usually smaller in size
Highway mirage: hot layer of air just above the ground; difference in refractive index (measure
of the bending of a ray of light when passing from one medium into another) between the hot air
at the surface of the road and the cooler, denser air above it makes the boundary between them
act like a mirror and reflects distant objects. “Water” is actually the reflection of the clear sky
and other things, such as cars and roadside grass.
Mirages in general generally require light to be bent through air that is at different temperatures.
Sun dogs are formed when light is refracted through horizontally-oriented hexagonal ice crystal
plates at a 22 degree angle; appear as bright spots (usually with color) around the same altitude
as the sun.
Other names for sun dogs: parhelia or “mock suns”
Haloes are formed when light passing through high-altitude clouds (i.e. cirrus) is refracted by the
ice crystals in them. Clouds must be between the observer and the light source.
Formation of these ice crystals requires temperatures to be 0 degrees Fahrenheit or lower.
Trivia and Stories
If light is bent twice as it enters the raindrops, a double rainbow will form.
Although rare, triple rainbows are also possible (light is bent three times)
Sound Bites
Rain “displays its artistry with the help of the sun”
Summer days “are a continual source of fake water and frustration”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
National Audubon Society Field Guide to Weather by David M. Ludlum
http://www.wral.com/weather/blogpost/1859390/
http://epod.usra.edu/blog/2010/03/highway-mirage.html
http://www.physics.org/article-questions.asp?id=45
Heat Index/Apparent Temperature
Primary Points
The heat index is the combined effect of temperature and relative humidity
Attempts to give a more accurate measure of how it will feel outside during the warmer months.
In order to determine the heat index, need to know the temperature and the relative humidity.
Heat index values in charts are actually only applicable for shady locations
If the area is exposed to direct sunlight, the heat index value can be increased up to 15 degrees
Fahrenheit.
Important for well-being of people; the more moisture the atmosphere has, the less people will
perspire, which decreases evaporation on the human body (evaporation is what keeps us cool
during the summer).
Therefore, if perspiration is not able to evaporate, the body can’t regulate its temperature.
This is why high heat index values can lead to a multitude of heat disorders with prolonged
exposure (Heat cramps, heat stroke)
Shortcomings: Only works under certain conditions (i.e. shady locations, light winds etc.)
Shortcomings: As said before, exposure to direct sunlight throws the index off, increasing values
up to 15 degrees Fahrenheit
Shortcomings: Wind can also have an effect on the heat index, particularly if they’re strong with
a great amount of hot, dry air; poses a higher risk to people working outside in the heat and also
bumps up values on the heat index.
Trivia and Stories
Hottest temperature on record in America: 134 degrees Fahrenheit in Death Valley on July 10,
1913.
Hottest temperature ever recorded on Earth: 136 degrees Fahrenheit in Al’Aziziyah, Libya in
September of 1922.
Heat index not just applicable to humans, but to animals as well; much lower to the ground, so
they heat up a lot faster than humans. Best to not leave them outside on hot surfaces, especially
on roads and sidewalks.
Sound Bites
Humidity “could spell the end for outdoor workers in the dead of summer”
Moisture “clogs skin pores and chokes the evaporative process”
Sources of Additional Info
Restless Skies: The Ultimate Weather Book by Paul Douglas
http://www.srh.noaa.gov/ama/?n=heatindex
http://www.aoml.noaa.gov/general/lib/heatw.html
Satellite Imagery/Data
Primary Points
Three basic types of satellite imagery: visible, infrared, and water vapor.
Visible: senses reflected solar radiation. Clouds, the atmosphere and the earth’s atmosphere all
absorb and reflect solar radiation Clouds appear white while other surfaces (land and sea) appear
as gray or black. Has a higher resolution than infrared imagery (0.6 miles), which means that it
can pick up smaller images in much better quality. Disadvantages: Only available during the
daytime hours because it relies on reflected sunlight to produce images.
Infrared: Creates images using re-emitted radiation in the form of heat. Once clouds, the
atmosphere and the surface absorb solar energy, the re-emit it as heat, which is what the satellite
senses. Works during the nighttime hours because it doesn’t rely on solar radiation like visible
imagery does. Disadvantages: Has a lower resolution (2.5 miles) than visible, so it can’t pick up
smaller features like visible imagery can.
Water vapor: type of infrared imagery; absorbs radiation at a certain wavelength and is used to
track the presence and movement of water vapor in the middle and upper atmosphere.
Allows meteorologists to track atmospheric motion that isn’t associated with clouds (can find
troughs and ridges possibly associated with developing storm systems); bright white (or brighter
colors) are associated with greater amounts of moisture, and darker grays and black (or darker
colors) as associated with a lack of moisture. Disadvantages: can’t really detect moisture in the
lower levels of the atmosphere (moisture in the middle and upper layers prevents detection of
moisture in the lower layers)
Can be used, for instance, to estimate rainfall amounts and thus predict potential floods.
Trivia and Stories
First pictures of Earth from space were taken on October 24, 1946
Taken from an altitude of 65 miles by 35-mm camera on a V-2 missile launched from the White
Sands Missile range. Pictures were grainy, but were some of the first steps towards progress with
satellite images.
Sound Bites
Sunlight “is the master of the visible satellite’s functionality”
Water vapor “creates a roadmap of the upper atmosphere”
Sources of Additional Info
http://www.goes.noaa.gov/sat-explanation.html
http://www.theweatherprediction.com/habyhints2/523/
http://www.researchgate.net/publication/223505068_Use_of_geostationary_meteorological_satel
lite_images_in_convective_rain_estimation_for_flash-flood_forecasting
http://www.airspacemag.com/space/the-first-photo-from-space-13721411/?no-ist