10 Weird Atmospheric Phenomena That'll Spook You

01
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Weird Weather

Orange lenticular Clouds at Sunrise.
UFOs? No, lenticular clouds over Death Valley Nat'l Park, California. Ed Reschke / Getty Images

Seeing something spooky is unnerving in and of itself, but seeing it in the atmosphere overhead is even more so! Here's a list of weather's ten most disturbing phenomena, why they freak us out, and the science behind their other-worldly appearance.

02
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Weather Balloons

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A high altitude scientific balloon. NASA

Weather balloons are infamous in popular culture, but unfortunately not for their weather monitoring purposes. Thanks largely to the 1947 Roswell incident, they've become objects of UFO sighting claims and cover-ups. 

Odd Looking, But Perfectly Safe

In all fairness, weather balloons are high-altitude, spherically-shaped objects that appear shiny when lit by the sun -- a description that fits that of unidentified flying objects -- except that weather balloons couldn't be more routine. NOAA's National Weather Service launches them everyday, twice daily. Balloons travel from Earth's surface up to a height of about 20 miles collecting weather data (like air pressure, temperature, humidity, and wind) in the middle and upper portions of the atmosphere and relaying this information back to weather forecasters on the ground to be used as upper-air data.

Weather balloons aren't just mistaken for questionable aircraft while in flight, but also when on the ground. Once a balloon travels high enough up in the sky, its inside pressure becomes greater than that of the surrounding air and it bursts (this typically happens at altitudes exceeding 100,000 feet), scattering debris on the ground below. In an attempt to make this debris less mysterious, NOAA now labels its balloons with the words "Harmless Weather Instrument."

03
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Lenticular Clouds

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Lenticular clouds over the Andes Mountains in El Chalten, Argentina. Cultura RM/Art Wolfe Stock/Getty Images

With their smooth lens shape and stationary movement, lenticular clouds are frequently likened to UFOs.

A member of the altocumulus family of clouds, lenticulars form at high altitudes when moist air flows over a mountain peak or range resulting in an atmospheric wave. As air is forced upward along the mountain slope, it cools, condenses, and forms a cloud at the wave's crest. As the air descends the lee of the mountain, it evaporates and the cloud dissipates at the wave's trough. The result is a saucer-like cloud which hovers over the same location for as long as this airflow setup exists. (The very first lenticular to be photographed was over Mt. Rainier in Seattle, WA, USA.)

04
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Mammatus Clouds

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Mammatus loom above the traffic below. Mike Hill/Getty Images

Mammatus clouds give the expression "the sky is falling" a whole new level of meaning. 

Upside-Down Clouds

While most clouds form when air rises, mammatus are one rare example of clouds forming when moist air sinks into dry air. This air must be cooler than the air around it and have a very high content of liquid water or ice. The sinking air eventually reaches the bottom of the cloud, causing it to protrude outward in rounded, pouch-like bubbles. 

More: 6 Must-know facts about clouds

True to their ominous appearance, mammatus are often harbingers of a coming storm. While they're associated with severe thunderstorms, they're merely the messengers that severe weather may be around -- they are not a type of severe weather itself. Nor are they a sign that a tornado is about to form. (Both of these are popular misconceptions!)  

05
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Shelf Cloud

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Shelf clouds over southern Colorado. Cultura Science/Jason Persoff Stormdoctor/Getty

Is it just me, or do these ominous, wedge-shaped cloud formations resemble the descent into Earth's atmosphere of every extraterrestrial "mothership" ever depicted in sci-fi film?

Shelf clouds form as warm, moist air is fed into a thunderstorm's updraft region. As this air rises up, it rides up and over the downdraft's rain-cooled pool of air which sinks to the surface and races out ahead of the storm (at which point it is called the outflow boundary or gust front). As the air rises along the gust front's leading edge, it tilts, cools, and condenses -- forming an ominous looking cloud that protrudes from the thunderstorm base.

06
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Ball Lightning

1886 depiction of ball lightning ("The Aerial World" by Dr. G. Hartwig). NOAA

Less than 10% of the U.S. population has reportedly witnessed ball lightning -- a free-floating red, orange, or yellow sphere of light. According to eye witness accounts, ball lightning can either descend out of the sky or form several meters above ground. Reports differ when describing its behavior; some mention it acts as a fireball, burning through objects, while others refer to it as a light that simply passes through and/or bounces off of objects. Seconds after forming, it is said to either silently or violently extinguish, leaving the smell of sulfur behind.

Rare and Largely Undocumented

While it is known that ball lightning is related to thunderstorm activity and usually forms alongside cloud-to-ground lightning strikes, little else is known as to the reason for its occurrence.

07
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Aurora Borealis (Northern Lights)

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The Aurora Borealis near Yellowknife, NT, Canada. Vincent Demers Photography/Getty Images

The Northern Lights exist thanks to electrically charged particles from the sun's atmosphere entering (colliding) into Earth's atmosphere. The color of the auroral display is determined by the type of gas particles that are colliding. Green (the most common auroral color) is produced by oxygen molecules.

08
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St. Elmo's Fire

1886 drawing of St. Elmo's fire ("The Aerial World" by Dr. G. Hartwig). NOAA

Imagine looking outside during a thunderstorm to see a bluish-white orb of light appear out of nowhere and "sit" at the end of tall, pointed structures (such as lightning rods, building spires, ship masts, and airplane wings) St. Elmo's Fire has an eerie, almost ghost-like appearance.

The Fire That's Not a Fire

St. Elmo's fire is likened to lightning and fire, yet it isn't either. It's actually what's called a corona discharge. It occurs when a thunderstorm creates an electrically charged atmosphere and air's electrons group together creating an imbalance in electrical charge (ionization). When this difference in charge between air and a charged object gets large enough, the charged object will discharge its electrical energy. When this discharge happens, air molecules essentially tear apart, and as a result, emit light. In the case of St. Elmo's Fire, this light is blue because the combination of nitrogen and oxygen in our air. 

09
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Hole Punch Clouds

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A "hole punch" cloud observed over Mobile, AL, December 11, 2003. Gary Beeler/NOAA NWS Mobile-Pensacola

Hole punch clouds may be one of the least odd named on this list, but they're nonetheless vexing. Once you spot one, you're sure to spend many a sleepless night wondering just who or what cleared that perfectly oval-shaped hole smack-dab in the middle of an entire cloud. 

Not as Extraterrestrial as You Might Think

While your imagination may run wild, the answer couldn't be less fanciful. Hole punch clouds develop inside layers of altocumulus clouds when airplanes pass through them. When a plane flies through the cloud layer, local zones of low pressure along the wing and propeller allow the air to expand and cool, triggering the formation of ice crystals. These ice crystals grow at the expense of the cloud's "supercooled" water droplets (small liquid water droplets whose temperatures are below freezing) by pulling moisture out of the air. This reduction in relative humidity leads the supercooled droplets to evaporate and disappear, leaving behind a hole. (Because ice crystals are capable of growing at a slightly lower relative humidity than water droplets, they continue to form. This is how wispy cirrus clouds end up in the midst of the cloud hole.)

10
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Lightning Sprites

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A red sprite above the white light of an active thunderstorm over Central America - August 10, 2015. NASA, Expedition 44

Named for the mischievous sprite "Puck" in Shakespeare's A Midsummer Night's Dream, lightning sprites form high above a surface thunderstorm in the atmosphere's stratosphere and mesosphere. They're linked to severe thunderstorm systems having frequent lighting activity and are triggered by the electrical discharges of positive lightning between the storm cloud and the ground. 

Oddly enough, they appear as jellyfish, carrot, or column-shaped reddish-orange flashes.

11
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Asperatus Clouds

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Undulatus asperatus above Tallinn, Estonia in April 2009. Ave Maria Moistlik/Wiki Commons (http://creativecommons.org/licenses/by-sa/3.0)

Resembling a CGI or post-apocalyptic sky, undulatus asperatus wins the award for creepiest cloud, hands down.

Harbingers of Meteorological Doom?

Besides the fact that it commonly occurs across the Plains region of the United States following convective thunderstorm activity, little else about this "agitated wave" cloud type is known. In fact, as of 2009 it remains a proposed cloud type only. If accepted as a new species of cloud by the World Meteorological Organization, it'll be the first to be added to the International Cloud Atlas in over 60 years.