99 Fun Facts About Cloud

Which amateur meteorologist proposed the Latin cloud-naming system in 1802?

Luke Howard made chemicals for a living and watched the sky as a hobby; his cloud names so delighted Goethe that the poet wrote verses in his honour.

What does the Latin word 'cumulus' mean?

Heap or pile: the same Latin root gives us 'accumulate', and a cumulus is just that, warm moist air heaping upward until it shows as cloud.

The name of the high, wispy cirrus cloud comes from a Latin word meaning what?

Curl or fringe: to the Romans a cirrus was a curl or lock of hair, which is why the name went to the thin, trailing streaks that weather-watchers call mare's tails.

The cloud name 'stratus' comes from a Latin word meaning what?

Layer: stratus literally means spread out or laid down, the same root that gives geologists the strata of rock they read like pages.

In cloud names, which prefix marks a cloud of the middle level of the sky?

Alto- comes from the Latin for high, yet it labels the middle deck: the clouds above it take cirro-, and low clouds carry no height prefix at all.

Clouds look white because their water droplets scatter which part of sunlight?

All colours equally: cloud droplets are about as big as light waves, so they scatter every colour alike and the blend looks white, whereas the far smaller molecules of clear air favour blue.

The flat top of a mature thunderstorm cloud marks where its rising air meets which boundary?

The tropopause is where the air stops getting colder with height, so the storm's updraft loses its lift and spreads sideways; it sits about 9 km up at the poles and 17 km at the equator.

By international definition, fog is cloud at ground level that cuts visibility to below what distance?

1 kilometre is the line agreed internationally, mainly for aviation; British public forecasts are far stricter and only say fog when you can see less than 180 metres.

Which fishing grounds off Newfoundland are often called one of the foggiest places on Earth?

The Grand Banks get their fog when warm air off the Gulf Stream drifts over the cold Labrador Current, the same meeting of waters that made them one of the world's richest fishing grounds.

Which clouds, forming in the mesosphere about 80 km up, are the highest on Earth?

Noctilucent clouds are so high that they still catch the Sun after dark, and they appear in summer, which is oddly when the air at that height is at its coldest.

The highest clouds on Earth were first recorded in 1885, two years after which volcanic eruption?

Krakatoa had filled the sky with dust in 1883, so when the strange clouds were first reported two summers later people blamed the volcano; the link has never been proven.

Mammatus clouds, the pouches hanging under a storm cloud, take their name from the Latin word for what?

Udder or breast: the pouches form when cold air sinks out of the storm's overhang, the reverse of the upward growth that builds most clouds.

Which smooth, stationary clouds that form downwind of mountains are often mistaken for UFOs?

Lenticular clouds sit in the crests of standing waves that mountains set up in the wind, like ripples below a rock in a river, so they hover in place while the air rushes through them.

'Contrail' is short for what?

Condensation trail: a jet's hot, moist exhaust freezes into ice crystals in the cold air at cruising height, just as your breath turns white on a winter's day.

Which chemical, found to seed clouds by Bernard Vonnegut in 1946, is still widely used to make them rain?

Silver iodide works because its crystals are built so much like ice that supercooled droplets freeze onto them; its discoverer was the elder brother of the novelist Kurt Vonnegut.

In 1946 Vincent Schaefer ran the first cloud-seeding experiments by dropping what into supercooled clouds?

Dry ice worked by sheer cold: Schaefer had put a lump in his laboratory freezer to chill it faster, then watched his own breath turn into millions of ice crystals.

Which Olympic host city fired rockets at rain clouds to try to keep its opening ceremony dry?

Beijing fired 1,104 rockets from 21 sites around the city on the evening of its 2008 ceremony to make the clouds rain early; officials called it a success, though scientists dispute how well it worked.

The Cloud Appreciation Society's manifesto pledges to fight what 'wherever we find it'?

Blue-sky thinking is the manifesto's joke with a point: Gavin Pretor-Pinney founded the society in 2005 to argue that life would be dull under cloudless monotony day after day.

Weather observers report how much of the sky is covered by cloud in which unit?

Oktas are eighths of the sky: 0 is clear and 8 is overcast, yet the scale runs to 9, the code for a sky that cannot be seen at all, usually because of fog.

Which wave-like, 'underwater'-looking cloud was added to the International Cloud Atlas in 2017?

Asperitas got in after a campaign by citizen scientists: members of the Cloud Appreciation Society kept photographing a cloud nobody could name, and their founder proposed one.

The Morning Glory, a roll cloud up to 1,000 km long, is regularly seen from Burketown in which country?

Australia's Gulf of Carpentaria is the one place where the cloud turns up predictably, and each spring glider pilots travel to tiny Burketown to surf its rising front with their engines off.

What often punches a fallstreak hole, the neat round gap also called a hole-punch cloud?

A passing aircraft chills the air around its wings or propellers enough to freeze some of the cloud's supercooled droplets; the ice then spreads, falls out as a streak and leaves the hole.

Nacreous clouds, named for their mother-of-pearl colours, form in which layer of the atmosphere?

The stratosphere is so dry that clouds can form there only in the deep cold of the polar winter; lit from below the horizon, they go on glowing long after sunset.

The thick clouds that hide the surface of Venus are made mainly of droplets of which acid?

Sulphuric acid clouds bounce back about three-quarters of the sunlight that reaches Venus, which is why the planet outshines everything in our sky except the Sun and Moon.

What is the scientific study of clouds called?

Nephology is the branch of meteorology devoted to clouds; add one letter and you get nephrology, which is the medicine of the kidneys.

Which Athenian playwright mocked Socrates in The Clouds, a comedy first staged in 423 BC?

Aristophanes had Socrates dangle in a basket to study the sky, but the joke fell flat on the day: the play came last of the three comedies at that year's festival.

Tiny dust, salt or smoke particles that cloud droplets form around are called what?

Condensation nuclei are about a hundredth the size of the droplets that grow on them, so every cloud droplet has a speck of dust, soot or salt at its heart.

Clouds form when air is cooled to which temperature?

Its dew point can be reached two ways: the air can cool, usually by rising, or it can pick up enough extra moisture to be saturated at the temperature it already has.

According to NASA, low, thick clouds have which net effect on the temperature of Earth's surface?

Cooling: low, thick clouds bounce sunlight back to space before it can warm the ground, while thin, high clouds do the opposite, letting sunlight in and trapping the heat that tries to leave.

A 'flammagenitus' cloud is one created by what?

Large fires or volcanic eruptions heat the air so fiercely that the cloud above can grow into a thunderstorm of its own, whose lightning and violent winds then spread the fire further.

A rotating 'wall cloud' at the base of a supercell, which can spawn tornadoes, is formally named what?

Murus is Latin for wall: the storm's updraft draws in humid air from its rain area, which turns to cloud lower down than the rest of the base, so the wall hangs below the storm.

Iridescent clouds get their rainbow colours from which optical effect?

Diffraction: droplets of nearly the same tiny size bend sunlight around themselves and fan it into pastel bands, whereas large ice crystals refract it and make halos instead.

Which company, later bought by Hewlett-Packard, used the phrase 'cloud computing' in a 1996 business plan?

Compaq's plan is the earliest known use of the phrase in print; its authors pictured business programs moving onto the web, and for Compaq it led to a business selling servers to internet providers.

Which company released S3 storage and the EC2 compute cloud in 2006, launching modern cloud computing?

Amazon was known as an online shop when it began renting out computing power; its customers came to include Netflix, which runs on Amazon's servers while competing with Amazon's own video service.

In cloud computing, what does the first 'S' in SaaS stand for?

Software as a service runs on the provider's computers and reaches you through a web browser, which is why programs once bought in a box are now rented by subscription.

Chicago's mirrored sculpture Cloud Gate, nicknamed 'The Bean', is the work of which artist?

Anish Kapoor modelled the shape on a drop of liquid mercury; its mirror skin reflects the clouds overhead, and the arch you can walk under is the 'gate' of the title.

Roll clouds are formally known by which Latin species name, added to the Cloud Atlas in 2017?

Volutus means rolled: the tube forms where a wave of cool air, such as the outflow of a storm, lifts warm, moist air ahead of it, and it seems to turn slowly on its axis as it travels.

Most clouds on Mars are thin wisps made of which substance?

Water ice makes up most Martian clouds; in 2008 a lander even watched snow fall from them over the planet's frozen desert, though it vanished before it touched the ground.

Which cloud type contains ice crystals whose interactions produce hail and lightning?

Cumulonimbus clouds charge themselves: soft hail and tiny ice crystals collide in the updraft, each bounce trading a little charge, until the cloud holds enough to fire lightning.

Around 340 BC, which Greek philosopher wrote Meteorologica, summing up ancient weather knowledge?

Aristotle's title comes from the Greek for the study of things high in the air, the word that still names the science, and his account remained an authority on weather for nearly 2,000 years.

Ground-level condensation that still leaves visibility above the fog threshold is called what?

Mist is fog's thinner twin, the same suspended water droplets at a lower density, whereas haze is not water at all but a veil of dry particles too small to see.

What is the name for rain or snow that evaporates before it ever reaches the ground?

Virga shows as grey streaks trailing under a cloud; the evaporating rain chills the air around it, which can then plunge to the ground as a sudden microburst, a danger to anything flying nearby.

The pale top deck of Jupiter's clouds is thought to be made of frozen crystals of which substance?

Ammonia ice tops the stack; below it NASA expects a deck of ammonium hydrosulphide crystals and, deepest of all, clouds of plain water, the same stuff as Earth's.

The Cloud Atlas label 'homogenitus', as in cumulus homogenitus, comes from Latin words meaning what?

Man-made: the homo here is Latin for man, not Greek for same, and the label covers clouds born of human activity, from jet contrails to the plumes above power stations.

The anvil-shaped top of a big thunderstorm cloud carries which Latin feature name?

Incus is Latin for anvil, which is why anatomists gave the same name to the anvil-shaped bone of the middle ear; the cloud's top flattens where its updraft runs out of lift.

Stratus cataractagenitus is a cloud generated by spray from what?

Waterfalls can make their own weather: the plunging water drags air down with it, and the air that rises nearby to replace it carries the spray up, where it condenses into cloud.

Breaking-wave clouds caused by wind shear are named for Lord Kelvin and which German physicist?

Helmholtz showed why the boundary between two streams of fluid cannot stay smooth: where fast air slides over slower air it curls into breaking waves, a cloud feature now called fluctus.

Which French naturalist published a cloud-naming scheme in 1802 that used everyday French names rather than Latin?

Jean-Baptiste Lamarck sorted clouds into types such as hazy, dappled and broom-like; he is far better remembered for arguing, half a century before Darwin, that species change over time.

What is the name for the smooth cap cloud that can form over the top of a rising cumulus?

Pileus is Latin for a cap: it forms when a fast-rising cloud shoves the moist air above it upward, so a pileus is a sign that the cloud beneath is growing quickly and may turn stormy.

According to the US Geological Survey, the water in one typical cumulus cloud weighs about how much?

1.1 million pounds, about 500 tonnes, is the USGS figure. The cloud floats anyway because its moist air is less dense than the drier air underneath it.

Aotearoa, a Māori name usually translated as 'land of the long white cloud', refers to which country?

New Zealand got the name, in one traditional story, when the family of the explorer Kupe spotted a cloud on the horizon before the land beneath it came into view.

Which US city's summer fog has its own name, Karl, borrowed from a giant in the film Big Fish?

San Francisco's fog became Karl in 2010, when an anonymous Twitter account began posting in its voice. The name caught on across the city.

Which flowers does William Wordsworth come upon beside a lake in his poem 'I Wandered Lonely as a Cloud'?

Daffodils lined the shore of Ullswater in the Lake District when Wordsworth walked there with his sister Dorothy, whose journal recorded the sight.

Which storybook bear rolls in mud and floats up on a balloon, posing as a little black rain cloud?

Winnie-the-Pooh hopes the muddy disguise will fool the bees guarding a hive. Disney's 1966 film gave him a song for the ride, 'Little Black Rain Cloud'.

Cloud City, the floating gas-mining colony in The Empire Strikes Back, is run by which smooth-talking character?

Lando Calrissian welcomes Han Solo's party as guests, then hands them to Darth Vader, who had threatened to put the city under Imperial control.

Rippling rows of small, high cloudlets that resemble fish scales give a sky nicknamed after which fish?

Mackerel sky comes with its own rhyme, 'not twenty-four hours dry', because the rippled pattern is taken as a sign that the weather is about to change.

A funnel cloud hanging beneath a storm officially becomes a tornado at the moment it does what?

Touches the ground is the test: a funnel that never reaches the surface is not counted as a tornado, although the winds below it are often spinning before it arrives.

A six-sided cloud pattern wider than Earth has swirled for decades around the north pole of which planet?

Saturn's hexagon was found in images from the Voyager flybys of the early 1980s, and each of its sides is longer than the diameter of Earth.

In the British version of the old weather rhyme, a red sky at night is said to be whose delight?

Shepherd's delight has science behind it: in Britain a red sunset usually means high pressure moving in from the west, bringing a dry day to follow.

In the water cycle, what is the collective name for rain, snow, sleet and hail falling from clouds?

Precipitation does not include fog, whose droplets stay hanging in the air instead of falling to the surface.

Which invisible gas in the air turns into the tiny liquid droplets that make up a cloud?

Water vapour reaches the sky mostly by evaporating from oceans, lakes and rivers, and it stays unseen until the air chills enough for droplets to form.

In a weather forecast, which single word describes a sky completely covered by a grey sheet of cloud?

Overcast has a mirror-image term: pilots looking down on the same unbroken deck from above report it as an undercast.

Fair-weather cumulus clouds often sit on top of rising columns of sun-warmed air known by what name?

Thermals in a steady wind line their clouds up in long rows, which glider pilots call cloud streets and follow to stay aloft.

Almost all of Earth's clouds and weather are found in which lowest region of the atmosphere?

The troposphere is far deeper over the tropics, about 18 km, than over the poles, about 6 km, and it holds roughly 80% of the atmosphere's mass.

Why do cloudy winter nights usually stay milder than clear, starry ones in the same place?

Clouds trap escaping heat like a blanket, sending the warmth the land gives off back down; under a clear sky it leaks away to space and frost can form.

Which thick, dark grey blanket of cloud brings hours of steady rain or snow but no thunder or lightning?

Nimbostratus usually signals a warm front, whose rain is steadier and longer-lasting than the short, heavy downpours of a cold front.

Which thin, milky veil of high cloud often betrays itself only by a bright halo around the Sun or Moon?

Cirrostratus can be a warning: when it spreads across the sky behind wispier high cloud, a warm front and rain may follow within a day.

Bright patches of light that flank the Sun when it shines through icy high cloud go by which nickname?

Sun dogs sit about 22 degrees either side of the Sun, level with it above the horizon, and show best when it is low in the sky.

Wispy, hooked streaks of cirrus drifting high in the sky are traditionally nicknamed after which animal feature?

Mare's tails are streamers of heavier ice crystals falling out of the cloud, dragged into hooks by the changing wind beneath.

The 'tablecloth', a sheet of cloud that pours over the flat top of Table Mountain, hangs above which city?

Cape Town legend says the tablecloth is smoke from a pipe-smoking contest between the Devil and a local pirate called Van Hunks.

The Monteverde reserve, a cloud forest famed for its orchids and almost constant low cloud, is in which country?

Costa Rica drew the Quaker farmers from Alabama who settled at Monteverde in 1951 because it had abolished its army three years before.

Haar, a cold sea fog that rolls onto the east coasts of Scotland and northern England, comes in off which sea?

The North Sea stays cold into summer, so warm air drifting over it between April and September turns to fog that can push several miles inland.

In northern Chile, the village of Chungungo once drew its drinking water from coastal fog using rows of what?

Mesh nets stood upright in the fog catch droplets that trickle down into a trough, and a pipeline carried the water down the mountain to Chungungo.

Which Indian state, home to some of the wettest places on Earth, has a Sanskrit name meaning 'abode of clouds'?

Meghalaya joins the Sanskrit megha, cloud, and alaya, abode; parts of its Khasi Hills record about 12 metres of rain a year.

The 'spectre' that hikers see when their giant shadow falls on cloud below them is named after which German peak?

Brocken, the highest peak of the Harz, is fogbound so often that the apparition became a local legend; the shadow only looks enormous through a trick of perspective.

A fogbow looks white instead of rainbow-coloured because fog droplets differ from raindrops in what way?

They are far smaller, under 0.05 mm across, so the bands they make smear into one another and the bow comes out pale, earning it the name white rainbow.

Fog that forms when warm, moist air drifts sideways over a colder sea or land surface is known as what kind?

Advection fog covers most sea fogs; radiation fog, by contrast, forms over land on calm, clear nights after sunset.

Shafts of sunlight that fan out through gaps in cloud, nicknamed Jacob's ladder, have which formal name?

Crepuscular rays are really almost parallel; they only seem to spread apart because of perspective, like the edges of a long straight road.

Long, narrow clouds that criss-cross satellite images of the open ocean are seeded by particles from what?

Ship exhaust gives moisture extra particles to gather on, and the wind stretches the result into a bright line of cloud that marks each vessel's route.

The Large and Small Magellanic Clouds, bright smudges in southern night skies, are actually what kind of object?

Dwarf galaxies in orbit round the Milky Way, the pair look to the naked eye like torn-off pieces of it, and were reported by a chronicler on Magellan's voyage.

The Oort cloud, a vast shell of icy bodies at the Solar System's edge, is thought to be the source of what?

Long-period comets fall inward from the cloud, which the Dutch astronomer Jan Oort proposed in 1950 to explain why the Sun never runs out of them.

On Titan, the only moon with a dense atmosphere, clouds rain down mainly which liquid hydrocarbon instead of water?

Methane does on Titan what water does on Earth, forming clouds and raining out to fill rivers, lakes and seas, the only stable surface liquid known on another world.

The Pillars of Creation, towering clouds of gas and dust photographed by Hubble, lie in which star-forming region?

The Eagle Nebula lies some 6,500 to 7,000 light-years away; the 1995 image became one of Hubble's best-known pictures, and the Webb telescope shot the same pillars again in 2022.

Sagittarius B2, a gas cloud near the centre of the Milky Way, holds a chemical that helps flavour which fruit?

Raspberries owe part of their taste to ethyl formate, which astronomers detected in the cloud, prompting reports that the heart of the galaxy smells of raspberry rum.

Which airport weather instrument shoots a laser straight up to measure the height of the cloud base?

A ceilometer sends laser pulses lasting only nanoseconds and times their echo off the cloud; the height it reports is what pilots call the ceiling.

Roughly how many tiny cloud droplets have to collide and merge before one raindrop is heavy enough to fall?

Millions are needed because a single cloud droplet is far too small to fall, which is why most clouds drift past without shedding a drop.

Operation Popeye, a secret US cloud-seeding campaign, tried to prolong the monsoon over which wartime supply route?

The Ho Chi Minh Trail was meant to turn to mud: the squadron that flew the missions from 1967 to 1972 worked under the slogan 'make mud, not war'.

The cloud chamber, which shows charged particles as streaks of droplets, was invented by which Scottish physicist?

C. T. R. Wilson got the idea on the summit of Ben Nevis in 1894, where light effects in the mountain clouds set him trying to recreate them in a laboratory.

NASA's CloudSat satellite mapped the water and ice inside clouds from orbit using which sensing technology?

Radar let CloudSat measure the height and make-up of clouds; after a battery fault in 2011 it could run only in sunlight, and the radar was switched off for good in 2023.

Which Olympian god was known to the ancient Greeks by the title 'cloud-gatherer'?

Zeus once put the skill to devious use, shaping a cloud into a double of his wife Hera to snare the mortal Ixion.

A pillar of cloud by day and one of fire by night first guide the Israelites in which book of the Bible?

Exodus gives the cloud a second job: when Pharaoh's army catches up at the Red Sea, the pillar moves behind the Israelites and leaves the Egyptians in darkness.

Which British band topped the charts on both sides of the Atlantic in 1965 with 'Get Off of My Cloud'?

The Rolling Stones wrote it as a grumble about the pressure to follow 'Satisfaction', and Keith Richards later said the record had been rushed.

Cloud Strife, who battles the Shinra corporation and his old colleague Sephiroth, is the hero of which video game?

Final Fantasy VII was built around Cloud from the start: after an earlier game with several leads, its makers wanted one identifiable hero.

Which singer-songwriter painted her own portrait for the cover of Clouds, her 1969 album featuring 'Both Sides, Now'?

Joni Mitchell wrote 'Both Sides, Now' after reading a Saul Bellow novel on a flight, at a passage where its hero looks down at clouds from a plane.

In Greek myth, a cloud nymph sent a winged ram to rescue her son Phrixus; which hero later sailed after its fleece?

The Golden Fleece hung in a sacred grove in Colchis, where Phrixus had sacrificed the ram, until Jason and the Argonauts stole it.

Which English landscape painter called his habit of making weather-annotated studies of clouds 'skying'?

John Constable noted the weather, the light and the time of day on the back of each sketch, and called the sky the 'chief organ of sentiment' in a landscape.

Clouds that form when wind is forced to rise over a mountain range are described by which term?

Orographic lift wrings rain out on the windward slopes, which is why the far side of a range often lies in a dry rain shadow.

Which German poet so admired the new Latin system for naming clouds that he wrote verses thanking its inventor?

Goethe also tried to commission the painter Caspar David Friedrich to make cloud studies based on the system, but Friedrich declined.

Which actor leads the 2012 film Cloud Atlas with Halle Berry, playing a different character in each era?

Tom Hanks plays six characters in stories set between 1849 and 2321, in a film directed jointly by the Wachowskis and Tom Tykwer.