☁️ What is a Cloud? Crash Course Geography #10 - Free Educational videos for Students in K-12

☁️ What is a Cloud? Crash Course Geography #10 - By Math and Science

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00:0-1	before . There were weather satellites and sophisticated forecasting technology
00:03	. Clouds were the best way to predict what weather
00:05	was coming . Clouds high up in the sky .
00:07	Or no clouds at all meant fine weather , but
00:09	clouds moving low in the sky or dark clouds .
00:11	Rain was on its way . Common sayings even sprung
00:14	up from our cloud observations like red sky in the
00:16	morning . Sailor's warning red sky at night , Sailor's
00:19	delight . And there are many more across time in
00:22	different cultures . Today , geographers and meteorologists still rely
00:25	on clouds to forecast the weather by studying how and
00:28	why they form clouds . Give us important information on
00:30	the temperature and amount of moisture in the atmosphere ,
00:32	which can help us predict weather from cloud this summer
00:35	afternoons to overcast winter mornings . More than that ,
00:38	a map of the worlds , clouds tells us about
00:40	today's energy flows and weather patterns and unlocking the mysteries
00:43	of clouds will help us better understand how the atmosphere
00:45	is warmed . So today we'll join countless peoples throughout
00:48	history and look up at the clouds . I'm al
00:51	. Is a career , and this is crash course
00:53	geography . Yeah , clouds are often described with dramatic
01:03	words like ethereal or ominous . They seem alive born
01:06	from the atmosphere , appearing as mysterious objects like UFOs
01:10	. But clouds are also useful atmospheric data . Clouds
01:13	are basically big water buckets floating in the atmosphere .
01:16	They're composed of billions of so small they're invisible water
01:19	droplets and ice crystals too small to form raindrops ,
01:21	so they stay suspended in the atmosphere . In fact
01:24	, each cloud has its own anatomy , height ,
01:26	name and reason for being kind of like an atmospheric
01:29	person . Sailors of your and scientists of today know
01:31	that clouds can tell us more than whether it might
01:33	rain . For example , we often see a villainous
01:35	type of cloud hanging over cities called Smog . A
01:38	London physician first coined the word smog in 1900 to
01:41	describe the combination of smoke and fog the layer of
01:44	cloud on the ground that cast a pall over the
01:46	city . Smog pollution that harms our lungs , irritates
01:49	our eyes and throat and even corrode structures over long
01:51	periods of time . It also traps extra heat in
01:54	the atmosphere contributing to human caused global warming . But
01:56	the presence or absence of clouds can make a big
01:58	difference in the amount of energy that reaches the surface
02:00	of the earth to let's go to the thought bubble
02:03	to meet them . As modern storm chasers were ready
02:05	to drive for hours to document unique cloud formations and
02:08	send data back to local meteorologists . We have to
02:11	know who we're dealing with . But luckily the vast
02:13	majority of clouds are classified into three types based on
02:16	the way they look . The first clouds we spot
02:18	our wispy tendrils of white . These cirrus clouds ,
02:20	or mayors tails are made up of ice crystals and
02:23	they only exist way high up above 6000 m .
02:25	Cirrus clouds like these reflect 50% of insulation or incoming
02:29	solar radiation . But they're even better at trapping long
02:32	wave radiation trying to move back out to space insulating
02:35	and warming the Earth's atmosphere is part of the natural
02:37	greenhouse effect . Miles down the road , the sky
02:39	is filled with dull gray , flat horizontal layers of
02:42	low level clouds below 2000 m stratus clouds like these
02:46	reflect and scatter about 90% of insulation , which cools
02:49	the earth by keeping incoming energy from reaching the ground
02:52	. You can blame them for the dreary weather .
02:53	We keep driving as the weather clears , but now
02:56	we notice lumpy cumulus clouds taking over the sky ,
02:58	cumulus clouds are signs . The energy in the atmosphere
03:01	is shifting around because they can be so thick and
03:03	reach so far high up into the atmosphere . They
03:06	generally reflect as much energy away from the earth as
03:08	they absorb to warm here . So they're basically neutral
03:11	in terms of warming the atmosphere . If we're lucky
03:13	driving through this hot afternoon , we'll see the bright
03:15	, lumpy cumulus clouds keep growing higher and thicker now
03:19	the rain is picking up and we found our storm
03:21	, the rain or nimbus form of cumulus clouds ,
03:24	cumulonimbus clouds are towering rain clouds , which showcase a
03:27	powerhouse of energy exploding as big storms . Thanks thought
03:30	bubble to climate scientists . Understanding clouds and how energy
03:34	flows through them is critical to understanding how our earth
03:37	warms and cools and how climate change . While serious
03:40	clouds only appear at high levels , stratus and cumulus
03:42	clouds can appear at any level and cloud names actually
03:45	describe this . So just like people can be complex
03:48	, we could have say lumpy cumulus clouds growing in
03:50	the middle above 2000 m but below 6000 m at
03:53	the Aalto level . These are called alto cumulus .
03:56	Or we could have horizontal stratus clouds way high above
03:59	6000 m , forming icy cirrus stratus layers , serious
04:03	or the prefix zero means high level , also refers
04:06	to the mid level and low level clouds are just
04:08	plain stratus or cumulus , maybe with a nimbus tacked
04:11	on if it's raining but no matter where or what
04:13	they are , clouds naturally cool and heat the lower
04:15	atmosphere . Though how much depends on the altitude cloud
04:18	type amount of cloud cover and thickness . Basically if
04:21	we imagine clouds is floating water buckets . Each type
04:23	holds different amounts of water and clouds are just one
04:26	phase of the hydrological cycle that circulates water between the
04:29	atmosphere , the hydro sphere , the little sphere and
04:31	the biosphere clouds tie the atmosphere and hydro sphere together
04:34	. By the way to form clouds , water has
04:35	to enter the atmosphere through evaporation , which is when
04:38	liquid water molecules absorb enough heat to become energized and
04:41	break away from the surface is water vapor . The
04:43	water vapor stores . This extra energy is latent heat
04:46	of evaporation for a gram of liquid water to turn
04:48	into water vapor , it absorbs 585 calories , which
04:51	for us would be like eating five largest bananas .
04:54	This is why when sweat evaporates from our bodies ,
04:56	it usually has a cooling effect . The liquid water
04:59	absorbs some heat from our bodies and some water molecules
05:01	turn into vapor humidity describes how much water vapors in
05:04	the air . In general , the air at high
05:06	latitudes , like the arctic and the antarctic is naturally
05:08	colder because of less sunlight , so it has much
05:10	less water vapor and is less humid . Places like
05:13	the caribbean or other tropical and equatorial regions of earth
05:15	have hotter air with more water vapor and more humidity
05:18	. Because water vapor can store energy is latent heat
05:20	of evaporation , humidity is linked to how much energy
05:23	is available in the atmosphere to produce weather . So
05:26	low humidity is part of why we don't usually hear
05:28	about devastating weather events , like hurricanes coming down from
05:30	the arctic , and we can sense humidity on a
05:32	personal level , because hair lengthens as humidity increases and
05:35	contracts as humidity decreases . I know a thing or
05:38	two about that in weather reports on the news when
05:40	they talk about a warm front moving in and 55%
05:43	humidity outside back to you , Barbara . they're actually
05:47	talking about relative humidity . Relative humidity is a comparison
05:50	between the actual amount of water vapor in the air
05:52	and how much could be in the air when air
05:54	at a certain temperature is at 100% relative humidity ,
05:57	it contains the maximum amount of water vapor possible .
06:00	So it's saturated , like a sponge full of water
06:03	that can't soak up anymore unless you squeeze it out
06:06	. Except squeezing water out of the atmosphere is rain
06:09	. Any kind of humidity strongly depends on the air
06:11	temperature and how much moisture is available at higher temperatures
06:14	. It's more likely that more liquid water molecules will
06:16	have the energy to evaporate into water vapor and float
06:19	around in the atmosphere . So in hotter areas ,
06:22	the air can hold more water . Of course ,
06:24	just because warm air can hold more water doesn't mean
06:26	that there's always water vapor around inland regions like the
06:29	central Sahara desert are very dry because they're far from
06:32	the oceans and there's not a lot of liquid water
06:34	available to be evaporated . But let's say we're staying
06:36	in a cabin by a lake , so there's plenty
06:38	of liquid water around The same relative humidity can feel
06:41	very different depending on the air temperature . On a
06:43	hot day , 70% relative humidity can feel heavy ,
06:46	sticky and uncomfortable , almost like standing in a cloud
06:49	because the air can hold more total water , 70%
06:52	of saturation is a lot of vapor . Plus when
06:54	we're hot , we sweat and when there's a ton
06:56	of moisture already in the air are sweat can't evaporate
06:58	as easily . So we're stuck feeling damp on a
07:01	cold day , 70% relative humidity is much more comfortable
07:04	because the colder air can hold less water . So
07:06	70% of saturation isn't as much water vapor Plus It's
07:10	cooler , so we don't need to sweat . As
07:11	much changing temperatures can also change the relative humidity ,
07:14	even if the amount of moisture stays the same ,
07:17	like during the day it might be sunny and hot
07:19	and the relative humidity is only at 50% . But
07:21	as the sun sets and temperatures drop at night ,
07:23	the air has a harder time holding onto the water
07:25	vapor . By morning it feels very damp and dewdrops
07:28	form on the grass . We've reached 100% saturation even
07:32	though no extra water vapor was added to the air
07:34	during the night we reached the dew point , which
07:36	is the temperature when water vapor can condense back into
07:38	liquid droplets , given the current amount of water vapor
07:41	in the air like as dew on the grass or
07:42	fog , which is really just a cloud on the
07:44	ground . So at the dew point are metaphorical sponge
07:47	would be full and a cloud can be born .
07:49	If we compare dry regions such as the Sahara desert
07:51	to a human regions such as Mississippi , it takes
07:54	a lot more cooling to reach the dew point and
07:56	get condensation in the desert than it does in Mississippi
07:58	. Even though water vapor and liquid water are just
08:00	two different arrangements of water molecules , it's nearly impossible
08:03	for condensation to happen if there's no surface for a
08:05	water droplet to cling to like the outside of a
08:08	cold soda can . So there's one key ingredient of
08:10	clouds that we haven't mentioned yet condensation nuclei . These
08:13	are microscopic particles like sea salt spray , dust ,
08:16	smoke , pollen and volcanic material in the atmosphere that
08:19	provide a surface for condensation to take place as trillions
08:22	of our water molecules cling to specks of dust and
08:25	form billions of tiny liquid water droplets and sometimes freeze
08:28	into ice crystals . After that we get a cloud
08:31	. So I guess clouds are more like a big
08:32	bucket of dusty water . The condensation phase of the
08:35	hydrological cycle releases all the stored up energy in that
08:38	water vapor for every gram of water , 585 calories
08:42	or five largest bananas are freed as the latent heat
08:45	of condensation . So if a small puffy cumulus cloud
08:47	holds 500 to 1000 tons of moisture droplets , that's
08:51	a tremendous amount of energy being released that can power
08:53	a storm . Every cloud is really the result of
08:55	Cooley . We've only described in general how clouds form
08:58	from water molecules being energized and evaporating before convincing into
09:01	liquid droplets in the atmosphere , but so much more
09:04	goes into creating the unique panoramas that fill the sky
09:07	. Each cloud is one of a kind , just
09:09	like , even though we can generalize about how people
09:11	are born and grow up , there are so many
09:13	intricacies that make a person who they are , even
09:15	whether our cloud will be a small puffy cumulus cloud
09:18	or an ominous cumulonimbus cloud depends on so many factors
09:21	like the specific temperature and humidity of the initial air
09:24	and changing atmospheric conditions as our evaporated water molecules rise
09:28	and with 50% of the earth covered by clouds at
09:30	any given moment , there are so many possible shapes
09:33	and sizes . It's no wonder clouds are such an
09:35	ever changing and beautiful aspect of our environment . All
09:38	of these elements come together to deeply affect the earth
09:40	and us humans to , we've paid attention to clouds
09:43	for thousands of years , not just because of their
09:45	beauty , but because they absorb scatter and reflect rays
09:48	from the sun , influence the global energy budget and
09:52	circulate the key ingredient for life around the globe ,
09:54	but more on that and raindrops next time . Thanks
09:58	for watching this episode of Crash Course Geography , which
10:00	was made with the help of all these nice people
10:03	. If you'd like to help keep Crash Course free
10:04	for everyone forever , please join our community on Patreon
10:17	. Yeah .

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