Kind: captions
Language: en
most of the time if we pay attention to
clouds at all it's because of their
effect on our local weather
or maybe it's because they make a sunset
prettier
but what you might not know is that
clouds affect us every day
even if we're staring at a clear blue
sky the clouds we see when we look out
the window are important components of a
complex global weather system
they play a key role in earth's water
cycle carrying huge amounts of fresh
water and dropping it as precipitation
and depending on their properties and
where and when they form clouds can have
dramatic effects on our climate
influencing the locations and severity
of floods and droughts and even the
temperature of our planet as a whole
so by understanding clouds we can better
predict severe storms the global
distribution of fresh water and the
course of climate change
but what exactly are clouds and how do
they form
all clouds share the same basic
ingredient
water
they're made up of water droplets or ice
crystals that have formed from water
vapor in the atmosphere
although you can't see it or feel it the
air around us contains water even on the
clearest summer day
the main sources of this vapor are
evaporation which is the escape of water
molecules from the surface of oceans
lakes and soil and transpiration the
release of water by plants
as the sun warms earth's surface heat is
transferred into the atmosphere along
with water vapor
the warmer the air the more moisture it
can hold
but warm air doesn't usually stay near
the surface for long
like a hot air balloon it rises
as it does it cools
the colder the air becomes the less
water vapor it's able to hold
if the air becomes cold enough it
reaches a state called supersaturation
which causes some of the water vapor to
transition back to a liquid or solid
state
water molecules in the vapor form around
tiny particles of dust ice sea salt and
pollution
suspended in the atmosphere
these particles called condensation
nuclei serve as the starting point for
the formation of water droplets and ice
crystals
with this final step repeated billions
and billions of times the water that's
been in the atmosphere all along is
suddenly visible
and a cloud is born
while we can now see the cloud the
individual droplets or ice crystals are
tiny which is why they remain airborne
but they can combine to form larger
drops or crystals and if they become
large enough and too heavy to stay aloft
they'll fall as rain snow sleet or hail
back to earth's surface where the water
in them came from originally