Video - SCRIPT OF NARRATION
Water falls from the sky as rain or snow. It sits on the
ground in puddles. We see it on grass early in the morning
as dew. When you look at Earth from a satellite in
space, you see that most of it is covered with water in the
oceans. Look closer and you will see big lakes and rivers.
Over the land and over the oceans, we see clouds, and in
many places that are cold, we see snow. The clouds and
snow are made of water too so water is everywhere.
People use water to drink and to stay clean. Plants use
water to grow. Without water we would not be able to live.
Water is called a liquid because you can pour it and it will
change shape. If you put it in a glass, it takes the same
shape as the glass. If you pour it on the ground, it spreads
out and becomes flat. Liquids can move and change
shape.
If you pour water into an ice tray and put it in a freezer,
you can turn it into ice. When water turns into ice, we call
it a solid. A solid is something that is hard and does not
change shape. You can touch it and see it, but even if you
put it into a glass, it still keeps the same shape. Put it on
a counter and it also stays the same. Of course, if you let
ice stay out long enough, it will melt and become water
again.
But what happens when you leave water out for a long
time? It disappears. Where does it go? Into the air.
Invisible water that floats in the air is called water vapor.
We also call it moisture, or humidity. You can't see water
vapor, but sometimes you can feel it when the air is warm
and sticky. Warm air can hold more water vapor than cold
air. When the tiny droplets leave the water to float into the
air, we call that evaporation.
Once evaporation lets water vapor float in the air, the
water is not a liquid anymore because you can't pour it.
It's not a solid because you can't see it. Now, it's called a
gas. A gas is something that you can't see or touch and it
floats with air.
Water is very special because it can be a solid, like ice; a
liquid, like rain; or a gas, like water vapor.
Even in the driest parts of the world, there is water vapor.
Wind spreads it around the planet. It's in the air and you
don't see it until it makes clouds. When you get enough
water vapor together, it grows and forms clouds. Weather
forecasters call this condensation.
Condensation happens when invisible water in the air
grows large enough for us to see. Put a cold glass on a
table and watch it. You'll see water droplets grow on the
outside of glass. These water droplets came from water
vapor in the air.
This happens on clear, quiet mornings when you see dew
on the grass. When the dew forms, use a thermometer to
read the temperature, then you know what the dew point
temperature is. The dew point temperature just tells you
how cold the air has to be for condensation to make dew.
When the air is very cold, instead of seeing dew, you
might see frost.
In the morning, you can tell dew apart from rain because
rain makes everything wet. Dew will only wet cars,
rooftops, grass, and a few other things. Dew comes from
moisture in the air. Rain comes from clouds.
Clouds make rain, snow, sleet, or hail. All of these are
called precipitation. Precipitation is any kind of water that
falls from the clouds. In the winter, cold clouds make snow
and sleet. In the summer, clouds make rain because the
air is warm, but if the cloud is very tall, it might reach high
enough into the sky where the temperature is cold, and
then make hail. Hail is small pieces of ice that fall from tall
thunderclouds.
Precipitation, evaporation, and condensation are always
happening over and over. These three things never stop,
so we call it the water cycle. The water cycle has no
beginning and no end.
Precipitation falls to the ground and makes puddles.
Some of the water goes into streams and rivers and then
to the oceans. The sun heats Earth to make evaporation
happen. That's when water turns into invisible water
vapor. Wind moves the water vapor around as condensation
turns it back into clouds. When the clouds get too full,
the precipitation starts again.
The water cycle makes sure that there is always water
moving around the world. Even when we can't see water
and even when it is frozen into snow or ice, the water
cycle takes moisture everywhere.
The part of the water cycle that we always see is the
beautiful clouds. They float above our heads in all
shapes, sizes and colors. Sometimes they are so gentle
that we don't really notice them, but other times they grow
so large that you just can't miss them.
There are four kinds of clouds: cirrus, stratus, cumulus,
and cumulonimbus.
Cirrus clouds are very high thin clouds. They are so thin
that you can see the sun or the moon right through them.
They can be more than five miles, or eight kilometers,
above the ground - that's higher than where most airplanes
fly. Cirrus clouds are gentle, soft and feathery.
They are not thick enough to make precipitation; so when
you see them, you know that the weather is calm.
Stratus clouds are lower clouds that are flat, stretched
out, and gray. They can cover the whole sky and hide the
sun. Stratus clouds can make rain or snow. Sometimes
they stay for more than a day. If they stay for a long time,
you might get a lot of rain or a lot of snow. They might also
make very light rain called drizzle. In the winter, stratus
clouds can make light snow called flurries. When they
block the sun, stratus clouds keep you from getting warm.
A special kind of stratus cloud is fog. Fog is a cloud that
is close to the ground. If you ever want to know what a
cloud feels like, just go outside on a foggy day. You can't
feel the cloud, but you will feel the moisture. It will make
the air damp. Sometimes fog is only a few feet, or meters,
thick. Other times, it can be thousands of feet or thousands
of meters thick and cause problems because drivers
can't see very well and airplanes can't take off or land.
Fog happens a lot in some places where you have water.
Cumulus clouds are fluffy and puffy and they grow tall.
They look like cotton balls as they bubble up into the air.
Small cumulus clouds with lots of space in between them
tell us the weather will be nice. The larger and taller
cumulus clouds make rain showers, or snow showers if it
is cold enough. The showers usually don't last very long.
When cumulus clouds make lightning, thunder and heavy
rain they are called cumulonimbus. The cumulonimbus is
the tallest cloud. Sometimes it can reach more than tenmiles, or 16 kilometers, high. It's the cloud that makes
thunderstorms. When you see a cumulonimbus cloud,
you have to make sure that you are safe from lightning,
and from the heavy rain. Cumulonimbus clouds can make
a lot of rain in one spot to start a flood. Floods are dangerous
to people. Floods also wash away soil and we call
that erosion. You can do an experiment using sponges
and a spray bottle to show that when rain falls slowly the
ground is able to soak it up but when it falls too fast the
ground can't hold all of it and it rises to make a flood.
Always stay away from floodwater.
Clouds are part of the water cycle. They help the Earth by
moving water around. When clouds get thick, they block
the sun and keep us cool in the daytime. At night, thick
clouds act like a blanket over the Earth and help to keep
us warm.
Clouds come from condensation. You can make your own
cloud in a jar. Just fill the jar with warm water, cover it with
plastic, and then put an ice cube on top of the plastic.
Look closely inside the jar and after a while, you'll see
condensation making a cloud.
Many of us make clouds and don't even notice it. The next
time you take a shower, look around the bathroom to see
what is floating in the air. When you get out of the shower
look at the mirror. What do you see?
One of the trickiest parts of forecasting the weather is
knowing when a cloud will start to make rain. You can
practice with your friends by using a cotton ball, water and
an eyedropper. Count how many water drops the cotton
ball can hold before the water starts falling out. Then try it
again with another cotton ball. Do you get the same number?
Probably not, because no two clouds are the same.
The nice thing about clouds and the water cycle is that
when you add sunlight to them, you see many pretty
shapes and colors.
Cumulus clouds are bright and crisp when they are away
from you but when they are over you, they look dark
because the cloud blocks the sunlight.
When rain ends in the afternoon and the sun comes out
you might see a rainbow. Look for a curve of colors in the
sky. The rainbow tells you that the rain is over.
Cirrus clouds also make something that looks like a rainbow.
It's a ring around the sun called a halo. Most people
don't notice them because they don't take the time to stop
and look up into the sky. Sometimes on the sides of the
halo you'll see two bright spots that have a lot of color.
These are called sun dogs.
At sunset, all of the different clouds help to show magnificent
colors. We can see red, orange, yellow, purple and
sometimes other colors. Without clouds and the water
cycle we would have a pretty boring sky.
The clouds are nature's way of giving us art. Enjoy the
water cycle and stay weather smart.