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Name: Shannon
Status: student
Grade: K-3
Location: NJ
Country: N/A
Date: 4/1/2005


Question:
What causes rain?


Replies:
Shannon,

The temperature in a cloud is so low that the air is saturated or even super-saturated with water, meaning that it can hardly hold the water in it. The water droplets that make up the cloud start growing, using the extra water in the wet air of the cloud. Sometimes there is a lot of air movement in the cloud (particularly in a thunderstorm) and the droplets hit each other and form bigger droplets. When the droplets get so large that gravity starts pulling them downwards, they might grow even larger still by hitting and combining with other droplets. They then fall out of the cloud as rain drops and fall to the ground as rain.

David R. Cook
Atmospheric Physics and Chemistry Section
Environmental Research Division
Argonne National Laboratory


Dear Shannon

Look, when mom washes clothes and hangs them at the backyard and the day is hot enough what happens with the water that still is dripping? (of course it is easier to put the clothes in a dryer, but just suppose she does not have one) Well, in due time the water goes away and the clothes get dry. And the water goes where?

Think a bit.

It goes into the air!

So, now think about all the water that are over earth surface forming the oceans, rivers, lakes and so on.

When the day is hot, or even if it is not too hot, it is enough the sun rays falling over all that water make part of it to go into the atmosphere. So some water is said "to evaporate".

What happens with all that evaporated water? Look above at the sky, if you are lucky you are going to see some clouds. Some dark clouds, some gray clouds, some white ones. The clouds are made with the evaporated water.

There are different kinds of clouds . The gray ones have many little droplets of water and are ready to come back to earth as rain!

During winter time they can come down as snow also. So everything does a full turn and come back over the soil and also come down over oceans, rivers and lakes...

Thanks for asking NEWTON!

Mabel Rodrigues


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