Is a measure of how much water vapor is in the air.

It is measured in a percent using a psychrometer.

More humidity means more clouds and more likely chance of precipitation.

This forms clouds!

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Clouds form when the water vapor reaches the dew point.Remember that as you go up in the troposphere, the temperature decreases.

Dew point

This is the reason clouds look to be about the same height in the sky and flat on the bottom. They are!

Dew point temperature is reached.

If the dew point temperature is the same as the air temperature on the ground, fog forms! The cloud actually forms on the ground.

Any form of H2Othat falls from clouds

and reaches the earth's surface.

The term rain is restricted to drops of water that fall from a cloud and have a diameter of at least 0.5 millimeter.

Drizzle and mist have smaller droplets.

The most common form of precipitation is rain.

Drizzle droplet

Mist droplet

Cloud droplet

As water vapor collects into larger and larger droplets, gravity will cause them to fall to the ground as rain, sleet, hail, or snow.

Form when water vapor condenses to form drops of liquid water or ice crystals.

There are three main types of clouds.

Cirrus – high, thin, feathery cloudsMade of ice crystals

Cirrus – highest type of cloud. Due to elevation, made of ice crystals. They indicate that a change in the weather is coming.

Cumulus – round, puffy cloudsIndicate fair weather

They can build up to form storm clouds that contain hail, lightning, and tornadoes.

Cumulonimbus clouds often produce bad weather (lightning and hail) Nimbus/nimbo means rain. Notice that it is getting flat on the top. That means the top of the cloud has reached the top of the troposphere and cannot go any higher.

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Cumulonimbus

Stratus – flat layer of clouds. Often have rain.

Nimbostratus clouds often produce rain for many hours. Like stratus clouds, they cover the sky. The only difference is that these are producing rain or snow.

Other cloud types