Chapter 1 Lesson 2

How are atmospheric conditions measured?

Almost all weather occurs in the lowest level of the atmosphere. Weather- condition of the atmosphere at any

moment.

The atmosphere stretches about 1000 km (620 miles) from Earth’s

surface to outer space.

The lowest layer (troposphere) of the atmosphere, the troposphere, is where

most water is found and where most clouds form.

The troposphere is about 15km (9 mi. ) thick at the equator. Very little weather occurs above the

troposphere.

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In the stratosphere, little water is present, so there are only a few

clouds. From this layer up to space, there is no water and little

air for any weather to occur.

Weather changes because the atmosphere is constantly changing. As air warms, air pressure lessens. Warm

air holds more water and has more humidity.

A thermometer measures temperature. (degrees)

Air pressure is the weight of the atmosphere. A barometer measures air pressure.

A rain gauge measures the amount of precipitation (rain, snow, sleet, or hail). (centimeters)

A hygrometer measures the amount of humidity (water).

A wind vane measures the direction from wihich the wind is blowing. (kilometers)

An anemoter measures the wind’s speed.

The atmosphere pushes on you all the time and in all directions. There are

several types of barometers for measuring air pressure. One is the

mercury barometer.

Let’s check B14 to see how it works.

In addition to temperature and air pressure, humidity, or the amount of water in the air, is an important factor in describing weather.

This transferring of water from the Earth surface to the atmosphere and back is called the water cycle.

On clear nights when the surface of the Earht cools quickly, water vapor may condense to form a cloud near the

ground. This low cloud is called fog.

Whether clouds form on the ground or high in the atmosphere, it forms in the same way.

Even though all clouds form by condensation, different types of

atmospheric conditions produce different types of clouds. Weather scientists, or meterologists give clouds three basic

names.

Cirrus clouds are high clouds made mostly of ice crystals.

They look thin and crispy.

They’re usually associated with fair weather, but may mean a change in weather is coming.

Cumulus clouds form when large bubbles of warm air rise rapidly into the atmosphere.

They are puffy.

They usually mean fair weather, but can produce light rain or snow showers.

Stratus clouds form as a mass of warm air is slowly pushing upward over a mass of colder air or over a mountain.

Stratus means layer. They look like a layer.

They often produce rain or snow.

Chapter 1 Lesson 3

What role do oceans play in the water

cycle?

Almost all of the water that covers the earth is ocean water. Even though ocean water is salty, it provides most of Earth’s fresh

water.

Earth’s water is always being recycled. Heat from the sun

causes fresh water to evaporate from the oceans,

leaving salt behind.

The water condenses to form clouds. Fresh water falls from

Earth’s surface as rain.

Water in the water cycle changes from a liquid to a gas and back

to a liquid.

The water cycle also includes the sun, the water, the air, and the

land

Ocean water is a mixture of water and many dissolved

solids

Most of these solids are salts. Sodium Chloride is the

most common salt.

You probably know this as table

salt.

Salts and other substances in the ocean come from the

land. Runoff slowly breaks down the rocks that make it

up

In places where rivers empty into oceans, the ocean water is less salty. This is because

fresh is mixed with salty.

Ocean water is a little saltier near the equator, where it is

hot and water evaporates faster

Ocean water is a little less salty near the North and

South Poles, where it is colder and water evaporates more

slowly.