Chapter 7: Atmosphere and Climate. Section 7.1: Atmosphere Section 7.2: Climate

The one thing that makes life possible on Earth is the atmosphere. The atmosphere is the thin layer of gases around the Earth.

The atmosphere is 78% nitrogen, 21% oxygen, and the remaining 1% is composed of water vapor, carbon dioxide, argon, neon, helium, and other gases.

Important functions of the atmosphere Provide the air needed for respiration, and photosynthesis. Protects living things from the sun’s harmful UV rays and other stellar objects. Allows light to reach the Earth’s surface. Radiates heat back to the Earth – keeping the planet warm.

Living things played an important role in forming the Earth’s atmosphere. With the use of photosynthesis, plants converted carbon dioxide and water into food – giving off oxygen.

As the plants multiplied, the amount of oxygen in the air began to increase.

Atmospheric Pressure Gravity holds the gases of the atmosphere near Earth’s surface. As a result, the air molecules are compressed together and exert force on Earth’s surface. The pressure exerted is called atmospheric pressure – and is exerted equally in all directions – up, down, sideways.

Atmospheric Pressure Most of these air molecules are found within the first 16 miles of the atmosphere, but they become increasingly thinner as one travels farther from the Earth’s surface.

Atmospheric Pressure Atmospheric pressure can change as a result of differences in temperature and in the amount of water vapor in the air. The reason this can occur is that warm air causes molecules to spread out forcing air pressure to drop. Also, warm air holds more water vapor than cold air. Water vapor has less mass than atmospheric oxygen and nitrogen.

Atmospheric Pressure Similarly, air that contains a lot of water vapor is less dense than drier air, because water vapor molecules have less mass than nitrogen or oxygen molecules do.

Atmospheric composition

The Earth’s atmosphere is composed of five layers; as you move from the surface each layer becomes less dense.

TROPOSPHERE Extends from the Earth’s surface 16 km. Contains 90% of the atmospheric gases. The part of the atmosphere which contains the weather. Also contains the air currents.

STRATOSPHERE Extends from 17-48 km. Commercial air liners often travel in the lower part of the stratosphere. It contains the ozone.

Mesosphere- extends from 49-80 km. Millions of meteors burn up daily in the mesosphere as a result of collisions with some of the billions of gas particles contained in that layer leading to a high concentration of iron and other metal atoms,

Thermosphere Extends from 80 –500 km Absorbs high amounts of solar radiation. Do to the absorption of solar radiation, radio waves from the Earth’s surface bounce off this layer and return to Earth.

Thermosphere and Radio Waves

EXOSPHERE Extends out from 500-600 km. Becomes thinner and thinner until the exosphere merges with outer space. Contains satellites.

Atmospheric Temperatures

Weather/ Climate

What is weather? It is simply what is happening in the atmosphere at a particular time and place.

It is the average weather in an area over a long period of time. What is climate? It is the average weather in an area over a long period of time.

Climate is determined by a variety of factors including latitude, air circulation, ocean currents, and the local geography of an area.

Latitude It is the distance from the equator. It strongly influences climate because the amount of solar energy an area receives depends upon its latitude.

Atmospheric Circulation Patterns There are three properties of air that contribute to air circulation:

1. Warm air rises and cools as it rises.

Cool air sinks and as it sinks it warms.

Warm air is capable of holding more water than cool air.

Ocean Circulation Patterns They have a major impact on climate because water holds great amounts of heat. Oceans tend to make climates more moderate.

Local Geography Depending upon the altitude determines the climate for specific areas of the world.

What causes seasons? The Earth’s orbit around the sun is the cause of the seasons. The Earth is tilted at about 23 degrees. This tilt means that the angle at which the sun’s rays strike the Earth changes as the Earth moves around the sun.