In this topic you will learn about Earth's atmosphere and temperature.

As Earth travels around the Sun, the Sun's rays strike the surface of Earth at different angles. Insolation means the amount of the Sun's energy that reaches Earth at a given place and time. The position of Earth in the path of the Sun's light affects the angle of insolation and the amount of solar energy received by Earth. Dark-colored, rough materials absorb more solar energy than light-colored, smooth materials. The same amount of light energy will heat land to a higher temperature than water.

Altitude also affects the temperature of the atmosphere. The atmosphere is the blanket of gases that surrounds Earth. The troposphere is the layer of the atmosphere closest to Earth's surface. It is the first layer of the atmosphere. In this layer, as altitude increases, the temperature decreases. In the next layer of the atmosphere, called the stratosphere, the temperature increases as altitude increases. The layer above the stratosphere is the mesosphere. Here the temperature decreases as altitude increases. In the uppermost layer, the thermosphere, the temperature increases as altitude increases.

Air pressure is the force put on a given area by the weight of the air above it. The layers of air pressing down on Earth's surface cause air pressure. Air pressure is also affected by altitude. As the altitude increases, the air pressure steadily decreases. Normal air pressure is greatest at sea level.

In the lower atmosphere, the composition of air varies only a little. In higher elevations, the air is a mixture of gases, water vapor, and dust particles.

Weather refers to the conditions in the lower portions of the atmosphere at any given place and time. Air temperature, air pressure, water in the air, and wind affect weather.

Air temperature is measured with a thermometer. Fahrenheit, F, and Celsius, C, temperature scales are commonly used. Air pressure is measured with a device called a barometer.

Knowing about the weather and how you are affected by it helps you take precautions and protect yourself.