Atmosphere

Table of Contents

Introduction

The atmosphere is the layer of gases, commonly known as air, that surrounds the Earth and is retained by Earth’s gravity. It protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (via the greenhouse effect), and reducing temperature extremes between day and night.

This Viking 1 orbiter image shows the thin atmosphere of Mars. The mountains of the southern Argyre Basin is visible, with Galle crater left of center. Viking image number is 040A63. The photo was taken through red color filter.

Composition of the Atmosphere

The Earth’s atmosphere is composed primarily of nitrogen (about 78%) and oxygen (about 21%), with trace concentrations of water vapor, carbon dioxide, argon, and other gaseous molecules.

Layers of the Atmosphere

The atmosphere is divided into five main layers, each with distinct characteristics:

Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

Troposphere

This is the lowest layer of the atmosphere where we live. It extends up to about 8 kilometers at the poles and about 18 kilometers at the equator. This layer is characterized by a decrease in temperature with height. Weather phenomena occur in this layer.

Stratosphere

The stratosphere extends from the top of the troposphere to about 50 kilometers above the Earth’s surface. The ozone layer, which absorbs most of the Sun’s harmful ultraviolet radiation, is located in this layer. The temperature in the stratosphere increases with height.

Mesosphere

The mesosphere extends from the stratosphere to about 85 kilometers above the Earth. This layer is characterized by a decrease in temperature with height. Meteors burn up in the mesosphere.

Thermosphere

The thermosphere extends from the mesosphere to about 600 kilometers. The temperature in this layer increases with height. This layer includes the region of the atmosphere known as the ionosphere, which extends from about 60 kilometers to more than 1,000 kilometers above the Earth.

Exosphere

This is the outermost layer of the Earth’s atmosphere. It extends from the top of the thermosphere to about 10,000 kilometers. In this layer, atoms and molecules escape into space and satellite orbits occur.

Atmospheric Pressure

Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface. It decreases exponentially with altitude. The equation for the pressure at a given height in the atmosphere is given by the barometric formula:

$P = P_0 e^{-\left(\dfrac{g h}{R T}\right)}$

where $P$ is the atmospheric pressure at height $h$ , $P_0$ is the atmospheric pressure at sea level, $g$ is the acceleration due to gravity, $R$ is the specific gas constant, and $T$ is the temperature.

Climate and Weather

The atmosphere plays a key role in the Earth’s climate and weather. Various atmospheric processes involving heat transfer, the water cycle, and the movement of air masses lead to phenomena like winds, clouds, rain, and storms. Understanding these processes is crucial in meteorology and climatology.

Conclusion

The Earth’s atmosphere is a complex and dynamic system, crucial to sustaining life. Understanding its composition, structure, and the physical processes within it is key to many fields, including meteorology, climatology, and aviation.

Do you prefer video lectures over reading a webpage? Follow us on YouTube to stay updated with the latest video content!

Want to study more? Visit our Index here!

Introduction

Composition of the Atmosphere