Atmosphere and Climate

Overview of Earth's Atmosphere

The Earth is surrounded by a protective layer of air called the atmosphere. This atmospheric shield makes life on Earth possible by providing essential oxygen and protecting living organisms from harmful rays. Furthermore, it helps maintain a suitable temperature environment required for the survival of living beings. Meteorological phenomena, including weather and climate, are directly connected to underlying atmospheric conditions.

General Structure and Physical Properties of the Atmosphere

The atmosphere is divided into distinct structural layers categorized by variations in temperature and density. These layers are arranged sequentially one above the other. As altitude increases and one moves upward, the air becomes progressively thinner. The density of air reaches its highest level near the Earth's surface and decreases with increasing altitude. Throughout these regions, the atmosphere contains a mixture of gases that are essential for life.

Troposphere

The Troposphere is the lowest layer of the atmosphere, extending directly above the Earth's surface. It lies between $00\,km$ and $12\,km$ above the Earth's surface, though its boundary altitude varies geographically: it extends to a height of $8\,km$ at the poles and reaches up to $18\,km$ at the equator. The upper boundary marking the limit of the Troposphere is called the Tropopause. Most weather changes, such as rainfall, storms, and cloud formation, take place within this layer. Additionally, the Troposphere contains approximately $75\%$ of all air in the entire atmosphere.

Stratosphere

The Stratosphere is situated directly above the Troposphere, lying between $12\,km$ and $50\,km$ above the Earth's surface. This layer contains the ozone layer, which absorbs incoming solar radiation. Consequently, the temperature within the Stratosphere increases with height due to this absorption of solar radiation by ozone. Because of its stable air conditions, aeroplanes often fly in this layer. The upper boundary defining the top of the Stratosphere is called the Stratopause.

Mesosphere

The Mesosphere lies between $50\,km$ and $80\,km$ above the Earth's surface. It is recognized as the coldest layer of the atmosphere. Within the Mesosphere, temperature decreases with high altitude. Most meteors burn up in this layer due to friction generated upon interaction with air particles. The upper boundary of the Mesosphere is called the Mesopause.

Thermosphere

The Thermosphere is positioned above the Mesosphere and is also known as the Ionosphere due to the presence of electrically charged particles. This layer plays a crucial role in radio communication by reflecting and sending back radio waves back to Earth. In the Thermosphere, temperature rises sharply, and auroras are seen. The International Space Station (ISS) orbits in the lower part of this layer.

Exosphere

The Exosphere is the outermost layer of the Earth's atmosphere. In this layer, the air is extremely thin, and the atmosphere gradually merges into outer space. Satellites orbit the Earth within this layer.