Structure of Atmosphere - Indian Geography, UPSC IAS Exam Preparation Video Lecture | Geography (Prelims) by Valor Academy

The atmosphere is divided into several layers based on temperature changes. The structure of the atmosphere consists of the following layers: 1. Troposphere: This is the lowest layer of the atmosphere where weather phenomena occur. It extends from the Earth's surface up to an altitude of about 8-15 kilometers. 2. Stratosphere: Above the troposphere, the stratosphere extends up to an altitude of about 50 kilometers. It contains the ozone layer, which absorbs harmful ultraviolet radiation from the Sun. 3. Mesosphere: The mesosphere is located above the stratosphere and extends up to about 85 kilometers. Temperatures decrease with increasing altitude in this layer. 4. Thermosphere: The thermosphere is the layer above the mesosphere and extends up to about 600 kilometers. It is characterized by high temperatures due to the absorption of solar radiation. 5. Exosphere: The exosphere is the outermost layer of the atmosphere, extending beyond the thermosphere. It gradually merges with the vacuum of outer space.

The troposphere is the lowest layer of the atmosphere, extending from the Earth's surface up to an altitude of about 8-15 kilometers. It has the following characteristics: 1. Weather Phenomena: The troposphere is where weather phenomena occur, including clouds, precipitation, and atmospheric disturbances. 2. Temperature Decrease: Temperature decreases with increasing altitude in the troposphere at a rate of about 6.5 degrees Celsius per kilometer. 3. Air Density: The air density is the highest in the troposphere, with most of the atmospheric mass concentrated in this layer. 4. Composition: It mainly consists of nitrogen (78%) and oxygen (21%), along with traces of other gases such as carbon dioxide, water vapor, and argon. 5. Human Habitation: The troposphere is crucial for human habitation as it contains the oxygen we breathe and regulates the climate.

The ozone layer is a region within the stratosphere that contains a high concentration of ozone (O3) molecules. It plays a crucial role in the atmosphere due to the following significance: 1. UV Radiation Absorption: The ozone layer absorbs a significant amount of ultraviolet (UV) radiation from the Sun. It prevents most of the harmful UV-B and UV-C rays from reaching the Earth's surface, protecting living organisms from their damaging effects. 2. Skin Cancer Prevention: The ozone layer's ability to absorb UV-B rays helps in preventing skin cancer, cataracts, and other health issues caused by excessive exposure to UV radiation. 3. Climate Regulation: By absorbing solar radiation, the ozone layer influences the temperature distribution in the stratosphere and troposphere. It plays a role in regulating climate patterns and atmospheric circulation. 4. Environmental Protection: The presence of the ozone layer prevents the degradation of ecosystems, including the protection of phytoplankton in oceans, which are vital for the marine food chain. 5. International Cooperation: The depletion of the ozone layer led to international agreements like the Montreal Protocol, highlighting the significance of global cooperation in protecting the environment.

The mesosphere is the layer of the atmosphere located above the stratosphere and below the thermosphere. The temperature changes in the mesosphere as follows: 1. Decreasing Temperature: As altitude increases in the mesosphere, the temperature decreases. It is the coldest layer of the atmosphere, with temperatures dropping to as low as -90 degrees Celsius. 2. No Solar Heating: Unlike the stratosphere and thermosphere, the mesosphere does not receive direct solar heating. This absence of solar radiation contributes to the low temperatures in this layer. 3. Cooling by Infrared Radiation: The mesosphere cools primarily due to the emission of infrared radiation from carbon dioxide molecules present in this layer. 4. Mesopause: The mesopause is the boundary between the mesosphere and the thermosphere. It is the coldest part of the mesosphere, marking the transition to the higher temperatures of the thermosphere above. 5. Noctilucent Clouds: The mesosphere is known for the formation of noctilucent clouds, which are thin, bluish clouds that occur at high altitudes and are visible during summer nights in polar regions.

The thermosphere is a layer of the atmosphere located above the mesosphere and below the exosphere. It differs from other atmospheric layers in the following ways: 1. High Temperatures: The thermosphere is characterized by high temperatures. Despite the high temperatures, the thermosphere would not feel hot to humans due to the extremely low density of particles. 2. Solar Radiation Absorption: The thermosphere absorbs a significant amount of solar radiation, leading to increased temperatures. This is because the few particles present in this layer can absorb the intense solar energy. 3. Ionization: The high-energy solar radiation in the thermosphere causes the ionization of gas molecules, resulting in the formation of ions and free electrons. This ionization is responsible for the reflection and transmission of radio waves. 4. Aurora Borealis and Aurora Australis: The thermosphere is where auroras, such as the Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis), occur. These colorful displays are caused by the interaction between charged particles and the Earth's magnetic field. 5. Spacecraft Orbit: The thermosphere is where many satellites and spacecraft orbit the Earth. The low density of particles allows for easier movement and orbiting of objects in this layer.