Earth's Atmosphere: Layers and Composition

• Earth's atmosphere is a complex, dynamic, natural gaseous envelope that supports life.
• The atmosphere primarily consists of nitrogen and oxygen, along with smaller amounts of argon, carbon dioxide, neon, and trace gases.
• It protects life by absorbing harmful UV radiation, moderating temperature extremes, and facilitating water and nutrient cycles.

Atmospheric Layers

• The atmosphere is divided into layers based on temperature, chemical composition, density, and movement.
• The main layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Troposphere

• The troposphere is the lowest layer, extending from the surface to 8-14.5 kilometers (5-9 miles).
• It contains about 75% of the atmosphere's mass and almost all water vapor and aerosols.
• Temperature decreases with altitude at an average rate of 6.5°C per kilometer (environmental lapse rate).
• Most weather phenomena occur in the troposphere.
• The tropopause is its upper boundary, separating it from the stratosphere.

Stratosphere

• The stratosphere extends from the tropopause to about 50 kilometers (31 miles).
• Temperature increases with altitude due to UV radiation absorption by the ozone layer.
• The ozone layer absorbs harmful UV radiation, protecting life.
• Air in the stratosphere is stable and dry with minimal vertical mixing.
• The stratopause marks the upper boundary of the stratosphere.

Mesosphere

• The mesosphere extends from the stratopause to about 85 kilometers (53 miles).
• Temperature decreases with altitude, making it the coldest layer.
• Meteors burn up in the mesosphere.
• The mesopause is the coldest point in the atmosphere and the upper boundary of the mesosphere.

Thermosphere

• The thermosphere extends from the mesopause to 500-1,000 kilometers (311-621 miles).
• Temperature increases with altitude due to the absorption of high-energy solar radiation.
• It is characterized by high temperatures but low density.
• The International Space Station orbits in the thermosphere.
• Auroras occur in the thermosphere due to interactions between charged particles and Earth's magnetic field.
• The ionosphere, containing ions and free electrons, is located within the thermosphere and exosphere and is important for radio wave propagation.

Exosphere

• The exosphere is the outermost layer, extending from the thermosphere to space.
• Atmospheric gases gradually escape into space.
• The exosphere lacks a clear upper boundary.
• It mainly consists of low densities of hydrogen and helium.

Key Atmospheric Properties

• Atmospheric pressure is the force exerted by the weight of the air above a point.
• Pressure decreases with altitude.
• Temperature measures the average kinetic energy of air molecules.
• Temperature varies with altitude and solar radiation.
• Humidity is the amount of water vapor in the air.
• It affects cloud formation, precipitation, and weather patterns.
• Density is the mass of air molecules per unit volume.
• Density decreases with altitude.
• Composition refers to the types and amounts of gases in the atmosphere.
• The composition is relatively constant in the lower atmosphere but varies in the upper atmosphere.

Atmospheric Circulation

• Global wind patterns are driven by differences in air pressure and temperature.
• The Coriolis effect deflects winds due to Earth's rotation: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
• Jet streams are fast-flowing air currents in the upper troposphere and lower stratosphere.
• They influence weather patterns and air travel.

Atmospheric Phenomena

• Clouds are formed by the condensation of water vapor.
• Precipitation includes rain, snow, sleet, and hail.
• Storms are atmospheric disturbances characterized by strong winds, heavy precipitation, and lightning.
• Optical phenomena include rainbows, halos, and mirages caused by light interaction with atmospheric particles.

Explore Earth's atmosphere: a life-supporting gaseous envelope. Learn about its composition of nitrogen, oxygen, argon, and trace gases. Discover the distinct atmospheric layers—troposphere, stratosphere, mesosphere, thermosphere, and exosphere—and their unique characteristics.