Earth’s Atmosphere: Composition, Layers, and Phenomena
Atmosphere: Composition and Structure
The Earth’s atmosphere is primarily composed of nitrogen (78.88%) and oxygen (20.95%).
Troposphere
In the troposphere, the density gradient decreases with elevation. Approximately 50% of the atmospheric mass is found below 5.5 km, and 75% is below 11 km. The temperature decreases by an average of 6°C per kilometer of elevation.
Atmospheric nitrogen is recycled through human activities and microbial action on animal waste. Oxygen is mainly recycled through respiration by animals and plants via photosynthesis. Carbon dioxide is also recycled through respiration and photosynthesis, but in the opposite direction to oxygen.
Ozone is formed when solar radiation splits oxygen molecules into individual atoms, which then bind to diatomic oxygen molecules.
Atmospheric Layers
Chemically, the atmosphere is divided into:
- Homosphere: The first 100 km, with a constant ratio of components.
- Heterosphere: Up to 900 km, with a predominance of light gases.
- Exosphere: Where light particles escape into space.
Physically, the atmosphere is divided into thermal layers:
- Troposphere: The lowest layer, characterized by variable weather conditions and cloud formation.
Clouds
Clouds are classified by altitude:
- Low clouds: up to 2500 m
- Middle clouds: 2500 to 6000 m
- High clouds: above 6000 m
Clouds can be composed of water or ice. Gray clouds indicate water condensation, while clouds with water vapor below freezing point can lead to hail. Morphologically, clouds are classified as stratus, nimbus, cumulus, and cirrus.
Stratosphere
Above the troposphere lies the stratosphere, around 10 km in altitude. This region contains jet streams and the intertropical convergence zone, which influences rainfall and climate. The ozone layer, crucial for life on Earth, is located in the stratosphere, peaking around 30 km. The stratopause, a heated region, ends at approximately 50 km altitude.
Colombia’s bimodal climate is controlled by the intertropical convergence zone, an area where northeast and southeast trade winds converge.
Mesosphere
Above the stratosphere is the mesosphere, where temperatures drop to -80°C, ending at the mesopause at 80 km altitude. Radio waves are reflected at night above the mesopause and during the day below it. The mesopause exhibits a sharp temperature contrast, even though the air density is about one millionth of g/cm3.
Thermosphere (Ionosphere)
The thermosphere, also known as the ionosphere, is characterized by hot and rarefied layers. Polar auroras occur in this region.
Exosphere and Beyond
Satellites orbit at various altitudes:
- 200 km: Satellites for geological, military, and crop assessment.
- 900 km: Satellites for observing outer space.
- 35000 km: Meteorological observation satellites for panoramic views.
Beyond 900 km, in the exosphere, research is conducted on new materials and biotechnology. The magnetosphere, containing the Van Allen belts, is reached by cosmic rays in the exosphere. Solar wind pressure deforms the Earth’s magnetic field, causing dynamic variations. During solar magnetic storms, associated with sunspot cycles, the Earth’s magnetic field intensity fluctuates, interfering with magnetometer surveys.
Terrestrial magnetism is important for navigation, mineral resource exploration, and irrigation system management, contributing to food safety plans.