Atmosphere of Earth
Atmosphere of Earth
An atmosphere is a layer of gas or layers of gases that envelope a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases.
The composition of the Earth’s atmosphere changes with the altitude. The major constituents of the Earth’s atmosphere are;
- Nitrogen – 78.09%
- Oxygen – 20.95%
- Argon – 0.93%
- Carbon Dioxide – 0.039% (remaining other gasses)
The pressure exerted by the weight of air at a given point is known as "“"Atmospheric Pressure" or "Barometric Pressure."
With increasing altitude, the atmospheric pressure decreases.
On an average, a column of air (which is normally one square centimeter in cross-section), measured at the sea level, has the weight of about 1.03 kg (about 10.1 N).
The Average Air Pressure is about 14.70 pounds per square inch, (equivalent to 1,013.25 × 103 dynes per square centimeter or 1,013.25 millibars) at the sea level.
A visible mass of condensed vapor floating above the general level of the ground is known as Cloud.
Based on the altitude, cloud is classified as;
- High Altitude Cloud: For example, Cirrus, Cirrocumulus, & Cirrostratus.
- Middle Altitude Cloud: For example, Altostratus and Altocumulus.
- Low Altitude Cloud: Stratus, Stratocumulus, Cumulus, and Nimbostratus (it can be also seen in the middle altitude).
- Vertical: Cumulonimbus