Meteorology The Atmosphere

Composition of the Atmosphere The atmosphere is made up of a layer of gases. A more common word for atmosphere is air. The atmosphere extends from the surface of the earth until you reach space. The atmosphere is composed of 3 main gases and various trace elements. Nitrogen is the most abundant gas at 78%. Oxygen makes up only 21% of the atmosphere while Argon completes the remaining 1%.

In addition to these gases, there are 2 abundant compounds In addition to these gases, there are 2 abundant compounds. Water Vapor, H2O vapor, is added to the atmosphere through the process of evaporation and is removed through condensation and precipitation. This process is more commonly referred to as the water cycle. Carbon Dioxide, CO2, can be added through volcanic eruptions and human activities.

Layers of the Atmosphere The earth’s atmosphere is broken down into layers based on how the temperature changes. This change results from how solar energy is absorbed in the atmosphere.

Temperature Change with Altitude

The first layer of the atmosphere is called the troposphere The first layer of the atmosphere is called the troposphere. In this layer, all of the earth’s weather occurs and you will find almost all of the water vapor and carbon dioxide. As the altitude increases the temperature decreases because almost all of the atmospheric heating occurs from the earth’s surface as heat is re- radiated. The troposphere extends to an altitude of 12 km.

The second layer of the atmosphere is called the stratosphere The second layer of the atmosphere is called the stratosphere. In this layer, you will find the ozone layer which protects us from UV radiation. As the altitude increases the temperature increases because the ozone layer is absorbing ultraviolet radiation. The stratosphere extends from 12 km to 50 km.

The third layer of the atmosphere is called the mesosphere The third layer of the atmosphere is called the mesosphere. In this layer, you will find the coldest temperatures. As altitude increases the temperature decreases. The mesosphere extends from 50 km to 80 km.

The last layer of the atmosphere is called the thermosphere. In the lower area of this layer, you will find an area called the ionosphere. In this area, loose ions and free electrons interact with solar radiation causing the auroras. The upper area of the thermosphere is called the exosphere. This layer simply blends away (fades) into space. The temperature increases as the altitude increases (we think). Scientists cannot get an accurate temperature reading in the thermosphere because there are not enough molecules to strike the thermometer.