The Atmosphere

Layers of the Atmosphere Vertical temperature (T) profile The structure of the atmosphere is based on the temperature changes. 1.Troposphere 2.Stratosphere 3.Mesosphere 4.Thermosphere 5.Exosphere

The Troposphere Lower part of the atmosphere Energy source is heating of the earth’s surface by the sun. Temperature generally decreases with height all the way up to about 11 km The height varies varies from about 8 km (poles in winter) to about 20 km (tropics) Weather and climate layer. Air circulations (weather) take place mainly here. It includes most of atmosphere’s mass.

The Stratosphere stratosphere troposphere Sun’s ultraviolet light is absorbed by ozone, heating the air. Heating causes increase of temperature with height. Boundary between troposphere and stratosphere is the tropopause. Stratosphere goes from about 10 to 50 km above the surface. stratosphere troposphere

The Mesosphere Above the Stratosphere, 50-90 km from the ground. Very little ozone, so no solar heating The mass of atmosphere is only 0.1% of the total, and the density is too low. Air continues to cool with height in mesosphere

The Thermosphere (= The Ionosphere) Above 90 km, residual atmospheric molecules absorb solar wind of nuclear particles, x-rays and gamma rays. Absorbed energy causes increase of temperature with height. Air molecules are moving fast, but the pressure is very low at these heights.

Importance of Stratosphere, Mesosphere and Thermosphere Solar nuclear particles, x- rays, gamma rays, and ultraviolet light can damage living cells. Thermosphere, mesosphere and stratosphere shield life on Earth from these damaging rays.

Characterizing the Atmosphere Based on Electrical Properties The ionosphere is an atmospheric layer located from the upper mesosphere into the thermosphere The ionosphere contains electrically charged particles called ions due to UV radiation The ionosphere affects AM radio waves, absorbing them in the day and reflecting them at night The ionosphere creates the northern lights (aurora borealis) and the southern lights (aurora australis) through interactions between the sun’s rays and earth’s magnetic field

The Exosphere It is the outermost layer. Not much is known about this layer.