Vertical Structure of the Atmosphere

Vertical Structure of the Atmosphere

Part 2

Principle

The changes in the atmosphere with height are results of specific physical conditions which exist on the earth and in its atmosphere. The vertical changes in temperature are important in constraining weather events to the lowest 10-12 km of the atmosphere. The ozone layer, located near 25 km above the earth's surface, causes the temperature to rapidly change in the middle atmosphere.

Figure 2 - Relationship Between Pressure and Height in the Atmosphere

Changes in Air Pressure with Height

Pressure always decreases with height and does so most rapidly near the ground. Why do sealed balloons increase in volume when they rise in the atmosphere? Why do your ears "pop" when you ride on an elevator in a tall building or when you take off in an airplane?
As we move upward in the atmosphere, the weight of the air upon us should decrease because there is less air above us. Thus, air pressure decreases with increasing height.

Pressure decreases with height more rapidly near the ground because the atmosphere is a gas which can compress in its response to the earth's gravitation effect.

If more air is packed into the same length vertical column, then the air column will weigh more and, hence, the air pressure will be greater.
So we may have horizontal variations of pressure if two air columns are next to one another, both of the same height but one with more molecules packed into it than the other. This is how we get high and low pressure systems.

The rate at which air pressure changes with height is determined primarily by the average temperature in the column under consideration.
In colder regions, atmospheric pressure decreases more rapidly with height than normal or than is observed in warmer areas.

Changes in Air Temperature with Height

Temperature has a more complicated structure, mostly because the temperature of the air relies on the energy its molecules receive from radiation.
The two main sources of radiation in the atmosphere are the sun and the earth. The sun's radiation is mostly near infrared (37%), visible (44%), and ultraviolet (7%) while the earth's radiation is mostly far infrared. Infrared is generally what we feel as "heat", visible is what we see, and ultraviolet is what our skin absorbs to make us tan or burn. The temperature structure of the atmosphere is controlled significantly by whichever of these three types of radiation are affecting the region.

Temperature generally decreases with height in the lowest 10 km or so above the earth's surface.
This 'layer' is called the troposphere. How can we tell temperature decreases with height? Do mountains give us a clue?

Temperature increases with height from about 10 km to 50 km above the earth's surface.
This layer is called the stratosphere and results from absorption of solar radiation by ozone. How can we "see" the change from the troposphere to the stratosphere? The tops of large thunderstorm clouds can show us.

Temperature again decreases and increases with height above the stratosphere.
These layers are called the mesosphere and thermosphere, respectively.

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	Vertical Structure of the Atmosphere Part 2

	Principle	The changes in the atmosphere with height are results of specific physical conditions which exist on the earth and in its atmosphere. The vertical changes in temperature are important in constraining weather events to the lowest 10-12 km of the atmosphere. The ozone layer, located near 25 km above the earth's surface, causes the temperature to rapidly change in the middle atmosphere.

	Figure 2 - Relationship Between Pressure and Height in the Atmosphere

	Changes in Air Pressure with Height	Pressure always decreases with height and does so most rapidly near the ground. Why do sealed balloons increase in volume when they rise in the atmosphere? Why do your ears "pop" when you ride on an elevator in a tall building or when you take off in an airplane? As we move upward in the atmosphere, the weight of the air upon us should decrease because there is less air above us. Thus, air pressure decreases with increasing height. Pressure decreases with height more rapidly near the ground because the atmosphere is a gas which can compress in its response to the earth's gravitation effect. If more air is packed into the same length vertical column, then the air column will weigh more and, hence, the air pressure will be greater. So we may have horizontal variations of pressure if two air columns are next to one another, both of the same height but one with more molecules packed into it than the other. This is how we get high and low pressure systems. The rate at which air pressure changes with height is determined primarily by the average temperature in the column under consideration. In colder regions, atmospheric pressure decreases more rapidly with height than normal or than is observed in warmer areas.

	Changes in Air Temperature with Height	Temperature has a more complicated structure, mostly because the temperature of the air relies on the energy its molecules receive from radiation. The two main sources of radiation in the atmosphere are the sun and the earth. The sun's radiation is mostly near infrared (37%), visible (44%), and ultraviolet (7%) while the earth's radiation is mostly far infrared. Infrared is generally what we feel as "heat", visible is what we see, and ultraviolet is what our skin absorbs to make us tan or burn. The temperature structure of the atmosphere is controlled significantly by whichever of these three types of radiation are affecting the region. Temperature generally decreases with height in the lowest 10 km or so above the earth's surface. This 'layer' is called the troposphere. How can we tell temperature decreases with height? Do mountains give us a clue? Temperature increases with height from about 10 km to 50 km above the earth's surface. This layer is called the stratosphere and results from absorption of solar radiation by ozone. How can we "see" the change from the troposphere to the stratosphere? The tops of large thunderstorm clouds can show us. Temperature again decreases and increases with height above the stratosphere. These layers are called the mesosphere and thermosphere, respectively.

	Back to Part 1