The relationship between air pressure and altitude

What is the relationship between altitude and air pressure

the relationship between air pressure and altitude

Elevation above sea level - in feet and meter - with barometric and atmospheric pressure - inches mercury, psia, kg/cm 2 and kPa. Jul 27, Atmospheric pressure drops as you go higher up in the atmosphere. Pressure at sea level is around a thousand millibars. Five kilometers. Pressure with Height. pressure decreases with increasing altitude. The pressure at any level in the atmosphere may be interpreted as the total weight of the air.

As the pressure increases it causes the container to crumple slightly, and returns to normal when the pressure decreases. A dial inside the container moves as it crumples and uncrumples. Using page 13 of the ESRT we can easily convert back and forth between inches of mercury and millibars. Air Pressure Constantly Changes Like all weather variables, air pressure is constantly changing. These changes are driven by changes in other factors such as altitude, temperature, and humidity.

It is therefore important for us to understand the relationship between air pressure and altitude, temperature, and humidity. Air Pressure and Altitude You may have seen or read about Mountain climbers like the one shown, needing to bring oxygen tanks with them as they climb higher and higher.

You may have also heard air at high altitudes referred to as being "thin". We know that air pressure is the weight of the air above us pressing down. So if we imagine climbing high into the mountains, as our altitude increases there is less air above us. If there is less air above us pressing down, the air pressure must decrease. As altitude increases, air pressure decreases. Air pressure and Temperature Cold air has high density causing it to sink down. This is why we say most clouds and weather are confined to the troposphere.

Change in the Atmosphere with Altitude

Layer in the atmosphere where the jet stream exists. Extends from 20 to 48 kilometers above the surface average location. Temperature increases with altitude because ozone gas molecules, present in this layer, absorb ultraviolet sunlight creating heat energy.

The layer of higher ozone concentrations, which reaches a maximum between 20 and 30 km above sea level, is also called the ozone layer.

Pressure Variation with Altitude in Earth's Atmosphere - Windows to the Universe

Ozone in the stratosphere protects life from harmful exposure to the sun's ultraviolet radiation. Even though we refer to an "ozone layer", keep in mind that ozone molecules account for a very small percentage of all air molecules in the stratosphere.

Even within the ozone layer, ozone is still a trace constituent. Density Air density can be defined as the number of air molecules per unit volume number density. Near sea level there are about 2.

Air molecules are held near the earth by gravity. In other words, air has weight. Weigh an empty bag, then fill it with air, it now weighs more. In addition gases, like air, are easily compressed, i. In other words, we say gases are compressible because they can easily be squeezed into a smaller volume. Solids and liquids on the other hand are not easily compressed. The weight of all of the air above a given point in the atmosphere squeezes air molecules closer together, which causes their numbers in a given volume to increase increase in number density.

The more air above a level and hence the more weight of air above a levelthe greater the squeezing effect or compression. Since air density is the number of air molecules in a given space volumeair density is typically greatest at the surface or sea level where it is squeezed by the weight of the entire atmosphere above and decreases as we move up in the atmosphere because the weight of air above becomes less and hence there is less of a squeezing effect See Figure Z.

  • Mapping Air Pressure
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Pressure Atmospheric air pressure results from the Earth's gravitational pull on the overlying air. Without gravity holding the atmosphere just above the ground surface, air molecules would spread out, and the gas pressure would be close to zero. The weight of the atmosphere acts as a force upon the underlying surface of the Earth. The amount of force excerted over an area of surface is called atmospheric pressure or air pressure.

the relationship between air pressure and altitude

Near sea level, the average air pressure is about In this class we will use the unit millibars mb to specify air pressure. At sea level the average air pressure is mb.

the relationship between air pressure and altitude

Another way to think of this is that the total weight of all the air above sea levels weighs enough to cause mb of air pressure. Since the air a gas is a fluid, the pressure force acts in all directions, not just downward.

Vertical Structure of the Atmosphere

The pressure force pushing downward due to the weight of the air is the same as the pressure force acting sideways and even upward. If you are having trouble understanding this, make an analogy with another fluid liquid water. Consider a deep swimming pool full of water. The water pressure anywhere in the pool depends on the weight of the water above that is the deeper you dive downward in the pool, the stronger the water pressure.

The pressure force is not just downward though, it pushes in on your body from all directions. The average air pressure at sea level mb or sometimes called one atmosphere of pressure is caused by the weight of all the air above sea level.

Pressure with Height: pressure decreases with increasing altitude

In the same way water pressure is caused by the weight of water above you. At a depth of 32 feet 9. Thus, the entire column of air from sea level to outer space weighs as much as a 32 foot column of water. Of course diving deeper than 32 feet downward into water means you will encouter an increasing water pressure enough to crush you if you go too deep. Typical change in air pressure with altitude.

Note how rapidly air pressure falls with increasing altitude. In the atmosphere, the air pressure at any point is caused by the weight per area of the air above that point. As we climb in elevation, fewer air molecules are above us less weight of air above us ; hence, atmospheric pressure always decreases as you move upward in the atmosphere See Figure B.

Another way to look at it is that the air pressure at any point in the atmosphere is exactly enough to support the weight of the column of air above it. A balance exists between the gravitational force pushing air downward and the upward directed pressure force. This balance is called hydrostatic balance see figure.

Earlier we made an analogy between diving down in water and moving downward in the atmosphere.