Relationship of air pressure and altitude

Change in the Atmosphere with Altitude | UCAR Center for Science Education

relationship of air pressure and altitude

Altitude air pressure calculator. is charity-funded and written by independent doctors. Elevation above sea level - in feet and meter - with barometric and atmospheric pressure - inches mercury, psia, kg/cm 2 and kPa. Altitude is calculated from air pressure and vice versa. The following table and graph illustrate the relationship between altitude and pressure using the default.

Physical performance is affected at altitudes over feet metres the higher the altitude, the more impaired the physical performance of the body.

relationship of air pressure and altitude

Physical or work performance is related to oxygen consumption, which decreases at high altitudes, due to less oxygen in a given volume of air. Endurance capacity is commonly measured by a reduction of 3 to 3. If a person remains at high altitudes for long periods, they begin to acclimatise. At 9, feet it can take 7 to 10 days to acclimatise.

relationship of air pressure and altitude

At higher altitudes it can take longer. A minority of people will never acclimatise. Therefore, this is the reason that changes in air pressure can have the effect of causing a popping in the ears. This can occur when flying in a plane or driving up into the mountains; in any situation where the atmospheric pressure is raised.

In general, the air in body cavities is normally of equal pressure to the air outside of the body. However, if the atmospheric pressure changes quickly, or if there is any blockage between the outside of the body and the internal cavities, "equalising" of pressure might not occur properly.

Barometric formula - Wikipedia

A tangible example of how you may have experienced this is when you take a drink bottle on a flight. If you open an empty plastic bottle while you are in the air, then tightly close it, when you land, you will find the increase in air pressure has caused the air in the bottle to compress, as if it has been sucked out with a vacuum, and the bottle will have collapsed inwards.

As the pressure decreases, the air spaces will expand.

relationship of air pressure and altitude

This shows that when you multiply the surrounding pressure of a gas, by the volume of the gas, you will always have the same number. So if the amount of pressure is increased, the volume of gas must decrease, and vice versa. To avoid injury, the diver will need to equalise the pressure in their air spaces with the surrounding pressure. While they are diving, care must be taken to continue breathing — if a diver holds their breath and ascends to an area where less pressure is exerted, the air trapped in the lungs will expand and can stretch the lungs which can lead to injury.

These air spaces can become overfull, so the diver will need to equalise, and breath out any excess air. Failure to do so can cause the eardrum and lungs to burst. The buoyancy compensator BCD will also expand due to decreased pressure, so the diver will need to release air from the BCD to control their ascent. Because it is difficult for tropospheric air to rise into the tropopause region, clouds are typically confined below the tropopause region See Figure Ysince clouds form in air moving vertically upward.

This is why we say most clouds and weather are confined to the troposphere. 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.

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.

Vertical Structure of the Atmosphere

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.

relationship of air pressure and altitude

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.

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.

relationship of 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. 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.

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. 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.