Understanding barometric pressure


The air around us has a weight which presses against everything it touches, from every direction. In terms of names, this can be called in many different ways, such as atmospheric or barometric pressure. Moreover, when you hear people talking about air pressure, this is what they are referring to.

It’s defined as the force exerted on a surface by the air above it as gravity pulls it towards Earth. The pressure is usually measured with a barometer which contains a column of mercury in a glass tube.

This column either rises or falls as the weight of the atmosphere changes. Scientists and meteorologists describe the atmospheric pressure by how high the mercury rises.

The unit measure is an atmosphere (atm) which is equal to the average air pressure at sea level at a temperature of 59 degrees Fahrenheit. One atmosphere equals 1,013 millibars or 29.92 inches of mercury, this being the reference point.

As altitude increases, the atmospheric pressure drops, which leads to differences we can perceive. Just to give an example, the atmospheric pressure on Denali, Alaska, is about half that of Honolulu, Hawaii. Honolulu is a city at sea level, while Denali is the highest peak in North America.

Airplane travel

If you’ve traveled by airplane, you probably have experienced pressure in your ears, popping or even severe pain sometimes. This happens because an airplane lifts extremely fast into the air and the pressure in the inner ear and the air pressure outside don’t have time to equalize.

The result is that the tympanic membrane or eardrum swells outward. If you picture a loaf of bread rising while baking, you’ll get the idea.

Solutions include swallowing more often, chewing gum, yawning or the Valsalva maneuver which entails holding a mouthful of air and a pinched nose while you gently force air out until your ears pop. However, this is not recommended if you are sick with a cold or allergies.


Lower oxygen levels

As the pressure subsides, so does the amount of oxygen available to breathe. At very high altitudes, both the atmospheric pressure and the available oxygen get so low that there’s a significant risk for people to get sick or even die.

Professional mountain climbers use bottled oxygen when they ascend very high peaks. They also take the time to get used to the altitude. A fast transition from higher pressure to lower pressure can cause decompression sickness.

The same problem goes for scuba divers. If they come to the surface too quickly, there’s not enough time to adapt to the change in pressure and this might lead to sickness.

Atmospheric pressure is also an indicator of weather. A low-pressure indicator usually means that there will be cloudiness, wind, and precipitation, while a high-pressure one indicates a fair and calm weather.


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