Last week we experienced an unusual change in air pressure. According to the meteorologists, the variation in atmospheric pressure was unique in its extend. Within 24 hours, the pressure fell from 1044 hPa down to 990 hPa, a rare fall of more than 50 hPa.
I have an old barometer that I purchased, I believe, in Best (Home Furnishing) while living in North Carolina. It is combined with a thermometer and hygrometer as well, the last measuring the humidity of the air. I could clearly follow the fall in pressure as the indicator on the middle dial kept moving from fair to stormy.
I find it quite intriguing that the air which surrounds us and feels light and weightless actually has a certain mass. The force of the weight that it displays upon a certain area is what is called the air pressure. The air can also be compressed, that is the tiny particles, or molecules of various gases take up less room and thus the pressure elevates, or vice-versa.
The standard atmosphere (symbol: atm) is a unit of pressure and is defined as being equal to 101,325 Pa or 101.325 kPa, which corresponds to the weight of 14.696 lbs/sq2 (1.0333 kg/cm2) and is the average air pressure at sea level. This means hundreds of pounds of pressure are pressing at us from all sides and at all times. We are able to survive this pressure because the air in our bodies is under the same pressure as outside us. However, it can happen that the air around us can change suddenly and our bodies might not follow, such as when we ascent or descend in a plane. This is why we feel our ear pop, as our bodies try to equalize the difference.
Air pressure can also help us forecast the weather as well. If a high pressure system is on its way, this means cooler temperatures and clear skies. If a low pressure system is coming, the weather will be warmer, accompanied by storms and rain. Which is exactly what happened with our weather last week; we went from beautiful sunny day to a dreadful winter storm just within a course of twenty four hours.