What it Means when a Barometer is Rising or Falling

Long before mankind developed sophisticated technology like satellites to forecast the weather, people had to depend on simpler methods such as the barometer. This instrument detects and measures changes in the atmosphere that vary when the weather is about to change. These measurable changes can help people to prepare for weather events that affect their daily lives.

The Invention of the Barometer

The first barometer was invented in the 1600’s by Evanglista Torricelli, a pupil of Gallileo.  Torrecelli was an early scientist who used mercury to demonstrate that air had weight and could push up mercury in a glass column. He also noticed that the height of the mercury varied slightly from day to day. He concluded that this was because of changes of pressure in the atmosphere. He then noticed that this rising and falling of the mercury column corresponded to changes in the weather. This concept has been improved upon over time, but the fundamental concept has remained the same.

How Barometers Work

The glass column filled with mercury, though a functioning scientific instrument for measuring pressure changes in the atmosphere was fragile and unwieldy, nor was it then known that mercury was a toxic substance. In the 1840’s, Lucien Vidie, a French inventor, developed a new kind of barometer. The “aneroid” barometer exchanged the liquid with a sensitive capsule made of thin, copper-beryllium alloy. Changes in the thickness of this thin, alloy material are transferred to a needle that on a graduated disks that display the changes in pressure. This was further improved in more modern times with thin, metallic strips with an electric current run across them. As the strips move further apart, the distance is measured in current on capacitors that transfer the information onto a digital display.

Further reading – How and what does a barometer measure

When Barometric Pressure Is Rising

When the mercury in the glass tube in the barometer rises, it indicate that the atmospheric pressure is rising. This effect signals that fair weather is likely, because high pressure systems act as a barrier to approaching systems, diverting their course. When barometric pressure is rising, you can count on clear weather for your picnic or boating excursion.

When Barometric Pressure Is Falling

When the mercury in the glass tube of the barometer falls, pressure is low in the atmosphere. Stormy weather conditions choose the path of least resistance and move into the area, so that if you see the pressure indicator of the barometer falling, you may wish to change your outdoor plans or bring an umbrella.