Britannica Sources used in this answer

How did the mercury barometer and thermometer advance meteorology?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Weather forecasting Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.

The scientific study of meteorology was significantly advanced by the invention of the mercury barometer and the development of the thermometer in the 17th century. Before these instruments, meteorology lacked the objective, quantitative data necessary for rigorous scientific analysis.1

The mercury barometer, invented by Evangelista Torricelli around 1643–44, provided the first reliable means to measure atmospheric pressure. By observing that the height of the mercury column varied, scientists were able to quantify changes in the atmosphere's weight, a fundamental component of weather patterns. Subsequent experiments by Blaise Pascal further demonstrated that air pressure decreases with altitude, providing critical insights into the vertical structure of the atmosphere.123

Concurrent advancements in thermometer technology allowed for the precise measurement of temperature. Together, these tools enabled 17th- and 18th-century scientists to formulate essential physical laws regarding gas pressure, density, and temperature. This transition from subjective observation to empirical measurement laid the foundation for modern weather forecasting, eventually leading to the development of synoptic meteorology and numerical weather prediction models.14