Although meteorologists now have at their fingertips a wide array of sophisticated meteorological technology, the barometer, psychrometer, anemometer and thermometer are still used.
The barometer is an instrument used to measure air pressure. There are two types of barometers: the mercurial barometer, and the aneroid barometer. An aneroid barometer is probably the type that you have in your home. It contains no liquid, and works through the use of an aneroid cell that runs on a lever system.
The barograph is a recording aneroid barometer that graphs out, using pen and paper attached to a rotating cylinder, air pressure readings over time. They are commonly used at observatories and weather stations.
The mercurial barometer was invented by Evangelista Torricelli in 1643. Mercury inside a glass tube rises and falls indicating changes in air pressure. This type of barometer is more commonly seen in a physics laboratory. It can maintain air pressure data for use in precise experiments.
Sling psychrometers are used to measure water vapor in the atmosphere, a condition that meteorologists call relative humidity. The sling psychrometer is made up of two thermometers mounted next to one another on a strip of aluminum, with an attached wooden handle.
The thermometer on one bulb is left uncovered, while the second thermometer's bulb is covered with a wet wick resembling a shoelace. The meteorologist then grabs the handle of the psychrometer and spins it around for several minutes. While the psychrometer is spinning, water will evaporate from the covered wick, unless the air is 100% saturated.
If the temperatures of the wet bulb and the dry bulb are the same, then the air is considered totally saturated or has a relative humidity level of 100%. In all other circumstances, the wet bulb will be at a lower temperature than the dry bulb. Meteorologists then refer to a chart that gives them the relative humidity.
An anemometer is an instrument used to measure wind speed. Three open cups are attached to a vertical shaft connected to a wind recorder. The force of the wind causes the cups to rotate and wind speed is determined by how fast the cups are spinning. The faster the cups spin, the greater the wind speed.
The best anemometer readings are taken when the instrument is placed on a tall object, such as a roof where, the wind blows freely.
The thermometer is used to measure air temperature. It consists of a glass bulb filled with mercury or alcohol. The material inside the bulb expands when temperatures are warmer and contracts when temperatures are cool.
