Barometers and thermometers. How do meteorologists monitor the weather?

Everyone knows that meteorologists use a barometer and a thermometer; less familiar to non-specialists other instruments, which equipped with modern meteorological stations. Let what is said below serve as a kind of guide for a meteorologist-fan in case he wants to not only observe the clouds, but wants to arrange a small meteorological station at his home.

The barometer measures not only the air pressure, but also its changes, due to the fact that for different types of weather, air has a different weight. As air penetrates into any room, external pressure can be measured simply at home, in your room. The meteorologist also registers the air pressure inside the meteorological station, using for this purpose our grandfathers still in use, but at the same time a very reliable mercury barometer.

In this device, the air balances a column of mercury placed in a tightly sealed tube from above; the height of the column characterizes the value of the air pressure. Barometers, which are usually sold in stores, consist of a metal box, from which air is pumped out; The pressure change with the aid of the levers is transmitted to the arrow moving in a circle with the divisions. With the same weather, the air pressure at the meteorological station, located at an altitude of 800 meters above sea level, is less than at a station lying, for example, at an altitude of 200 meters. Therefore, in order to be able to compare the results of observations at different stations, meteorologists have to bring the air pressure at this station to the pressure at sea level.
 

To measure the temperature near the meteorological station, there is always a small box with shutter-walls, freely flowing air. In this booth at an altitude of two meters above the ground are installed various instruments, reliably protected from rain. If someone wants to set the temperature "in the sun", hang his thermometer in the sun, tell him that it's pointless - so he learns only the temperature of the heated wall of the house. The actual air temperature should be measured only in the shade. Therefore, if you do not have a meteorological booth, hang the thermometer as far as possible freely on the north side of your house so that the rays of the sun do not fall on it. In the meteorological box, among other things, extremal temperatures are measured, that is, the highest and the lowest during the day.

In addition to the barometer and thermometer, the "arming" of the meteorological station always has a barograph and a thermograph - instruments that independently record all changes on a rotating drum; Thus, a clear picture of the progress of air pressure and temperature, for example, over a week, is obtained.

Two other devices are installed not far from the meteorological booth. This rain gauge is a metal cylinder of a certain diameter, by which the amount of precipitation deposited during a day is measured, and the heliograph is usually a glass ball playing the role of a lens; collected in focus rays burn paper tape; along the length of the burnt areas, you can determine the duration of sunshine per day.