1 standard atmospheric pressure =760mm mercury (Hg) column height.

Is the atmospheric pressure acting on the unit area, which is equal to the weight of the vertical air column extending upward to the upper limit of the atmosphere on the unit area. The air pressure is related to altitude, temperature and other conditions. It generally decreases with the increase of height. In the horizontal direction, the difference of atmospheric pressure causes the flow of air. A unit of air pressure, usually the height of mercury column.

Extended data:

influencing factor

The pressure is related to altitude, atmospheric temperature and atmospheric density, and generally decreases exponentially with altitude.

The air pressure varies daily and annually. In a year, the air pressure is higher in winter than in summer. In a day, the air pressure has a maximum value and a minimum value, which appear at 9 ~10 and15 ~16 respectively, and a second-highest value and a second-lowest value, which appear at 2122 and 3 ~ 4 respectively. The daily variation of air pressure is small, generally 0.1~ 0.4 kPa, and decreases with the increase of latitude.

The change of air pressure is closely related to wind and weather, so it is an important meteorological factor. The commonly used air pressure units are Pa, mm·Hg and mb.

The conversion relationship between them is:100pa = 1 millibar ≈3/4 mm mercury column height. Commonly used instruments for measuring atmospheric pressure in meteorological observation include mercury barometer, empty box barometer and barometer. When the temperature is 0℃, the pressure of 760mm vertical mercury column, the standard atmospheric pressure was first measured by Italian scientist Torricelli.

Baidu encyclopedia-atmospheric pressure