What does the weatherman mean by "hectopascals", such as 800 hectopascals and 700 hectopascals?

Is the unit of air pressure, which is the atmospheric pressure acting on the unit area, that is, it is numerically equal to the gravity of the vertical air column extending upward to the upper limit of the atmosphere on the unit area. Air pressure varies not only with height, but also with temperature. The change of air pressure is closely related to the change of weather.

Abbreviation for atmospheric pressure. Is the atmospheric pressure exerted per unit area, which is equal to the weight of the vertical air column extending upward to the upper limit of the air per unit area. Air pressure depends on altitude, temperature and so on. It generally decreases with the increase of height. In the horizontal direction, the difference of atmospheric pressure leads to air flow. A unit of air pressure, usually used to indicate the height of a mercury column.

Extended data:

The average pressure at sea level is about 10 1.325 kPa (equivalent to 76 cm Hg), also called standard atmospheric pressure. Moreover, in chemical calculation, the international unit of pressure is ATM. The standard atmospheric pressure is one atmosphere. The standard atmospheric pressure is equal to 10 1325 Pa, 1.0 1325 Bar, or 76 cm Hg.

The regional difference of atmospheric pressure is one of the direct causes of meteorological changes. Air pressure is an important variable in weather forecast. On the earth, the source is the gravity of air in the atmosphere, and the normal air pressure is 1 kg/cm2.

The atmosphere above is thin, and the air there is less attractive than that in the lower layer, so the air pressure in the upper layer is lower than that in the lower layer. For example, the air pressure in high mountains is lower than the sea level.

People's use of air pressure refers to the use of compressed gas to transfer energy to do work, and the use of air pressure as power. Simply put, compressed air makes the pressure cylinder and the pressure motor become power sources through air pressure.

Baidu encyclopedia-air pressure