Pressure
The international unit of air pressure is Pascal (or Pa, symbol is Pa), refers to the gas on a certain point of the hydrostatic pressure, the source is the air in the air gravity, that is, per unit area of atmospheric pressure. In general meteorology, people use kPa (kPa), or use hPa (hPa) as a unit. The instrument that measures the pressure is called the barometer. The other commonly used units are: bar (bar, 1bar = 100,000 Pa) and the base of mercury column (or nominal mercury). The average pressure at sea level is about 101.325 kPa (76 cm mercury column), this value is also known as standard atmospheric pressure. In addition, in the chemical calculation, the international unit of air pressure is "atm". A standard atmospheric pressure is 1 atm. 1 standard atmospheric pressure equal to 101325 Pa, 1.01325 bar, or 76 cm mercury column. The regional difference in pressure is one of the direct causes of meteorological changes. Air pressure is an important variable in weather forecasting. ...