What is the atmospheric pressure?

In physics, the annual average atmospheric pressure at sea level with latitude of 45 degrees (that is, the altitude is zero) is defined as 1 standard atmospheric pressure (atm). This standard atmospheric pressure is a definite value. The value is 1 standard atmospheric pressure = 760mmhg = 1.0 133 engineering atmospheric pressure =1.0133x105pa = 0.10.

Due to gravity, near the surface of the earth, the gravity of the earth is large, the molecular density of air is high, and the frequency of hitting the surface of the object is high, resulting in high atmospheric pressure. Away from the surface of the earth, the gravity of the earth is small, the molecular density of air is low, and the frequency of hitting the surface of the object is low, so the atmospheric pressure is small.

So the air pressure at different heights on the earth is different, and the higher the position, the smaller the air pressure. In addition, the temperature and humidity of the air also affect the atmospheric pressure.

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Reason:

Atmospheric pressure is the result of the earth's gravity. Due to the gravity of the earth, the atmosphere is "sucked" to the earth, producing pressure, and the atmospheric pressure near the ground is the highest. Atmospheric pressure in meteorological science refers to the weight of atmospheric column per unit area (atmospheric pressure), that is, the pressure exerted by atmospheric column per unit area.

There are two units of air pressure: millimeter (mm) and millibar: the unit of air pressure expressed by the height of mercury column. For example, the air pressure is 760 mm, which means that the atmospheric pressure at that time is equal to the pressure generated by a mercury column with a height of 760 mm, and the other is millibar (mb) which is often heard in weather forecast broadcasts.

It is a unit of air pressure expressed by the pressure of atmospheric pressure column per unit area. 1 millibar = 1000 dynes/cm2 (1 bar = 1000 millibar). Therefore, 1 millibar means that 1000 dynes are applied to an area of 1 cm2. When the air pressure is 760mmhg, it is equivalent to 10 13.25mbar, which is called a standard atmospheric pressure.

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