Variation law of air pressure at high altitude

Variation law of upper air pressure: There is a close relationship between atmospheric pressure and altitude, that is, atmospheric pressure decreases with altitude.

Near the sea level of 1 0,000 hectopascals, the air pressure drops 1 hectopascals with every increase in altitude of 10 m; In the vicinity of 500 hectopascals (5,500m), the air pressure drops 1 hectopascals for every 20m increase in height; In the vicinity of 200 hectopascals (1 2000m), the air pressure drops1hectopascals every 30m; It is used in aviation to determine the altitude of aircraft.

The altimeter on the plane converts the barometric height of the air barometer into height as the scale of the altimeter.

The International Civil Aviation Organization (ICAO) assumes that the dry air, air pressure and air temperature at the average sea level are 10 13.25hPa and 15℃ respectively, and the temperature below the tropopause is about 1 1km, which decreases by 6.5℃ per kilometer with the altitude drop rate. In this state, it is used as the reference standard of altimeter.

Causes of atmospheric pressure:

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.

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