Meteorological symbols in ink weather

It means atmospheric pressure. For ordinary people, just look at the PM value. The influence of atmospheric pressure on our life is subtle, not that it has no influence on us, but that its change is too small.

Air pressure 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. The famous experiment in the Madeborg hemisphere proved its existence. The international system unit of air pressure is Pascal, abbreviated as Pa, and the symbol is PA. A unit of air pressure, usually the height of a mercury column. For example, a standard atmospheric pressure is equal to the weight of a 760mm high mercury column, which is equivalent to bearing an atmospheric pressure of 1.0336kg in an area of one square centimeter. Because the weight and length units used in different countries are different, and the pressure units are not uniform, it is not convenient to compare and analyze the global pressure. Therefore, "hectopascals" are used as the air pressure unit in the world. According to the theory of molecular dynamics, the pressure of gas is caused by the frequent collision of a large number of molecules with the container wall. The impact time of a single molecule on the container wall is very short, and the effect is discontinuous, but a large number of molecules frequently collide with the container wall, and the force on the container wall is continuous and uniform. The ratio of this pressure to the wall area of the container is the pressure.