On Agrometeorology

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The unit of air pressure is summarized by the mercury column pressure per unit area. In physics, the unit of pressure is "bar": a force of one dyne per square centimeter is called bar. Meteorologically speaking, this unit is too small. Take 1 0,000,000 dynes/cm2 as 1 bar, and take one thousandth of a bar as the air pressure unit, which is called 1 millibar. Millibar is one thousandth of a bar, which is equal to the pressure of 0.76 m Hg. Now it's renamed "Baipa". 1 millibar is equal to 100 pa (hectopascals).

invent

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The concept of millibar was invented by Mr. Napier Shaw in 1909, and was internationally recognized in 1929. Unicode symbol is "mb" (? )。

analyse

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1 millibar means that a force of 1000 dynes is exerted on an area of 1 cm2. For example, the air pressure is 1000mb, which means that the force per square centimeter at that time is 1 000,000 dynes.

Dyne is the unit of force. In the cm-g-s system, it means the force acting on an object with a mass of one gram to make it move at a speed of1cm/s 2. Dyne is a small force. In summer, we see that the force of ants carrying grass stems is 100 dyne. It can be seen that the power of a dyne is small.

Millimeter and millibar can be converted to each other. According to the relationship between pressure and mercury column height: p (pressure) =h (mercury column height) × d (mercury density at 0℃)

The air pressure is mercury column height1mm = 0.1cm×13.596g/cm3 =1.3596g/cm2.

At the sea level at latitude 45, the weight of 1g =980.6 dynes.

Therefore:1mm =1.3596× 980.6 =1333.22 dynes/cm2 =1.33322 millibar =3/4 millibar.

According to this relationship, when the air pressure is 760mm, it is equivalent to1013.25mbar, which is called a standard atmospheric pressure.

The average sea level pressure is 10 13.25 hectopascals (millibars). This value decreases with the increase of height.

App application

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Millibar is a physical unit used to measure pressure. Millibar is not an SI unit. The international unit is Pascal (Pa),1mbar =100pa =1HPA = 0.1kpa. Nevertheless, millibar is still a common unit in many occasions.

For a long time, meteorologists all over the world have regarded millibar as one of many units for measuring the atmosphere. It will take some time for Sl units to be widely adopted. Millibar is still widely used, although officials in various countries are gradually transitioning to the same numbered Sl unit: hPa. However, in other fields, hecto prefix representing one hundred is rarely used, so kilopascals are usually used instead. For example, the weather forecast in Canada is usually in kilopascals.

Today, millibar is usually used to refer to hurricanes or tornadoes, because lower central air pressure means higher wind speed and more power.

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