What Is a Millibar?

Overview

Overview

The unit of high or low air pressure is represented by the pressure of the mercury column per unit area. In physics, the unit of pressure is expressed by "bar": a force of one dyne per square centimeter of area is called one bar. Meteorologically, this unit is considered too small, taking 1,000,000 dyne / cm2 as 1 bar, and taking one thousandth of a bar as a unit of air pressure, called 1 mbar. One millibar is one thousandth of a bar, which is equal to a pressure of 0.76 millimeters of mercury. Now renamed "100 Pa". 1 mbar is equal to 100 Pa (hPa).

Chinese name

millibar

Nature

Physics concepts

inventor

Napier Shaw

Symbol

mb

Millibar invention

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

Mbar analysis

One millibar means a force of 1,000 dyne over an area of one square centimeter. For example, a pressure of 1000 mb means that the force of the atmospheric column at that time was 1,000,000 dyne per square centimeter.

Dyne is a unit of force. In the centimeter-gram-second system, it represents the force acting on an object with a mass of 1g and causing the object to move at an acceleration of 1cm / s ^ 2. Dyne is a small force. In summer, the ants we saw holding small grass stalks had 100 dynes. It can be seen that the power of one dyne is small.

Millimeters and millibars can be converted to each other. According to the relationship between pressure and the height of the mercury column: P (pressure) = h (mercury column height) × d (density of mercury at 0 ° C)

The air pressure is the height of the mercury column 1 mm = 0.1 cm x 13.596 g / cm 3 = 1.3596 g / cm 2

At a sea level of 45 ° latitude, 1 gram weight = 980.6 dyne

Therefore: 1 mm = 1.3596 × 980.6 = 1333.22 dyne / cm2 = 1.33322 mbar = 4/3 mbar

According to this relationship, an air pressure of 760 mm is equivalent to 1013.25 mbar. This value is called a standard atmospheric pressure.

The average sea level pressure is 1013.25 hPa (mbar). This value decreases as the height increases.

Millibar application

Millibar is a physical unit used to measure pressure. Millibar is not an SI unit. The SI unit is Pascal (Pa), 1mbar = 100 Pa = 1 hPa = 0.1 kPa. However, mbar is still a common unit in many cases.

Meteorologists around the world have long used mbar as one of many units for measuring atmospheric radon. This caused the Sl unit to be widely adopted for some time. Millibars are still widely used, although officials in various countries are gradually transitioning to the same Sl unit: hPa. However, because hecto prefixes representing a hundred are rarely used in other fields, kilopascals are usually used instead. For example, in Canadian weather forecast, kPa is usually used as the unit.

Today, mbar is often used when referring to hurricanes or tornadoes, because lower central pressure means higher wind speeds and more power.