Millibar
Also called: Hectopascal · Topic: Atmospheric Pressure, Winds and General Circulation · NCERT: Class 11, Ch 9 "Atmospheric Circulation and Weather Systems"
Meaning
A millibar (mb) is a unit for measuring atmospheric pressure, which is the weight of the air above a place. One millibar equals one hectopascal (hPa), which is 100 pascals. Weather maps now use hPa, but the numbers are the same as in millibars. The average pressure at sea level is about 1,013.2 mb, and the standard value is 1,013.25 mb. This is equal to 760 mm of mercury.
Example
At sea level in Mumbai, pressure is close to 1,013 mb. At Khardung La in Ladakh, high in the mountains, it is only about 650 mb. The air there is thinner and has less oxygen, so visitors need time to adjust.
Don't confuse with
- Millimetre of mercury (mm Hg): this also measures pressure, but by the height of mercury in a barometer tube. 1,013.25 mb is the same as 760 mm Hg, so the two numbers are not the same scale.