ATMOSPHERIC PRESSURE
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| ATMOSPHERIC PRESSURE -Barometer |
One atmospheric pressure (76 cm of mercury) = 760 mm of Hg =1013.25 milibars (mb).
The modern metric unit of pressure measurement is the milibar (mb), one milibar being equal to the pressure necessary to support 0.75 mm of mercury column.
The mean sea level pressure of the atmosphere is 1013.2 mb.
Atmospheric pressure is affected by altitude, by temperature and by Earth rotation.
Atmospheric pressure can be measured by Barometer.
BAROMETER
A barometer is a scientific instrument used in
meteorology to measure atmospheric pressure. A simple
barometer consists of a long glass tube (closed at one end, open at the other)
filled with mercury and turned upside down into a container of mercury.
PRESSURE BELTS
EQUATORIAL LOW PRESSURE BELT (OR DOLDRUMS)
From 50 North to 50 South.
Tremendous heat on equator thus warm air rises creating low pressure.In this region wind speed is very low, that's why called Doldrums (Belts of Calm).
TROPICAL HIGH PRESSURE BELT (HORSE LATITUDES)
From 300 North to 350 South.
Usually high temperature in this region except two months.
Due to high pressure in this region there is difficult to cross this region by a ship.
Here the pressure is high, although high temperature because here pressure depend on the rotation and movement of air, (as winds from Doldrums belt rises up and accumulate here.Also winds from Sub-Polar Low Pressure Belt accumulate here).
SUB-POLAR LOW PRESSURE BELT
From 600 North to 650 South.
In this region low pressure is created because of intense high pressure at the poles.
POLAR HIGH PRESSURE BELT
From 650 North to 900 South.
High pressure exist due to very low temperature here.
50 N to 50 S
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Doldrums
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50 to 300 N and S
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Trade Winds
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300 to 400 N and S
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Horse Latitudes
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350 to 600 N and S
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Westerly Winds
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400 S
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The Roaring Forties
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500 S
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The Furious fifties
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600 S
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The Shrieking
Sixties
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