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Friday, July 18, 2014

The atmospheric pressure maps and the instruments of measuring the atmospheric pressure


The air pressure

The atmospheric envelope of the Earth

 

You should know that the Earth is surrounded by a gaseous envelope known as the atmospheric air or the atmospheric envelope which is a gaseous envelope rotating with the Earth around its axis , and it extends about 1000 km above the sea level  .

 

You should know that the atmospheric air causes the pressure on all the living organisms , and the non - living things on the Earth's surface . This pressure is known as the atmospheric pressure .

 

 The atmospheric pressure

 

You should know that the atmospheric pressure is the weight of the air column of an atmosphere height on a unit area  , and it is measured by a unit called a bar or millibar .

The atmospheric pressure
1 bar = 1000 millibar ( mb ) .

The normal atmospheric pressure is the atmospheric pressure at the sea level and it equals 1013.25 mb .

 

You should know that the atmospheric pressure differs from one place to another according to some effects , And the change of the height from the sea level is one of these effects .


 

You should notice that 50 % of the mass of the atmospheric air is present in the area between the sea level and 3 km height , and 90 % of the mass of the atmospheric air is present  up to 16 km height above the sea level . The density of the air decreases by increasing the elevation above the sea level .

Atmpspheric pressure
The relation between the altitude above the sea level and the pressure .

The atmospheric pressure instruments

 

You should know that the atmospheric pressure is measured by the barometers , One of these baromters is Aneroid which is a type of the barometers that is used to determine the possible day weather .


The anderoid barometer
Anderoid is used to determine the possible day weather .



The Altimeter is an instrument that used by the pilots in the  aeroplanes to measure the elevation from the sea level based on the atmospheric pressure .

The Altimeter
The Altimeter is used by the pilots in the aeroplanes .

The atmospheric pressure maps 

 

There are curved lines that join the  points of the equal pressure in the atmospheric pressure maps which is known as Isobar .

Atmospheric pressure maps
There are points of equal pressure that are joined by curved lines known as Isobar .

You should know that the wind moves from the areas of the high atmospheric pressure to the areas of the low atmospheric pressure .

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