The atmospheric pressure maps and the instruments of measuring the atmospheric pressure
The atmospheric envelope of the Earth
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 .
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
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 normal atmospheric pressure is the atmospheric pressure at the sea level and it equals 1013.25 mb .
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 .
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 .
The atmospheric pressure instruments
The atmospheric pressure is measured by the barometers , One of these barometers is Aneroid which is a type of the barometers that is used to determine the possible day weather .
|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 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 .
The wind moves from the areas of the high atmospheric pressure to the areas of the low atmospheric pressure .