Atmospheric pressure maps and the instruments of measuring 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 pressure on all the living organisms and the non-living things on the Earth’s surface. This pressure is known as 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 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 is 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.