What is atmospheric pressure?
The weight of the column of air contained in a unit area from mean sea level to the top of the atmosphere is called atmospheric pressure. Atmospheric pressure is also defined as the force that acts normally on a unit area around a point due to the column of atmosphere above that point. Atmospheric pressure is also known as air pressure. Read the article till the end to know details about atmospheric pressure.
Facts related to atmospheric pressure
Several important things can be kept in mind about atmospheric pressure. The following are important things to know about atmospheric pressure:
- This force per unit area Is measured in.
- to atmospheric pressure ‘millibar’ Or expressed in mb. For the purposes of using it kilo pascal Also measured in.
- Aneroid barometer or mercury barometer is an instrument used to measure atmospheric pressure.
- The rate of change of pressure with respect to distance is the pressure gradient.
Vertical variation of atmospheric pressure-
In the lower atmosphere the pressure decreases rapidly with altitude. The decrease in pressure with altitude, however, is not constant. Since the factors controlling the density of air – temperature, amount of water vapor and gravity are variable. There is no simple relationship between altitude and pressure.
In general, atmospheric pressure decreases at an average rate of about 34 millibars per 300 meters of altitude. The vertical pressure gradient force is much larger than the horizontal pressure gradient. But, it is generally balanced by an approximately equal but opposite gravitational force. Therefore, we do not experience strong winds.
A low-pressure system is surrounded by one or more isobars with the lowest pressure at the center.
Horizontal Distribution of Atmospheric Pressure-
- Horizontal distribution of pressure is studied by drawing isobars at constant levels.
- Isobaric lines are lines joining places of equal pressure. To eliminate the effect of altitude on pressure, it is measured after lowering it to sea level at any station for comparison purposes.
- There are clearly identifiable areas of homogeneous horizontal pressure regimes or ‘pressure belts’. There are a total of seven pressure belts on the Earth’s surface.
That’s seven pressure belts.
- take the equator pressure belt, Located between 10°N and 10°S latitudes. This belt is an area of convergence of trade winds from the two hemispheres from the subtropical high pressure belt. This belt is also called Doldrum.
- subtropical high pressure belt, Subtropical highs extend from near the tropics from about 10°N and S to about 35°N and S.
- sub-polar low pressure belt, It is located between 45° north and south latitude and the Arctic and Antarctic Circle (66.5° north and south latitude).
- polar high pressure belt, The polar high regions are smaller and spread around the poles. These are located around the poles between 80-90° north and south latitudes.
These pressure belts can be seen in the given globe:
Value of atmospheric pressure-
- 1 Atmospheric Pressure is equal to 1,013 millibar.
- Atmospheric pressure in bars: 1.01325 bar
- The atmosphere exerts a pressure of 1034 grams per square centimeter at sea level. This amount of pressure is exerted by the atmosphere on all animals, plants, rocks, etc. at sea level.
- Sea level pressure is low near the equator and the area is known as the equatorial low. High pressure areas are found along 30° North and 30° South, which are called subtropical high. Further poleward along 60° North and 60° South, low pressure belts are called subpolar lows. The pressure is higher near the poles and is called polar high.
Atmospheric pressure formula-
P = F/A = (m*g)/A, where A is the surface area. Atmospheric pressure is thus proportional to the weight, pressure (p), mass (m), and acceleration due to gravity (g) per unit area of the atmospheric mass above that location.
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