Determinants of Air Pressure

Determinants of Air Pressure

Air pressure is the weight of air. Because air is made up of many gases, it has a certain weight. Air pressure is the weight of air on any unit of area on Earth and is measured in millibars. Air expands in summer due to the heat and contracts in winter.

When the temperature is high, the air is thin, and there is less pressure, and when the temperature is low, the air is thick, and there is more pressure. As a result of the difference in air pressures, air movement from high to low-pressure locations occurs; this is known as wind.

Temperature and air pressure cause air to expand and contract, generating heat and moisture to be distributed throughout the environment. The average air pressure at sea level is 1013.2 millibar in typical circumstances. Air pressure is measured through a device called a barometer.

After understanding what air pressure is, let’s discuss the distribution of air pressure. 

Distribution of Air Pressure

Because air is prevalent all over the planet, it can be dispersed horizontally or vertically.

1. Horizontal Distribution

The air pressure in a given location varies throughout the day and night, as well as in the summer and winter, although the average air pressure conditions stay consistent. When we look at how air pressure is divided on Earth, we can see numerous high- and low-pressure zones. Isobars are used to depict these distinctions on maps.

In general, there are two types of air pressure:

1. High pressure.
2. Low pressure.

Seven air pressure belts can be observed on Earth due to the combined effects of many causes affecting air pressure at various latitudes.

2. Vertical Distribution

Because air is a combination of gases, it is highly compressible. As a result, it has the highest density at the lowest levels, where the bulk of air above squeezes it. As a result, the atmosphere’s lower layers have a high density and pressure. On the other hand, the higher strata are less compacted and have a lower density and pressure. The atmosphere grows thinner as we ascend, resulting in more scattered molecules and lower pressure due to increased inter-molecular space.

The air pressure is nearly two-thirds lower at the summit of Mt. Everest than it is at sea level. However, the drop in pressure with altitude is not consistent. There is no clear link between altitude and pressure because the factors regulating air density—temperature, water vapour, and gravity—are all variable. Every 300 metres of height, the air pressure drops by roughly 34 millibars on average.

Factors That Influence Air Pressure

1. Altitude

As the altitude rises, the length of the overlying air column on the earth’s surface diminishes, and the weight or pressure applied by the atmosphere reduces as well.

2. Ambient temperature

When the atmosphere’s temperature rises, the air expands and loses density; conversely, when the temperature drops, the air gets denser, and its pressure increases naturally.

3. Water vapour

Because water vapour is lighter than dry air, the air pressure will be lower if the amount of water vapour in the air is considerable, and vice versa.

4. Air currents and atmospheric pressure

When the temperature rises in an area, the air becomes lighter and rises; as a result, a low-pressure forms, and cooler air descends to fill the space and neutralise the low pressure.

5. Change of scenery

The air warms up faster, becomes lighter, and forms a low-pressure band in the equatorial region. As cold air falls to the poles, a high-pressure zone forms.

Conclusion

Because air is a physical substance, it exerts pressure on the earth’s surface. Rather than measuring force itself, we measure force per unit area. This is why atmospheric pressure is defined as the force exerted per unit area, on the unit area of the earth, by the weight of the air. When examined diurnally, air pressure has a distinct rhythm. The major causes of diurnal pressure changes are solar heating and terrestrial radiation.

Fast blowing winds are caused by a difference in air pressures near the earth’s surface, but because air pressure falls as height increases, humans do not experience fast blowing upward winds. The reason for this is that as the height of the Earth increases, so does its gravitational force.