What is atmospheric pressure?

Arab weather - atmospheric pressure is of great importance in meteorology, as it provides information about the air at the top, as the decrease in atmospheric pressure indicates that the air is distributed in that area or is missing from it. As for the rise in atmospheric pressure, it indicates the addition of air to the top, affecting Atmospheric pressure affects the movement of air systems, the distribution of air masses, and the behavior of winds around the world.

What is atmospheric pressure?

Atmospheric pressure is defined as the weight of the air column located on a unit area of 1 cm² in any area on the Earth's surface, so that the weight of the air column in fact represents the pressure group of the gases from which it consists in fixed proportions.

Atmospheric pressure is measured in millibars, which is the dynamic unit of atmospheric pressure force.

What are the factors affecting the rise and fall of atmospheric pressure?

Atmospheric pressure is affected by several things, perhaps the most important of which are:

• temperature

Atmospheric pressure is mainly affected by temperatures, low atmospheric pressure often indicates higher temperatures, and high atmospheric pressure indicates lower temperatures. .

And the exact opposite happens in cold air. When temperatures drop, the air shrinks, its density increases, and it becomes heavier in weight, and thus the atmospheric pressure rises, provided the humidity levels are constant.

• Humidity

Atmospheric pressure is also affected by humidity, because moist air is lighter in weight than dry air, depending on its temperature.

• Landforms

The terrain is an important factor in influencing the behavior of atmospheric pressure. Air falling on a unit area of 1 cm² leads to a rise in surface atmospheric pressure.

• The difference in specific heat between land and water

Perhaps the difference in specific heat between the surface of the land and water is one of the reasons for the decrease and rise in atmospheric pressure , as the heat range on land is greater than that of water, so the surface of the earth heats up faster than the surface of the water, causing a decrease in atmospheric pressure over the land, and the atmospheric pressure above the surface of the water is high in relation to the pressure Atmosphere on land, and vice versa, at night, when the surface of the earth cools rapidly and the water remains warm, and the atmospheric pressure above the surface of the earth becomes high relative to the atmospheric pressure above the surface of the water.

Atmospheric pressure has fixed ranges around the world, so what are they?

There are four constant atmospheric pressure bands around the world throughout the year, which are:

• low tropical pressure

This range of atmospheric pressure extends between two latitudes (5) north and south of the equator, and the decrease in atmospheric pressure in this range is due to the rise in temperature as a result of permanent solar heating on the equator, and an increase in humidity. It is characterized by its quiet air for a long period of time.

• high orbital pressure

This range of atmospheric pressure extends between two latitudes (25 - 35) north and south of the equator, and the rise in atmospheric pressure in this range is due to the fall of air masses coming from the upper layers of the atmosphere.

• low subpolar pressure

This range of atmospheric pressure extends between two latitudes (45 - 60) north and south of the equator, and the decrease in atmospheric pressure is attributed to the convergence of air masses of different characteristics in that range.

• high polar pressure

This range is permanently centered in the north and south poles, and the increase in atmospheric pressure in these two regions is due to the drop in temperatures.

Symbols indicating atmospheric pressure values

1. Low atmospheric pressure is denoted by the symbol (L) or (_)
2. High atmospheric pressure is denoted by the symbol (H) or (+).

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