Arabia Weather - Atmospheric pressure is the weight of the air column affecting a unit area, and it extends vertically from sea level to the end of the atmosphere. There are different air pressure systems such as air depressions and air highs, and this depends on the amount and value of the air pressure in the center of each of them. If The air pressure in the center is low, and increases as we move away from it, it is called an air depression. If the air pressure is as high as possible in the center, and decreases as we move away from it, it is called an air high.
An air depression is a closed area with equal lines of pressure, where the lowest value of air pressure is in the center, as a result of the decrease in the weight of air masses resulting from an increase in their temperature. The value of air pressure increases as we move away from the center. The wind direction around the center of the air depression is counterclockwise in The Northern Hemisphere, and vice versa in the Southern Hemisphere, and the depression is symbolized by the letter “ L ”.
The decrease in pressure coincides with lighter air, so it rises to the upper layers of the atmosphere, and rotates around the center of the depression in a counterclockwise direction in the northern hemisphere and clockwise in the southern hemisphere. When the air rises and cools, its water vapor content condenses, and clouds are formed. Mostly, a depression is accompanied by rain, strong winds, and low temperatures.
For example, when a hot, humid tropical front meets a cold, dry polar front, the hot air forms something like a tongue under the cold air, raising it upward, as it is lighter. Consequently, the air pressure in this region decreases, so the air cools and water vapor condenses, then clouds are formed. .
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