What is a low pressure and what is a high pressure? About the change in weather

What is a low or high pressure?

When you're planning a weekend of surfing or a family trip to the beach, you're probably concerned about the weather forecast. If you watch the weather forecast on TV, you may hear the weatherman say "low pressure will develop over the weekend" or "high pressure will develop".
There are vague images of "low pressure = bad weather" and "high pressure = better weather".
However, I think there are not many people who know about low pressure and high pressure in detail, so I will introduce low pressure and high pressure here.

What is a low pressure?

The "barometric pressure" of a low or high pressure is the pressure of a gas and generally refers to the pressure of the atmosphere.
When the pressure is low, it is called a low pressure, but there is no standard for a low pressure below 0 hPa. Low pressure is relative, when it is low compared to the surrounding pressure
It is called a low pressure.

The air is thinner than its surroundings in the "low" part of the region where the pressure is lower than its surroundings.
The air is denser in the higher pressure areas around the low compared to the low.
Therefore, the air in the high pressure area, where the air is dense, will move towards the low pressure area, where the air is thin. This causes the wind to blow towards the low pressure.
That way, after the air that flowed in collided with each other, the only place to escape was up and down
and down. The upward wind (updraft) is generated because of the ground.
In the air, there is originally a lot of water vapor, and this water vapor goes up into the sky on the updraft.
Since there is cold air in the sky above, the water vapor on the updrafts is cooled down to form water droplets and ice, and the grains of these water droplets are called clouds.
These water droplets and grains of ice collide with each other and become large and heavy, so they cannot float in the air and fall as rain or snow.
This is why, when there is a low pressure on the weather map, it becomes cloudy at the center of it, or rain or snow falls and causes the weather to break down.
What is a low pressure?

What is a high pressure?

The high pressure causes the exact opposite of the low pressure.
The air is denser in the "hyperbaric" areas where the pressure is lower than the surrounding area.
The low air pressure areas around high pressure are thin compared to high pressure.
Therefore, air is blown out to take air from the high pressure area to the low pressure area.
When that happens, there is no air in the high pressure area, so air comes down from above to take in air.
Therefore, when there is a high pressure, even if there are clouds in the sky above, they will be scattered into the air by the downward wind. Therefore, when a high pressure system arrives, the clouds above will disappear and the weather will clear up and improve.

What is an anticyclone?

Why does the low pressure occur?

Low pressure is a place where the air is thinner than the surrounding area, which may raise the question of why such a place is created.
During the day, when the sun is out, its light hits the ground. However, in doing so, for some reason
The sun's rays don't hit the ground evenly, and only one area of the ground may be heated and have heat. This is when the low pressure occurs.
This is because when the ground warms up, the air above it also warms up. Warmed air rises because it has the propensity to go up. That way, the area where the air has risen will have less air, so air will move in from around it, creating a low pressure.

Front related to rainfall

At first glance, it looks like a low pressure = bad weather = low temperature, but a low pressure is a collection of warm air. This boundary between warm and thin air and normal air is called the front.
If there is a low pressure in the middle, it will be in the form of a front on the right and a front on the left, but these two fronts are very different in nature.

The front on the right in the figure below is called a "warm front" because when it passes through this front, it is taken into the warm air of a low pressure and the air temperature rises.
On the other hand, if a front on the left passes through while in a warm low pressure, it will be thrown out into the normal air and the temperature will drop, so it is called a cold front.

In the case of a warm front, warm air flows into the cold air, but the warm air is so warm that it slides over the cold air as it rises. On the contrary, cold fronts allow cold air to flow into warm air. The cold, chilly air is heavy compared to the warm air, so it slides down.
In fact, this difference can make a big difference in the weather.
In the case of a warm front, the air moves gently and water vapor evaporates along the air, forming clouds.
On the other hand, a cold front is characterized by the fact that the boundary between cold and warm air is steep and clouds tend to gather in one place.
Depending on these characteristics, there are different types of clouds. Clouds formed in a warm front tend to form stratospheric clouds, while those in a cold front tend to form cumulonimbus clouds.
As a result, there will be strong showers and cooler temperatures under a cold front. On the other hand, when a warm front passes through, there is a long period of moderate rain and the temperature rises.
So, before you go out to surf or go to the beach, make sure that a cold front does not pass through.

What is a low pressure and what is a high pressure? About the change in weather