Why is it windy?

Winds form when the air pressure is different from one area to another. When the temperature is high, the air will rise, the air pressure in the original area will decrease, and the high-density cold air will flow to fill the position below the warm air flow. This flow of gas is wind. In some places on Earth, winds blow all the time. These are the prevailing winds, which determine weather patterns on Earth.

Nighttime land breeze

At night, the temperature drops faster on land than on the ocean, and the cold air sinks to Over the land and toward the ocean, the air above the ocean is still warm, so it rises. Cool air moves toward the ocean to replace warm air, creating breezes from the land.

Daytime sea breeze

On a hot, clear day, the warm air above the land rises and is replaced by the sea breeze. The cold air moving towards the land creates sea breeze.

How is the wind produced?

When the hot air rises, the air pressure in the original area decreases, and the air will flow from the surrounding area. Areas of high pressure move here.

When cold air descends, it creates an area of ​​high pressure, and the air in the high-pressure area moves toward the low-pressure area.

Earth's trade winds

Winds blow from areas of high pressure to areas of low pressure. The trade wind is a type of wind that blows close to the ground from the subtropical high pressure area at 30 degrees latitude to the equatorial low pressure area. This kind of wind appears regularly in a fixed area, and the direction of the wind remains unchanged. It is very "trustworthy", so people call it the trade wind. In the Northern Hemisphere, the wind blows from the northeast to the southwest, called the "Northeast Trade Wind"; in the Southern Hemisphere, the wind blows from the Southeast to the Northwest, called the "Southeast Trade Wind."

Wind speed

Wind blows from the center of the high pressure area to the center of the low pressure area. The closer the distance between the two centers, the greater the wind speed between them. Wind speed is divided into 0-12***13 levels according to the strength of the wind.

Windsocks are used at small airports to indicate wind strength and direction to pilots. A loose windsock means the wind is very light. When the wind is strong, the windsock will bulge. Towards the direction the wind is blowing.

High in the clouds

Clouds can give us our best clues about recent weather conditions. When the temperature is high, moist air from the earth's surface rises into the air and then cools down. When cooled to a certain extent, the water vapor in the air turns into small water droplets. This process is called condensation. When countless small water droplets gather together, they form clouds.

"Fish-scale sky"

Cirrocumulus clouds are sometimes called "fish-scale sky" because of the The pattern is like fish scales. This kind of cloud is composed of ice crystals, and the appearance of "fish scale sky" indicates that the weather conditions are unstable.

Types of clouds

There are three main types of clouds - hairy cumulus clouds, divided into several layers Stratiform clouds and feathery wavy clouds. These three basic cloud shapes can also be combined to produce other cloud shapes.

Cumulus clouds sometimes look like floating clumps of cotton. They can form over land in dry, clear weather if they gather together. It might rain.

The size of clouds varies depending on the temperature. If a cloud is blown into cold air, more water vapor will condense, and the cloud will grow larger. If the cloud is blown into hot air, some of the water droplets in it will evaporate and the cloud will become smaller.

Horsetail clouds

Most clouds are composed of countless small water droplets, but cirrus clouds (or horsetail clouds) Clouds) are made of ice crystals. This is because they form high in the sky, where the air is extremely cold.

Cumulonimbus

Cumulonimbus (or anvil cloud) is a large thundercloud with a flat top , extending vertically. They often have thunder and lightning.

Altocumulus

Altocumulus is a mixture of ice and very cold water. They look like flat white or gray clouds. They sometimes herald a thunderstorm at the end of a long period of muggy weather.

Dark rain clouds will cover the entire sky and block the sun. Nimbus clouds bring rain or snow.

Think about it

If you put a mirror over the steam coming out of a thermos. What do you see forming on the cold mirror? This is the process of condensation. It is also the process of cloud formation.

On cold, clear nights, the ground often cools down quickly because there are no clouds in the sky to retain heat. Fog forms when air near the ground cools and water vapor condenses into tiny water droplets.

Smog occurs when fog forms in a smoky or polluted area, such as a large city.