How is the sky cloudy?

Clouds floating in the sky are composed of many tiny water droplets or ice crystals, some of which are mixed together, and sometimes there are some larger raindrops and ice particles. The bottom of the cloud does not touch the ground and has a certain thickness.

The formation of clouds is mainly caused by water vapor condensation.

More than ten kilometers from the ground, the closer to the ground, the higher the temperature and the denser the air; The higher the altitude, the lower the temperature and the thinner the air.

On the other hand, the water surface of rivers, lakes and seas, as well as the moisture of soil, animals and plants, evaporate into the air at any time and become water vapor. After water vapor enters the atmosphere, it forms clouds to cause rainfall, or condenses into frost dew, and then returns to the ground, permeates the soil or flows into rivers, lakes and seas. Later evaporation (sublimation), condensation (condensation), dripping. The cycle is endless.

After the water vapor enters the lower atmosphere from the evaporation surface, the temperature here is high and it contains a lot of water vapor. If the hot and humid air is lifted, the temperature will gradually decrease, and when it reaches a certain height, the water vapor in the air will reach saturation. If the air continues to be lifted, there will be excess water vapor precipitation. If the temperature there is higher than 0℃, the excess water vapor will condense into small water droplets. If the temperature is lower than 0℃, excess water vapor will condense into small ice crystals. When these small water droplets and small ice crystals gradually increase to a level that can be recognized by human eyes, it is a cloud.

See the weather from the clouds.

"The sky is hooked with hook clouds, and the ground is dripping with rain": "Hook clouds refer to cirrus clouds. Behind this cloud, there are often fronts (especially warm fronts), low pressure or low pressure troughs moving, which indicates that rain is coming;

"Battery cloud, rain": Battery cloud refers to fort-shaped high cumulus cloud or fort-shaped stratocumulus cloud, which appears in front of the trough with low pressure, indicating that the air is unstable, and thunderstorms usually come every 8- 10 hours.

"Clouds twist, and it rains": Cloud-to-cloud means that the upper and lower layers of clouds move in different directions, that is to say, the height and wind direction of clouds are different, which often occurs near the front or low pressure, so it indicates rain, and sometimes the wind direction of clouds is opposite to the ground, and there is a saying that "the sky will change when the clouds go against the wind".

"The river pig crossed the river and it rained cats and dogs": The river pig refers to the broken rain clouds in nimbostratus. The appearance of this cloud indicates that there is a lot of water vapor in nimbostratus, and heavy rain is coming. Sometimes broken rain clouds are blown to cloudless places by strong winds, and it is also a precursor to rain to see clouds like river pigs floating across the "Milky Way" at night.

"Cotton cloud, rain is coming": Cotton cloud refers to flocculent cumulus clouds, indicating that the middle atmosphere is very unstable. If there is enough water vapor in the air and there is upward movement, cumulonimbus clouds will form and thunderstorms will come.

"Gray cloth hangs over the sky, and the rain will continue": Gray cloth cloud refers to nimbostratus, which is mostly formed by thickening and metamorphosing high-level clouds, with a large and thick range, and sufficient water vapor in the clouds, which often produces continuous precipitation.

"Cloud to the east, chariots and horses to; The clouds go south and the water rises; Clouds to the west, covered with hemp fiber; Clouds going north are good for drying wheat ":according to the moving direction of clouds, it is predicted that the weather will be fine, and the clouds will move east and north, indicating that the weather will be fine;" "The movement of clouds to the west and south indicates that it is going to rain. The direction of cloud movement usually indicates the wind direction at its height. This proverb shows the distribution of clouds in different parts of low pressure. Suitable for all-day dense, low and fast-moving clouds.

"Fish-scale day, even if it doesn't rain, there will be wind": Fish-scale day refers to cirrocumulus. The appearance of such clouds indicates that the upper atmosphere is unstable. If the clouds continue to decrease and thicken, it means that this area is already in front of a trough with low pressure, and it will rain or wind soon.

"Carp spots in the sky don't need to be turned over by the sun": Carp spots refer to translucent cumulus clouds, which are often controlled by denatured high-pressure air masses that turn from cold to warm. If the clouds don't continue to thicken, it will be sunny in the short term.

"Dark clouds catch the sunset, and it will not fall tomorrow or tomorrow": When the sun sets, a wall-like dark cloud rises under the western horizon to catch the sun, indicating that the dark clouds are moving eastward, and the rainy weather system in the west is moving, and it is going to rain. Generally speaking, if the clouds catch up, it will rain that night; If it is connected with the high clouds, it will rain the next day. However, if the dark clouds in the west are lumpy or discontinuous, or some areas are cloudy, it is not a sign of rain in the future.

"The northwest sky is unlocked, and the sun shines brightly": On rainy days, the clouds in the northwest crack and reveal a blue sky, which is called "the sky is unlocked". This shows that the local area is at the back of the rainy weather system. As the rainfall system moved eastward, the rain stopped and the weather improved.

"Now the sun appears, but it hasn't been seen for three days": in spring and summer, at noon on rainy days, the clouds split and the sun appeared, but the clouds quickly gathered and became thicker, indicating that the local area was affected by the quasi-static front, and the airflow near the quasi-static front rose strongly and changed greatly. When the updraft increases, the clouds become thicker and the rainfall increases. When the updraft weakens, the clouds become thinner and the rainfall decreases or stops; Around noon, the sun shines strongly, the upper part of the cloud is heated and evaporated, or the updraft below the cloud weakens, and the zenith cloud will split. With the weakening of solar radiation or the strengthening of updraft under clouds, the divided clouds will regroup and become thicker. So "the sun appears now" often indicates that it will continue to rain. This proverb is similar to proverbs such as "the sun smiles, drenches the temple" and "the light shines, and the waste falls".

"Sunset shines at the foot, and the rain falls within three days": refers to the sun shining through the cracks in the clouds, which is called "the sun shines at the foot". It appears in the evening, indicating strong convection and indicating rain.

"Don't go out in the morning and take Wan Li Road at night": There are no clouds in the east and clouds in the west in the morning. Sunlight shines on the clouds and scatters rosy clouds, indicating that there is a lot of water vapor in the air or a rainfall system is moving in. During the day, the air is generally unstable and the weather will turn rainy. If there is a sunset glow at night, it means that the sky in the west has cleared up, and the general convection is weakened at night. The clouds in the east that form the rosy clouds will move eastward or tend to dissipate, indicating that the sky is clear.

"Long sunny, foggy and cloudy, long cloudy and foggy and sunny": refers to the appearance of fog after a long sunny day, indicating that the warm and humid airflow moves and the air is humid, which is a sign of cloudy and rainy; Fog appears after a long cloudy day, indicating that the clouds in the sky become thinner, split and dissipate, and the ground temperature drops, so that water vapor condenses into radiation fog. After sunrise, the fog will disappear and sunny days will appear.

In the morning of warm season, if there is a castle cloud on the horizon, it means that the humid atmosphere at this height is already very unstable. At noon, once the low-level convection develops, the upper and lower unstable layers will merge, resulting in strong convective movement, cumulonimbus clouds and thunderstorms. So there is a proverb "pagoda clouds in the morning, and it rains cats and dogs in the afternoon".

In addition, clouds with weather omen often have certain continuity, seasonality and locality in the evolution process. Clouds in the sky move from a distance in the order of cirrus, cirrostratus, stratus and nimbostratus, and gradually change from less to more, from high to low, from thin to thick, indicating that rainy weather is coming; On the contrary, if the clouds change from low to high, from thick to thin, and from layered clouds to scattered clouds, there will be no rainy weather. In the morning of warm season, if there are flat, convex and isolated clouds (light cumulus clouds) or fast-moving white broken clouds (broken cumulus clouds) in the sky, it means that the air in the middle and lower layers is relatively stable and the weather is fine.

In addition, the color of clouds can also indicate some kind of weather. For example, the color of hail cloud is first white and then black, and then red appears in the cloud, forming a white, black and red distorted cloud with khaki edges. Black is caused by the sun's inability to penetrate clouds; White is the result of non-selective scattering or reflection of sunlight by clouds; Red and yellow are the phenomena that some cloud droplets (ranging from one thousandth to one hundredth of a millimeter in diameter) selectively scatter sunlight. Sometimes rain clouds are pale yellow, but the color of the clouds is uniform and will not stir. There are also many proverbs that hail comes from the color and shape of clouds. For example, there is a proverb in Inner Mongolia, such as "If you are not afraid of dark clouds, you are afraid of dark clouds and red clouds, and you are most afraid of white worms in Huang Yun". Stir clouds and hail in groups; There are proverbs such as "When clouds fight, hail will fall" and "Huang Yun has red clouds and many hail disasters". There are also sayings such as "Dark clouds roll into a ball in the afternoon, rain and hail come together", "It's yellow and sultry, and the Tianhe water roar to prevent ice eggs", all of which show that when the air convection is strong, the clouds develop rapidly and rush up like smoke. parents