The process of cloud formation is a process in which water vapor in the air reaches saturation or supersaturation through various reasons and condenses. Water vapor saturation in the air is a necessary condition for cloud formation. The main ways are as follows:
(1) The water vapor content is unchanged, and the air is cooled;
(2) keeping the temperature constant and increasing the water vapor content;
(3) Not only the water vapor content is increased, but also the temperature is reduced.
But for the formation of clouds, the cooling process is the most important process. In the process of cooling, the cooling effect brought by ascending movement is the most common.
Cumulonimbus cloud is a kind of cloud formed in the process of strong vertical convection. Because the ground absorbs much more solar radiation heat than the air layer, the ground temperature rises more during the day, especially in summer. Therefore, due to heat conduction and heat radiation, the atmospheric temperature near the ground rises, the gas temperature inevitably expands, the density decreases, and the pressure also decreases. According to the principle of mechanics, it will rise, and the density of the air layer above it is relatively high, and it will sink. In the rising process, the hot airflow expands and depressurizes, and at the same time, it exchanges heat with the high-altitude low-temperature air, so the water vapor in the rising air mass condenses, and water droplets appear, forming clouds. In the process of strong convection, the fog droplets in the cloud further cool down and become supercooled water droplets, ice crystals or snowflakes, and gradually increase with the height. At the freezing height (-10℃), due to the latent heat released by the freezing of supercooled water, the cloud top suddenly develops upward and spreads horizontally near the tropopause, forming a cloud anvil, which is a remarkable feature of cumulonimbus clouds.
In the process of cumulonimbus cloud formation, positive and negative charges are accumulated in different parts of the cloud under the simultaneous action of atmospheric electric field, temperature difference electrification effect and debris electrification effect. When the charge accumulates to a certain extent, it will discharge between clouds or between clouds and the ground, which is what people usually call lightning.
Lightning has brought great disasters to human society with its great destructive power, especially in recent years, lightning disasters have occurred frequently, and the harm to the national economy has become increasingly serious. It is necessary to strengthen the awareness of lightning protection, actively cooperate with meteorological departments, do a good job of prevention, and minimize the losses caused by lightning.
Question 2: How are thunderstorms formed? tornado
Thunderstorm, among the common natural phenomena, can be said to be the most touching. On a sultry summer afternoon, large clouds piled up in the sky. The temperature drops suddenly, followed by strong winds, showers, thunder and lightning, and sometimes hail. Irritable weather will soon become cool, refreshing and comfortable. The rain stopped, the wind stopped and the clouds dispersed. The blue sky was washed away by rain, which made it particularly bright. The setting sun shines on the wet earth ―― what a beautiful night!
In sultry summer, thunderstorm seems to be a kind of adjustment and a meditation endowed by nature. It turns out that in summer, the sun is facing the northern hemisphere, and the direct sunlight makes the water on the ground evaporate faster than in other seasons. As the temperature rises, the air near the ground can contain more water vapor. Even so, if there is no wind, the water vapor in the air near the ground will soon reach saturation, that is to say, it is impossible to contain more water vapor in the air. At this point, the water on the ground no longer continues to evaporate. We are sticky and wet, so you can fan as much as you like, and you can't sweat. We were drowsy and panting from the heat.
There is no wind in this sultry time, but don't think that the air is stagnant, and the air close to the ground is rising sharply. The rise of temperature and the increase of water vapor all reduce the density of air, which is commonly known as "light". Lighter air must rise. However, the sky is not as hot as the ground. The hot air near the ground gradually cools down with the rising, and the temperature drops by 100℃ for every rising100 meters. When the air gets cold, it can't contain as much water vapor as before, and some water vapor has to be broken and condensed into small water droplets. Seen from the ground, there are clouds in the sky.
Why don't these little drops fall into the rain at once? These small water stains are too small. It is the rising air that stops them from falling. In the hot summer afternoon, the air force rising on the ground is very strong, which not only holds the small water point, but also pushes the small water point higher and higher, so the clouds pile up higher and higher. The clouds generated in this way have a special appearance ―― they can often be seen in hot summer afternoons ―― and their feet are almost flat, with overlapping peaks, like snow-capped peaks and castles made of marble, and the light and shadow are particularly clear under the sunlight. This kind of cloud has a special term in meteorology, called cumulus. Its feet are about 2000 meters from the ground, that is to say, the hot air rising from the ground rises to that height, and the water vapor contained in it condenses into small drops. Its top may be above the ground 1 10,000 meters. It is very cold at such a high altitude, and the temperature is below the freezing point of water. If cumulus clouds pile up higher and higher, we can see that the top of cumulus clouds sticks out like an anvil used by blacksmiths to strike iron, surrounded by thin clouds like white scarves, which are ice flowers formed by water vapor.
Although cumulus clouds are like high peaks. It looks quiet, but its heart is churning violently. Small water droplets merged into larger water droplets and began to fall. The air rising from the ground is constantly rushing upwards, and the two are violently rubbed, so they are both charged: the rising air is negatively charged and the falling water drops are positively charged. Gradually, at the top of cumulus clouds, negative charges accumulate; At the bottom, positive charges accumulate. The ground is positively charged and negatively charged at the bottom of cumulus clouds.
The thrilling scene began at once: first, a strong wind blew people down, and then tiny raindrops. The big water droplets finally broke through the rising air and fell straight from the clouds. The hot air in the lower layer is drenched by rain, which suddenly cools, contracts and presses down the ground, so strong winds often come before the rain. At this time, there was a flash of dendritic lightning in the sky, followed by rumbling thunder. Lightning occurs between clouds and the ground, from the top to the bottom of cumulus clouds, and between two cumulus clouds. The air penetrated by lightning immediately exploded violently. If lightning is close to us, our eyes will shine, and then we will hear a clear thunderbolt; If you are far away from us, it will be a while before we can hear the thunder after the lightning. This is because the speed of sound is slower than the speed of light. Sometimes, the thunder rumbles for a long time, just like a wheel running over in the clouds. That's because clouds, mountains and the ground reflect thunder back and forth.
Thunderstorms sometimes have hail. Hail occurs when the ground is particularly hot, the air rises strongly, and the altitude is particularly cold. The top of cumulus clouds extends to the high altitude below freezing point, and some water droplets turned out to be ... & gt
Question 3: Why are there rainbows after a thunderstorm? Rainbow is an optical phenomenon in meteorology. When the sun shines on the water droplets in mid-air, the light is refracted and reflected, forming an arched color spectrum in the sky. There are different opinions about which seven colors the rainbow is. China is the most common (from outside to inside): red, orange, yellow, green, cyan, blue and purple. The western saying is: red, orange, yellow, green, blue, indigo and purple are the names taken by scientist Newton after decomposing seven primary colors. In fact, as long as there are water droplets in the air and the sun shines behind the observer at a low angle, an observable rainbow phenomenon may occur. Rainbow usually appears in the afternoon, when the rain clears. At this time, the air is less dusty and full of water droplets, and one side of the sky is dark because of rain clouds. However, observers can see the sunlight without being covered by clouds above or behind them, so rainbows are easier to see. Another place where rainbows are often seen is near waterfalls. Sprinkle water or spray fog in the air with your back to the sun on sunny days, or make rainbows artificially.
Question 4: Why are there rainbows after a thunderstorm? There will be a rainbow after the rain clears. It is related to the refraction of light.
When sunlight penetrates rain particles, a rainbow is formed. Originally, light travels in a straight line, but once it enters the water, it also has the property of refraction. So sunlight will be refracted when it passes through rain particles. At this time, because the angle of light refraction varies with different colors, seven colors will refract at different angles. So the seven colors will be arranged beautifully. This is the principle of forming a rainbow. Because the rainbow appears in the sky opposite the sun, if you want to see the rainbow after the rain, you should turn your back on the sun.
In summer, after the rain, the dark clouds fly away and the sun reappears. In the sky opposite the sun, there will be a semi-circular rainbow.
Rainbow is formed because sunlight is emitted in the air and refracted into water droplets.
We know that when sunlight passes through the prism, the direction of the foreground will be deflected and the original white light will change.
The line is broken down into seven color bands: red, orange, yellow, green, cyan, blue and purple.
After the rain, there are many tiny water droplets floating in the air. When the sun shines on them, they will refract and disperse.
Into seven colors of light. Many small water droplets refract sunlight at the same time, and then reflect into our eyes, and we will see one.
A semicircle rainbow. The ribbons of the rainbow are distinct, and the red ones are on the outermost side, followed by orange, yellow, green, cyan, blue and purple.
Color.
The size of water droplets in the air determines the bright color and width of the rainbow. When the water drops in the air are large, the rainbow is bright. also
Relatively narrow; On the contrary, if the water drops are small, the rainbow will be light and wide.
We can't see the rainbow when facing the sun, but only when facing the sun can we see the rainbow, so the rainbow in the morning appears.
In the west, the rainbow at dusk always appears in the east. But we can't see it. We can only see it from the sky by plane.
The appearance of rainbow is related to the weather change at that time. Generally, we can infer from the position of the rainbow in the sky that it will appear at that time.
It is sunny or rainy. When there is a rainbow in the east, it is not easy to rain locally, and when there is a rainbow in the west, it may rain locally.
Very sexual.
The visibility of rainbow depends on the size of water droplets in the air. The bigger the water drop, the brighter the rainbow, and the smaller the water drop, the less obvious the rainbow is.
Generally, in winter, the temperature is low, there are few water droplets in the air, and there are few opportunities for showers, so rainbows generally do not appear in winter.
Question 5: Why are there rainbows after a thunderstorm? After the rain clears, a semi-circular rainbow often appears in the sky, which is a light band composed of seven colors: red, orange, yellow, green, blue, indigo and purple. We call it a rainbow.
? The ancients in our country paid great attention to observing natural phenomena and had a scientific explanation for the rainbow in the sky a long time ago. Shen Kuo quoted Sun Yanguang as saying in Meng Qian Bi Tan: "Rainbow, rain shadow is in the middle of the sky, and rain is in the sun, so there is it." In Xuanzhenzi written by Zhang in the Tang Dynasty, it said: "Water sprays on the back of the sun to form a rainbow." It can be seen that the rainbow is formed by sunlight shining on water droplets in the air.
We know that when sunlight passes through a prism, it will disperse, and the original white light will be decomposed into seven colors: red, orange, yellow, green, blue, indigo and purple. Before or after the rain, there are many tiny water droplets suspended in the sky, which act as prisms. When the sun shines on water droplets, as shown in figure 1, it will happen once when they enter water droplets. Then, when the water drops shoot out, they are refracted again. These two refractions and reflections make colored light with different frequencies move in different directions, so dispersion occurs. Because sunlight is parallel light, only one direction emits the strongest light, and this direction is the direction in which we see the rainbow. The angle between this direction and the direction of incident sunlight is about 42 for red light, 40 for violet light and 40 for other colors. As shown in Figure 2, because there are many water drops in the sky, the rainbow can only be seen from the direction of the above angle, so the rainbow seen standing on the ground is semi-circular with ultraviolet red inside, as shown in Figure 3.
So why do rainbows often appear after rain in summer, but not in winter? Because there are often thunderstorms or showers in summer, the scope of these rains is not large. It often rains here, and the sky there is still sunny. After the rain, there are still many small drops of water hanging in the sky. In winter, the weather is generally cold, the air is dry, and there are fewer opportunities for rain, so there are fewer showers. Most of it is snowfall, and snowfall does not form rainbows, so rainbows rarely appear in winter.