Atmospheric precipitation: what it is and how it is formed. Dew, frost, rain and snow are formed from the point of view of physics
The world around us is amazing. Mired in the routine of everyday life, we rarely notice it. However, it is a shame not to know how dew, frost, rain and snow are formed, because even schoolchildren know the answer to this question.
How does dew form in terms of physics?
The formation of water droplets in the morning on the grass and plants for a long time worried scientists. This question was dealt with by Aristotle. However, the ideas of scientists about this natural phenomenon up to the XVIII century was erroneous. Considering how the dew, frost, rain and snow are formed, the researchers thought that it was about the same. However, modern science tells us that this is far from the case. In order to figure out how dew forms, you first need to learn something about the air. And this important detail is that it contains a certain amount of moisture.And in the warm air it is more than in the cold. Therefore, in summer we can observe dew on the leaves of plants and grass. The air is in contact with the cold surface, which leads to condensation of a certain proportion of moisture contained in it. Moreover, the surface temperature must be below a certain value. It is called the "dew point." It depends on pressure and some other parameters.
Dew or not?
At home, you can spend, for example, such an experience. It is necessary to pour water into a glass or a metal vessel. Then you need to add ice to it. However, dew does not form immediately, but only when the vessel has cooled to a certain temperature. Similarly, in nature. Humid air comes in contact with a cold surface, which leads to the formation of dew droplets. The land and paths cool down significantly less than the plants, so they cannot be found on them. But not all that we see in the morning on leaves and grass is dew. The main part of moisture is emitted by the plants themselves. This process starts in the afternoon in order to protect the plants from the hot sun rays. In some areas of the Earth dew falls so much that it is used for watering animals.
This is another type of precipitation.To the question of how frost is formed, physics gives the following answer: in the process of desublimation, the gaseous substance (in this case water vapor) turns into a solid state. As we have said, moisture is initially present in the air. The trees were covered with frost due to the fact that during the thaw it evaporated, and then, when the temperature drops, everything freezes. The most suitable place for the formation of beautiful patterns is a rough surface with low conductivity of heat, for example, a wooden bench or open soil. Frost usually appears at night when there is a light breeze. It contributes to the fact that moisture during evaporation comes into contact with various surfaces. Too windy weather, on the contrary, prevents the appearance of needles of frost.
How does snow form in terms of physics?
Without this precipitation it is difficult to imagine winter in middle latitudes. Telling how dew, frost, rain and snow are formed, it is necessary to understand that the latter is ice crystals. They result from the freezing of water vapor. Clouds contain water droplets. When they freeze at low temperatures, small crystals of ice are formed. During the fall, they are glued to each other under the influence of the wind.This explains the beautiful shape of the snowflakes. Each of them always has six rays. The angles between them can be 60 or 120 degrees. Such accuracy is associated with the design features of the water molecule. Two identical snowflakes do not exist. The crunch, which we hear under our feet, passing along the snow-covered paths, is due to the breaking of the crystals that make up the flakes of this atmospheric sediment.
What is the color of the snow?
Children love to ask different questions about the world around them. Over time, people stop wondering around. However, answering the question “how are dew, hoarfrost, rain and snow formed”, one cannot but wonder why the latter seems to be exactly white, because the water is transparent. And here comes physics. We are surrounded by electromagnetic radiation, most of the waves of which are inaccessible to the naked human eye. The sun's rays contain a visible spectrum, that is, seven primary colors: purple, blue, blue, green, yellow, orange and red. If you merge them together, you get ... white. If the object absorbs light waves, then we see it in black. If he fully reflects them, then it is transparent.For example, this happens with ice or water. Orange is orange because it absorbs all colors except this one. Snow reflects the entire visible spectrum. Therefore, he sees us as white as the sunshine. Water and ice have a smoother structure, so they appear transparent. Considering how snow is formed, from the point of view of physics, one can understand that in its structure it consists of many water crystals, each of which reflects light at a different angle.
Why is it raining?
It is rather easy to explain this atmospheric phenomenon from the point of view of physics. The process itself is similar to the formation of snow, with the only difference being that it rains at a higher temperature. Water vapor evaporates and rushes to the clouds. At the height of the air temperature is much lower. Therefore, steam turns into ice crystals. Then falls under the force of gravity. During the flight of the crystals fall under the influence of warm air and defrost. When they reach the surface of the earth, they are already water droplets. They are called rain. Under the influence of wind flow clouds can be transported over long distances.Sometimes they travel thousands of kilometers. If in the way the clouds collide with each other, then they unite. When their mass becomes too high, it starts to rain. Interestingly, the drops have an identical shape. They differ only in size. There are drops that even reach six millimeters in diameter. When they collide with the ground, they are broken, creating many smaller ones. Most rains can be observed in regions with hot tropical climates.
Why do windows sweat?
There are several options for condensate. For example, it may appear only in the morning or only in the winter season. Separately, you need to consider the situation when water accumulates on the windowsill. Or the window in one room sweats, and in others it does not occur. The appearance of condensate is identical in nature to the process of dew formation, which we discussed at the beginning of the article.