At the heart of emergence of many natural processes and the phenomena – a rain, snow, hoarfrost, fog, dew – lie surprising physical property of water. Dew is the droplets of water appearing on vegetation at the summer nights and disappearing under sunshine in the morning. There is such turn of speech: "dew dropped out". Really, to some extent dew – a type of an atmospheric precipitation. However, it does not drop out as, for example, a rain or snow of a cloud, and, strictly speaking, it - not absolutely, and not only atmospheric water. And what then?
Instruction
1. Process of evaporation of moisture from any water surface happens constantly. Some percent of water evaporates also from the soil. Under the influence of sunshine the evaporation happens more intensively. Microscopic droplets form steam, transparent streams rising above the ground. Air masses always contain water vapor, but in its warm air it is more.
2. But there comes evening, the sun sets, and the Earth's surface begins to cool down slowly. If the sky star and cloudless, the Earth's surface is cooled quicker. The warm layers of air containing water vapor adjoin to the objects which are quickly giving heat and too are cooled. It is noticed – dew is not formed on the earth as it long keeps day heat.
3. Air masses, gradually adjacent to the earth, are cooled up to the temperature called a dew point. At this temperature of couples becomes saturated and it is condensed on cold objects – a grass, leaves. Formation of dew is promoted by the easy breeze which is carrying away the air masses which already gave a part of the water vapor and bringing new saturated with moisture. And here early in the morning on a grass and leaves trees dewdrops appear.
4. Water vapor contains in air always, but quantity it in different areas of the earth variously. Respectively, also degree of intensity of formation of dew is various. For example, in its deserts drops out very little, but it is very important as it is almost only source of moisture for all live.
5. Most intensively process of formation of dew happens in tropics. High daytime temperatures in these areas very promote moisture evaporation therefore near-earth layers of air contain a large amount of water vapor. In hot equatorial areas day and night almost do not differ on time therefore in a night the earth's surface manages to cool down quite strongly. Especially quickly heat is given by violent tropical vegetation. All these factors lead to intensive condensation of water vapor.
6. It is noticed, however, that on dew vegetation in the morning it is always more, than on not live objects – colored benches, roofs, stones, fences, etc. Scientists found out that only a small part of the moisture appearing early in the morning on a grass and leaves of plants is condensate. The most part of morning dew – result of process of a self-irrigation, self-irrigation t.e. Through tiny an ustyitsa from a plant organism on a surface droplets of the water arriving from roots act. Thus the plant saves itself during a summer heat from the scorching beams of the sun.