Those who have lived in villages for any length of time know that even on a summer morning, the grass is almost always wet from dew. But surely few people thought why this was happening. Where does this water come from, and what is the nature of this phenomenon in general?
What is the dew point?
Weather forecasts usually deal only with air temperature, precipitation, wind and atmospheric pressure. Meanwhile, there are many more important characteristics that give an idea of environmental conditions. Among them
is the dew point of the air. This term is familiar to many people, but not everyone knows what it is and what this indicator affects. So what is the dew point?
By this phrase is meant an indicator of air temperature at which the limit of its saturation with moisture is reached, as a result of which water begins to condense either in the form of water droplets on the surface or in the form of fog. Sometimes this does not really matter, and in some places this information must be taken into account.
Water vapor is always contained in the air in one way or another. And the dew point is a combination of certain factors in which there is a transition from a gaseous state of aggregation to liquid. In this case, condensation forms on objects with the lowest temperature, as well as on the lid of a pot with boiling water. Sometimes this causes problems, for example, residents of poorly insulated houses or owners of improperly installed double-glazed windows may encounter constant dampness and fogging of the glasses.
Education mechanism
So what happens when the temperature drops at night or in the early morning? That is, what is the dew point according to physics, and what processes occur when it is reached? Extremely interesting.
A thin layer of gas of the same temperature forms near the surface of the coldest objects. Its thickness can be scanty, but it is in it that condensation forms that precipitates on the surface of the object. On the street, it can primarily be stones, metal structures, grass. This happens if the air temperature is above the dew point. In winter, everything happens a little differently. This phenomenon can be observed when breathing in the cold, when steam comes out of the mouth. Cooling instantly, water in a gaseous state turns into tiny droplets. Something similar happens high in the atmosphere when clouds form.
Influence factors
But why is this happening? First of all, the formation of condensate is influenced by the temperature of the environment and objects. In addition, relative and absolute humidity is important. The higher these values, the higher the dew point temperature. At 100% humidity, this figure will coincide with the actual weather conditions.
Pressure is also important, first of all, if it is necessary to calculate the dew point temperature in compressed air. Physicists continue to conduct experiments in a variety of conditions. And in this case, the varieties of the atmospheric indicator are distinguished and it is under pressure. Other things being equal, the second indicator will be much lower.
Value calculation
So, now it has become clear what the dew point is, and what affects it. But how to calculate at what value of temperature and air humidity water vapor begins to condense? There are special tables and formulas with which you can calculate this indicator with a small error. The calculation of the dew point temperature by these methods takes into account only the
relative humidity of the air and its temperature, so that none of these methods is suitable for gases under pressure.
Of course, there are still special instruments that allow fixing this indicator - psychrometers. Their main purpose is to determine the air humidity, but they are also perfectly suitable for determining the dew point.
Value in construction
First of all, determining the dew point temperature is important in building design. Water has a detrimental effect on metals, because of it corrosion begins, so the formation of excess moisture can cause premature wear of the structure. If the temperature is high enough, the process will take place at a high speed.
It is also important for people for whom the problems of home insulation in winter are extremely relevant. In winter, the outside of the building is much colder than the inside. Thus, temperature differences are inevitable. And here it is important that the dew point in the wall is as far away as possible from the inner surface. Otherwise, residents are at risk of exposure to eternal humidity, dampness, mold and other consequences. So when building residential, both multi-unit and private, houses, this factor must be taken into account. The dew point in the wall will be reached in any case with a decrease in air temperature, but the task of the builders is to keep it as close to the outer layer as possible.
And all metal structures must be coated with special anti-corrosion compounds, as well as organize the effective removal of excess moisture from them. In the walls of houses, not only hygroscopic materials are used for this, but also special waterproofing materials. In the complex, this allows residents to not suffer because of forever wet and cold corners or window sills.
Importance in Aviation
Airplanes fly high in the air, where the temperature is lower than near the ground. And condensation can affect aerodynamics. This is especially important during takeoff and landing, therefore, among other environmental indicators, aeronautical meteorologists must also calculate the dew point. This helps to consider the possible formation of clouds and fog if the actual temperature is close to it. In winter, this information is also important, because in cold weather you need to think about the possible icing of the aircraft and prevent it with the help of special reagents that are applied to the hull of the aircraft.
Significance in other areas and countermeasures
In addition, manufacturers of varnishes, paints, and protective compounds also take this indicator into account. Naturally, manufacturers and users of high-precision optics should also keep this factor in mind so as not to harm the equipment, especially if you have to bring devices into a warm room from the street.
In order to avoid condensation inside buildings, it is necessary to provide good ventilation and proper moisture removal. For example, some people who want to save money may face the problem of constantly fogging or leaking windows. Poor or improperly installed double-glazed windows can become a source of constant problems. So it’s better to entrust such work to good professionals.
Microclimate and comfort
And what is the dew point for people? How do they feel under conditions when condensation forms? Here, relative humidity is of primary importance. At a sufficiently high temperature and an indicator of air saturation with water vapor, it seems to people that it is stuffy on the street or indoors. This is especially well felt by residents of the temperate climatic zone, arriving in the summer in the tropics or subtropics. With almost one hundred percent humidity, the dew point almost coincides with the actual air temperature, and people literally have nothing to breathe, especially if it is very hot. In such conditions, some may experience problems with the cardiovascular system, it is also possible to get a heat stroke, therefore, with a sharp deterioration in well-being, you must consult a doctor.