Humidity of air – characteristic which expresses amount of the water vapor which is airborne. It is one of the most essential indicators describing weather and climate. In general, in the atmosphere of Earth the humidity changes over a wide range depending on height and a climatic zone.
Absolute humidity
The absolute humidity of air is the density of water vapor in air, otherwise, the mass of water vapor which actually holds in one cubic meter of air. The indicator is measured in grams on cubic meter.
Air is quite capable to reach a condition of full saturation, it occurs because at a constant temperature it is capable to absorb in itself(himself) only certain amount of steam. Such absolute humidity (when air is completely saturated) is called moisture capacity.
Relative humidity
The moisture capacity directly depends on temperature, and at its increase sharply increases. If to calculate the relation of absolute humidity of air at a concrete temperature to its moisture capacity at the same temperature, the indicator called relative humidity will turn out. If to analyze values of an indicator of relative humidity in Earth scales, then it is highest in equatorial to a zone, in polar latitudes and in continents of middle latitude in winter time, and is lowest in subtropical and tropical deserts. With increase in height the humidity of air quickly decreases.
How to learn relative humidity
The special device – the psychrometer is used to determination of value of relative air humidity. In fact it is a system from two thermometers. The gauze cover which tip is lowered in water is put on one of them. The second thermometer works in the usual mode and shows value of the current air temperature. The first, the thermometer with a cover, shows lower temperature (at evaporation of moisture from a cover heat is spent). The value of temperature which shows the moistened thermometer is called a cooling limit, and a difference between data dry and moistened – a psikhrometrichesky difference. At the same time relative air humidity is inversely proportional a psikhrometrichesky difference: the humidity, the more moisture is less air can absorb. For receiving a numerical indicator of relative humidity it is necessary to divide value of absolute humidity into the greatest possible humidity. Usually the result is expressed as a percentage. The indicator of humidity of air is very important, at too low or high humidity the health of the person worsens, the working capacity decreases, perception and memory worsens. Besides, at strictly certain limits of humidity of air it is required to store food, building materials and many electronic components.