Hygroscopy

The hygroscopy characterizes the relative Humidité of the Air, namely the proportion of Steam which it contains. It does not take into account the Eau present in form solid Liquide or .

In Meteorology, it belongs to the principal raised and modelled quantities. It is measured with a Hygromètre or a thermohygrometer (because temperature and hygroscopy are two interdependent parameters to some extent).

General information

The tables which summarize the properties Physique S and Thermodynamique S of the air pay to the dry air, i.e. in the absence of any steam. Indeed,

the hygroscopy is variable in space and time, on a a few hour scale even less (for example when it rains or when the dew is formed) and non-uniform on a hundred scale of meters, even sometimes of the meter so that it is impossible to define standard properties of the ambient air. The moisture of the air is mainly influenced by the quantity of water available, the Température and the Running S atmospheric.

the properties of the Humid air can strongly deviate about it, because the proportion of steam can reach up to 4% in volume under usual weather conditions; the bearing pressure of the air, the transport of the light, the odors, certain molecules (whose certain perfumes, Hormone S), the range of the sounds, the transparency of the air, acidity and air pollution, the Halation S or the luminous Pollution, etc are thus affected by the hygroscopy. The steam is besides one of most important gases with Greenhouse effect.
the evaporation of the water of the Ocean S, the River S and the Cloud S, the Wind as well as the vegetable Perspiration and the evapotranspiration are sources of increase or regulation of the Hygrométrie. In nature, all these factors depend for whole or part on solar energy and the alive one. In medium anthropized or confined (house, car, work place) the water-steam one expired by the man, the water emitted by the chimneys and the mufflers become determining to explain the variations of hygroscopy. For lack of vegetable evapotranspiration, the urban air of the dense cities is abnormally dry. Paradoxically with the top of the sea or a lake, even in tropical zone air perhaps much drier than under the Canopée. In the desert the air is extremely dry the day, but can be wet the night.
a fall of temperature tends to increase the hygroscopy because the Steam pressure saturating with the cold air is lower than that of the hot air.
the airstreams bring moisture in the zones (upper atmosphere, dry areas).
Of the materials (plaster, wood.), or of the phenomena (evapotranspiration, ground wind/wind of sea, formation of dew and its evaporation (to level, to control) the variations of the hygroscopy plug.

In natural environment, the Dew and the very fast appearance of Moisissure S on the dead organic matter are indicators of high relative moisture.

In confined surroundings a high hygrometrical rate supports the allergies or pathologies induced by the presence of acarina and spores of moulds. It is one of the elements of the phenomenon known as of interior Pollution. Conversely a too low hygroscopy is factor of desydratation of the also harmful mucous membranes and dust contamination to health.

See too

Simple: Humidity Zh-yue: 濕度

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