Dew

Source: Wikipedia, the free encyclopedia.
Not to be confused with Guttation, the process by which plants release excess water from the tips of their leaves.
For other uses, see Dew (disambiguation).
A dewdrop on a clover
A drop of dew in the middle of a clover
Dew formed on the surface of strawberry leaves
A drop of dew on a Colocasia leaf at the Garden Society of Gothenburg
Dew drops on a flower
Dense dew on grass
Under cold temperatures, dew may freeze and form a layer of ice over plants and objects.

Dew is

droplets that appears on thin, exposed objects in the morning or evening due to condensation.[1]

As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets.[2]

When temperatures are low enough, dew takes the form of ice, called frost.

Because dew is related to the temperature of surfaces, in late summer it forms most easily on surfaces that are not warmed by conducted heat from deep ground, such as grass, leaves, railings, car roofs, and bridges.

Formation

Water vapor will condense into droplets depending on the temperature. The

clouds. The thermodynamic principles of formation, however, are the same. Dew is commonly formed during select times of the day. Nights, early mornings, and early evenings are all times during which dew is likely to be found.[4]

Occurrence

Adequate cooling of the surface typically takes place when it loses more energy by

thermal conductivity restricts the replacement of such losses from deeper ground layers, which are typically warmer at night.[3] Preferred objects of dew formation are thus poor conducting or well isolated from the ground, and non-metallic, while shiny metal coated surfaces are poor infrared radiators. Preferred weather conditions include the absence of clouds and little water vapor in the higher atmosphere to minimize greenhouse effects and sufficient humidity of the air near the ground. Typical dew nights are classically considered calm, because the wind transports (nocturnally) warmer air from higher levels to the cold surface. However, if the atmosphere is the major source of moisture (this type is called dewfall), a certain amount of ventilation is needed to replace the vapor that is already condensed. The highest optimum wind speeds could be found on arid islands. Wind always seems adverse, however, if the wet soil beneath is the major source of vapor (in which case dew is said to form by distillation
).

The processes of dew formation do not restrict its occurrence to the night and the outdoors. They are also working when eyeglasses get steamy in a warm, wet room or in industrial processes. However, the term condensation is preferred in these cases.

Measurement

A classical device for dew measurement is the drosometer. A small (artificial) condenser surface is suspended from an arm attached to a pointer or a pen that records the weight changes of the condenser on a drum. Besides being very wind sensitive, however, this, like all artificial surface devices, only provides a measure of the meteorological potential for dew formation. The actual amount of dew in a specific place is strongly dependent on surface properties. For its measurement, plants, leaves, or whole soil columns are placed on a balance with their surface at the same height and in the same surroundings as would occur naturally, thus providing a small lysimeter. Further methods include estimation by means of comparing the droplets to standardized photographs or volumetric measurement of the amount of water wiped from the surface. Some of these methods include guttation, while others only measure dewfall and/or distillation.

Significance

Due to its dependence on

Atacama and Namib deserts, however, is mostly attributed to fog water. In the Negev Desert in Israel, dew has been found to account for almost half of the water found in three dominant desert species: Salsola inermis, Artemisia sieberi and Haloxylon scoparium.[5]

Another effect of dew is its hydration of fungal substrates and the mycelia of species such as pleated inkcaps, often found on lawns, and Phytophthora infestans which causes blight on potato plants.[6]

Historic

The book

hoar-frost is congealed dew, and 'dew-frost' is dew which is half congealed".[7]

In Greek mythology, Ersa is the goddess and personification of dew. Also, according to the myth, the dew in the morning was created when

her son
's death, although later he received immortality.

Dew, known in

Avital.[9][10]

In the Biblical Torah or Old Testament, dew is used symbolically in Deuteronomy 32:2: "My doctrine shall drop as the rain, my speech shall distill as the dew, as the small rain upon the tender herb, and as the showers upon the grass."[11]

In the Catholic Mass in the Western Rite, whenever the Second Eucharistic Prayer is used, the priest prays over bread and wine, to God the Father; ‘Make holy, therefore, these gifts, we pray, by sending down your Spirit upon them like the dewfall, so that they may become for us the Body and Blood of our Lord Jesus Christ.’ The idea that the Holy Spirit enters the world and our lives in a quiet, undramatic way, ‘like the dewfall’, has great appeal for many Christians.

Artificial harvesting

Main article: Air well (condenser)

The

International Organization for Dew Utilization
(OPUR) is working on effective, foil-based condensers for regions where rain or fog cannot cover water needs throughout the year.

Large-scale dew harvesting systems have been made by the

Kutch[12]
.These condensers can harvest more than 200 liters (on average) of dew water per night for about 90 nights in the October-to-May dew season. The IIMA research laboratory has shown that dew can serve as a supplementary source of water in coastal arid areas.

A large-scale dew harvesting scheme envisages circulating cold sea water in EPDM collectors near the seashore. These condense dew and fog to supply clean drinking water.[13] Other, more recent, studies display possible roof integration for dew harvesting devices.[14]

References

  1. ^ "dew". Merriam-Webster.com Dictionary.
  2. The Columbia Encyclopedia
     (6th ed.). Retrieved 18 May 2013.
  3. ^ a b "Dew and Frost Development". ZHU Training Page. National Weather Service, NOAA. Retrieved 2021-10-21.
  4. hdl:10125/8818/
    .
  5. S2CID 18134058
    .
  6. ^ "Late Blight in Potato — Publications". www.ag.ndsu.edu. 5 May 2017. Retrieved 2021-10-21.
  7. ^ Aristotle; Forster, E. S.; Dobson, J. F. (1914). De Mundo. p. End of chapter 3.
  8. Jewish Encyclopedia
    . Retrieved 21 Dec 2008.
  9. ISBN 978-0-19-861060-1
    . Retrieved 2018-11-17.
  10. ^ "Abital". Retrieved 2013-06-27.
  11. ^ Deuteronomy 32: King James Version, accessed 22 September 2019
  12. ISSN 0022-1694
    .
  13. doi:10.1016/S0011-9164(00)88647-6
    .
  14. doi:10.2166/aqua.2018.174
    .

External links

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