How does dew form?
When I step out in the morning to fill the birdfeeder, I usually put on my rubber boots in order to keep my feet dry. Most mornings the grass is wet from all the dew that is clinging to the blades of grass. So how does dew form during the night?
Dew is actually water in the form of droplets. They are created by condensation that settles on exposed surfaces which cool by radiating heat. It condenses at a rate greater than it can evaporate. The water droplets form on grass, spider webs and other things in the early morning, but also at dusk.
Dew is actually water in the form of droplets. They are created by condensation that settles on exposed surfaces which cool by radiating heat. It condenses at a rate greater than it can evaporate. The water droplets form on grass, spider webs and other things in the early morning, but also at dusk.
The air around us contains water which we call humidity. Hot air can absorb more moisture than cold air. During the night, when temperatures drop, the cool air is getting denser and cannot hold all the moisture. The moisture it accommodated during the warm day will condense into the water droplets that then settle on the exposed surfaces. outside.
I remember once being embarrassed when I offered one evening to help a friend paint the hull of a boat he was renovating. He looked at me scornfully and pointed out that the dew fall that evening would ruin the paint job! This had never occurred to me.
You can watch the formation of dew with this small demonstration. Take a glass and put ice cold water in it and perhaps add some ice cubes. In no time, on the outside of the glass, condensation will appear and eventually water drops will slide down and “dew” has formed.
When there are no clouds during the evening and during the night, the warm air will radiate into space and the dew formation is more substantial. On cloudy nights when the warm air is trapped near the surface, there is no dew or very little.
I remember once being embarrassed when I offered one evening to help a friend paint the hull of a boat he was renovating. He looked at me scornfully and pointed out that the dew fall that evening would ruin the paint job! This had never occurred to me.
You can watch the formation of dew with this small demonstration. Take a glass and put ice cold water in it and perhaps add some ice cubes. In no time, on the outside of the glass, condensation will appear and eventually water drops will slide down and “dew” has formed.
When there are no clouds during the evening and during the night, the warm air will radiate into space and the dew formation is more substantial. On cloudy nights when the warm air is trapped near the surface, there is no dew or very little.
If the temperature gets cold enough in the evening, dew may undergo another transformation, dew may freeze to a solid form that is called “frost” If the surfaces like twigs, blades of grass or fences are already at sub freezing levels, then water molecules will jump directly from the gas state to solid state in a process known as “deposition”, and “hoar-frost” will form. In the presence of a light breeze, pretty dramatic formations can form. Frozen water droplets on bushes look very pretty, but frozen droplets on the windshield need to be scraped off!
Hoarfrost on barbed wire
In Germany you have a special word for the frozen dew: “Reif”. It means that the humidity in the air freezes. We all have seen it, for example on the wings of airplanes. They have to be de-iced before the plane can take off. A buildup of ice (or snow) on the wings, horizontal stabilizers, and vertical stabilizer not only add extra weight, but most importantly, they also disrupt the flow of air, which reduces lift. It can also disrupt the movement of the wings' flaps and ailerons, which are a part of an airplane wing that can be moved up and down to cause the airplane to turn, rise or descend. Deicing fluid, a mixture of a chemical called glycol and water, is generally heated and sprayed under pressure to remove ice and snow on the aircraft. While it removes ice (and snow), deicing fluid has a limited ability to prevent further ice from forming. So if the plane is delayed too long on the ground, it may have to be deiced again.
Walking with bare feet on grass which is saturated with dew, is considered a very healthy sport in Germany. According to Sebastian Kneipp, who was born in 1812, it gives you the necessary kick for the day, but also strengthens your immune system and your leg muscles. Kneipp, the “water doctor”, believed in the water cure and encouraged people to use it for the healing effect. I’m not sure if it is a cure, but it is quite invigorating!
Dew is important in some areas. Certain species of plants depend on dew. For example, in areas that have lengthy dry seasons, such as deserts, plants and pine seedlings depend on dew to survive. For many desert creatures, the dewfall may be their only source of water. Indeed, there is a lizard that lives in Africa’s Kalahari desert, whose only source of water is dew. Each morning, as the sun warms the land and forms rising thermals of air, it positions itself at the crest of a dune facing the sea. The warm, humid air being pulled in from the sea coats it in dew and is enough to sustain it.
I am always surprised how nature helps all creatures to fill their needs.
I am always surprised how nature helps all creatures to fill their needs.
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