8 things you didn’t know about humidity

Solenco Reporter
 January 03, 2017
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It’s a hot summer’s day in Durban: 32 degrees with 75 percent humidity. We all know those numbers mean hot, but what exactly does that humidity percentage tell us? And why should we care? Below, some facts on humidity – 8 interesting facts in fact - and how it affects our daily lives:


1. Fifty percent humidity is a sponge half full.


Humidity describes the amount of water vapor or water molecules in the air. Weather scientists use the term “relative humidity,” which Joe Sobel, a meteorologist and senior vice president at Accuweather described as “a comparison of the amount of moisture in the air versus the amount of moisture the air could hold.”

Think of the atmosphere as a sponge that can hold a fixed amount of water, let’s say a litre of water. “If there is no water in the sponge… then the relative humidity would be zero,” Sobel said. Saturate the sponge with 500ml of water – half of what it is capable of holding – and that relative humidity climbs to 50 percent.

“The amount of moisture that the atmosphere can hold relates directly depends on the temperature,” Sobel said. Think of a rise in temperature like an increase in sponge size. A sponge that is half saturated with water is at 50 percent humidity. Now, increase the size of the sponge without adding more water. The relative humidity decreases because the bigger sponge is capable of taking on more moisture, but the same amount of water remains.

Soaking a sponge with more water than it can hold would cause it to drip. But this dripping doesn’t always symbolize rainfall. The relative humidity measured on the ground (where the sponge is) doesn’t reflect moisture levels kilometres above in the sky. Rain occurs when the rising air can no longer hold the water droplets that have formed clouds high in the sky. (Clouds can form closer to the ground too — that’s fog). The temperature and atmospheric pressure changes as you ascend into the sky — the air gets colder and thinner. So 100 percent humidity might not mean rain, but it does mean dew.

2. What’s the deal with dew?


Dew occurs when the relative humidity reaches 100 percent.

“Dew point temperature is an absolute measure of the amount of water vapour in the air,” Sobel said. If you have a dew point temperature of 65, that means that the outside temperature must decrease to 65 degrees before dew, or water, will form on your lawn. And if the temperature outside is 65 and the dew point is 65, then the relative humidity is 100 percent.

Dew point temperature is a good indicator of how comfortable or how uncomfortable you might feel, Sobel said. But we don’t hear about it on the Weather Channel. It does, however, get calculated into the “Real Feel” temperature along with other factors like wind, cloud cover and the angle of the sun.
3. Saudi Arabia has the highest recorded dew point temperature
Humidity comes from water evaporating from lakes and oceans. Warmer water evaporates more quickly – that’s why you find the most humid regions closer to warm bodies of water, like the Red Sea, the Persian Gulf, Indian Ocean and Miami. The highest dew point temperature ever recorded was 95 in July 2003, in Dhahran, Saudi Arabia.

4. Thank humidity for bad smells


Scientists in this 2008 study confirmed what many city dwellers already know — people are better at detecting smells in a humid environment. In heat and high humidity, there are more water molecules in the air to bind and carry odorous particles into our nose. Trash still smells in the winter, but the cold, dry air limits how far the stench can travel. This may also be what accounts for the dirty dog smell. As water molecules evaporate from soggy dog fur, they carry with them smelly bacteria.


5. Humidity brought us tonal language


Our vocal cords are comprised of a pair of mucus membranes that stretch across the voice box, or larynx. They vibrate, controlling the air from the lungs that flows by as we speak or sing. The level of moisture in the air affects the elasticity of our vocal cords. Singers can tell you that it is harder to carry a tune in a dry environment.

We’ve known for decades that you are more likely to be on pitch in humid environments. More recently, researchers theorized that speech was one of many human behaviours adapted to fit environment. After looking at more than 3,700 languages, they discovered that tonal languages, like Chinese and Vietnamese, rarely developed in dry climates.

6. Once upon a time, people measured humidity with hair curls


In 1783, Horace Bénédict de Saussure built the first hygrometer, a device to measure humidity, and he built it with… hair. To understand how it worked, you need to know a thing or two about hair.


A single strand of hair has many layers. The inner layer is filled with proteins called keratins that bind to each other, giving shape to your luscious locks. These proteins bind by forming tough disulphide bonds or weaker hydrogen bonds. You can thank hydrogen bonds for the funny way your hair dries naturally after getting out of the shower. Water molecules (two hydrogens and an oxygen) are soaked up by your hair and act as a bridge linking keratin molecules together in place. These hydrogen bonds keep your hair fixed in shape until you wet it again, allowing new hydrogen bonds to form.

In high humidity, water molecules in the air find their way into straight strands. As hydrogen bonds connect keratin proteins, hair starts to fold back on itself and curl. Frizzy fly-aways occur when hair folds back enough to break the cuticle – or the outer layer of hair that looks like dragon scales under a microscope.

The drier the hair, the more likely it is to soak up moisture in the atmosphere. So damaged hair – scorched by curling irons or parched from over shampooing – is often treated with moisturizing salon products.

Enter hygrometer. Saussure attached one end of a 10-inch piece of human hair to a screw. The rest of the strand he maneuvered through a pulley and attached to a weight. As the hair took on moisture, the strand curled and shortened moving the pulley and lifting the weight. Saussure could then calculate how much humidity was in the air based on how much the weight moved. The hair hygrometer can be made more sensitive by dipping the hair in alcohol and removing any oils that might prevent the strand from soaking up moisture.

7. With exercise and humidity — don’t overdo it


Even professional summer athletes have to adjust for changes in humidity. An important note about exercising in high humidity: it’s dangerous. “The higher the dew point, the less effectively you are going to cool after exercising,” Sobel said. And if you can’t cool yourself, your body can reach fatal temperatures.

Here’s why. When we exercise in hot temperatures, our bodies sweat to cool down. In dry air, the sweat evaporates quickly. But in humidity, sweat doesn’t evaporate as fast, and your body sweats more in an effort to keep cool. All that sweating dehydrates your body, leading you to overheat.
In the summer, our bodies actually take on extra water weight to account for the extra sweating.

8. Humidity is for the bugs, especially the moths


When it comes to wet heat in the insect world, it’s the little guy that thrives. Goggy Davidowitz, an entomologist at the University of Arizona explains that smaller insects, such as moths, flies and mosquitoes, are more likely to dehydrate because they have a larger surface area relative to their whole body size. Because most insects are small, and humidity increases survivorship, insects seek moist climates, Davidowitz said.

Control the humidity in your home, and have a look at our range of dehumidifiers.

For more information on how a dehumidifier can help, contact us today at info@solencosa.co.za or phone 0861 388 8681.

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