Doesn't mean it will rain.

Humidity is a physical quantity used to describe the water vapor content in the air. There are many ways to express air humidity, among which the most commonly used is "relative humidity" in meteorology.

Then what is relative humidity? Let's think of air as a sponge. It can hold a certain amount of water at most, such as 1 liter. Then the relative humidity refers to the ratio of the actual water content (absolute humidity) of the sponge to the maximum water content. If the sponge does not absorb water, then the relative humidity is zero; If the sponge drinks 500 ml of water, the relative humidity is 50%.

The maximum amount of water vapor that the atmosphere can hold mainly depends on the temperature. An increase in temperature is equivalent to a larger sponge that can hold more water. Therefore, when the size of the sponge increases without adding more water, the relative humidity will decrease.

If the sponge is filled with water and continues to add water, the excess water vapor will precipitate. But that doesn't mean it will rain. Because the relative humidity is usually measured on the ground, it can't accurately reflect the humidity at high altitude.

Even when the humidity in the upper air is saturated and the excess water vapor condenses into small water droplets, these small water droplets will not immediately fall into the rain as in a sponge saturated with water. Because they are light and small (most of them are only 0.0 1~0.02 mm in diameter), they are supported by rising air and form floating clouds. Only when the water drops keep absorbing water and gaining weight until the air can't hold it, will they fall and become Mao Mao rain.

So 100% humidity doesn't mean it will rain.

2. The higher the dew point, the more uncomfortable people are.

But when the humidity reaches 100%, dew will definitely appear.

When the water vapor content is constant, the temperature decreases, which is equivalent to the sponge becoming smaller, and finally the water vapor in the air reaches saturation. As a result, excess water vapor is separated and turned into dew.

When water vapor in the air condenses to form dew point, it is called ambient temperature. For example, the dew point is 18℃, which means that the outside temperature must drop below 18℃ before the water vapor in the air can reach saturation, forming shiny droplets on grass and leaves.

Dew point is a method to measure absolute humidity. For example, if the dew point of a place is 12℃, then the absolute humidity of the air here is the saturated water vapor at 12℃.

Therefore, the higher the dew point, the more water vapor in the air. When there is a lot of water vapor, the temperature or relative humidity is generally higher. After all, the bigger the sponge, the more water it can hold. The fuller the sponge, the more water it can hold. Conversely, the lower the dew point, the less water vapor in the air. There are two situations when there is little water vapor. First, the temperature is low, that is, the sponge is small and the water holding capacity is not large; Second, the relative humidity is low, that is, although the sponge is large, it absorbs less water.

Although the weather forecast does not mention dew point, dew point is actually an important indicator to measure whether the body feels comfortable or not. Coupled with factors such as wind and sunshine, it affects our somatosensory temperature (that is, the air temperature that the human body feels realistic).

When the dew point is high, people usually feel uncomfortable. Because as mentioned above, the temperature is generally higher at high dew point, which will make people sweat. High dew point is sometimes accompanied by high relative humidity, which hinders sweat evaporation, and people will feel uncomfortable or even get sick because of high body temperature. When the dew point is low, the temperature or relative humidity will be lower, both of which can effectively radiate heat from the body, so it is more comfortable.

The water vapor in the air mainly comes from the evaporation of oceans and lakes. The higher the water temperature, the faster the water evaporates, and the more water vapor in the air. Therefore, most of the high dew point areas on earth are close to warm waters, such as Persian Gulf, Red Sea and Gulf of Aden, which are the three areas with the highest dew point in the world.

The Persian Gulf is the region with the highest water temperature on the earth, and its summer water temperature can reach 30~33℃. Therefore, the highest dew point on record in the world-35℃ (3: 00 pm on July 8, 2003) appeared in Dharam on the west coast of the Persian Gulf.

This city stinks in summer.

Have you found that the city is more smelly in summer, and there will be bursts of odor in the air from time to time. Why is this?

In addition to the fact that garbage in summer is more prone to corruption, scientists have also found that people's sense of smell is more sensitive in a humid environment. This is because high temperature and high humidity make more water molecules float in the air, and the movement speed is accelerated. A large number of active water molecules bring more smelly particles into our noses, so cities in summer stink even more.

This can also explain why the wet "soup dog" smells worse. There are many bacteria, yeast and other microorganisms in dog hair, which will produce some unpleasant compounds. After the dog gets wet, these smelly substances will be brought into our noses by evaporated water molecules, making the dog's smell worse.

You can smell the stench of garbage in winter, but the cold and dry air will limit the travel distance of odor particles and greatly reduce their killing range.

4. The air is dry, and singing is easy to go out of tune.

Our vocal cords are composed of a pair of symmetrical mucous membranes. When vocalizing, the airflow of trachea and lungs constantly impacts the vocal cords, making them vibrate and vocalize. Vocal cords control the tone of our speech or singing by controlling the airflow. Interestingly, in a dry environment, it is difficult to sing without losing tune.

In fact, researchers speculate that humidity gives language rich tones. After counting more than 3,700 languages in the world, they found that languages with complex tones, such as Cantonese, Vietnamese and many African languages, are more likely to appear in humid areas of the earth.

Studies show that most languages with complex tones are located in tropical areas of Southeast Asia and Africa, and a few are located in humid areas of North America, Amazon Basin and New Guinea. For example, various European languages, including English, generally appear in drier places-cold north or dry desert, not tonal language.

The reason for this interesting pattern is that the humidity of the air will affect the elasticity of the vocal cords. There is a fixed proportion of water and polysaccharide in the mucus layer on the surface of vocal cords to keep the mucus layer soft and elastic, which is the key to sound production. Inhalation of dry air will dehydrate the vocal cords, resulting in an increase in viscosity and a decrease in elasticity of the mucus layer, making it difficult to produce complex tones.

5. You can measure the humidity of your hair.

If you have long hair, you may not have to worry that the weather forecast will tell you the humidity of the air. Because hair is sensitive to humidity, when the air is humid, straight hair will bend and curly hair will curl more. Swiss physicist Saussure also discovered this interesting phenomenon, and then he made the world's first hair hygrometer out of hair.

Southall fixed one end of a bundle of 25.4 cm long hair on a screw, and the other end passed through a pulley and connected to a heavy object. Hair will become shorter when it is wetted by water, which will drive heavy objects to move upwards. Southall calculates the humidity of the air according to the distance the weight moves.

Why does hair become shorter after absorbing water?

The main component of hair is a kind of protein called keratin. As we all know, protein is composed of amino acids, which are long peptide chains arranged hand in hand. As shown in the above figure, through disulfide bonds or hydrogen bonds, peptide chains can form a spiral structure and further fold.

Disulfide bond is very stable, it is not affected by humidity, as long as you don't have a perm, it can almost last forever. This gives our hair strength and toughness. Hydrogen bond is weak, sensitive to humidity, and can be interrupted and reconstructed at any time.

When wet, there are more water molecules in the air, which means that hydrogen bonds can be formed between adjacent amino acids, and more hydrogen bonds can be formed between amino acids located in different positions and between different peptide chains, which will make the peptide chains constantly fold and bend. However, when the humidity decreases, many hydrogen bonds will break, and the peptide chain will be stretched again and become longer. Its macro performance is that with the increase of humidity, hair becomes shorter.

If you think of your hair as a spring, blowing it dry is equivalent to straightening and lengthening the spring. When wet, a large number of hydrogen bonds will further Bai Wan, fold or even entangle the spring, and the hair will become shorter.

Although the hair hygrometer is very rough, even you can do it yourself at home, it was not until the 1960s that the hair hygrometer retired from the historical stage and was replaced by an electronic hygrometer.

It is dangerous to exercise when the weather is hot and humid.

Even professional athletes must adjust the amount of exercise according to the change of humidity.

Baseball is a sport greatly influenced by humidity. If the player can't adjust the hitting intensity according to the field, then every 20% increase in relative humidity will produce a home run. The most direct way is to hit the ball directly outside the home run wall 90 ~ 100 meters away, so that the farther the baseball is played, the better. ) will be reduced by about 25%.

When the humidity of the stadium is high, baseball will absorb water and gain weight, which will lead to the decrease of hitting speed; Moreover, the resistance of the ball in humid air will be greater, and under the influence of both, the distance of baseball flight will be shorter. Every time the flying distance of the ball is reduced by 1m, the probability of hitting a home run will be reduced by about 7.5%. Therefore, it is easier for players to hit home runs at high altitudes, because the humidity there is lower and the ball flies farther.

In fact, strenuous exercise in high humidity environment is very dangerous. Because when we exercise in a hot environment, our bodies will sweat to cool down. If the air is dry, sweat can evaporate quickly, take away the heat on the body surface and effectively lower the body temperature. But if the humidity is high, sweat is difficult to evaporate, and the body has to sweat more to try to lower the body temperature. Excessive sweating can lead to dehydration, and if it is not treated in time, people are prone to heatstroke.

So when it is hot and humid, you'd better reduce the time of outdoor exercise and replenish water in time after exercise.

7. Humidity tells moths where there is more nectar.

The hot and humid environment we hate is like heaven for insects.

Compared with large animals, insects are more prone to dehydration because their relative surface area (the ratio of body surface area to volume) is larger, which means that more water will be lost by transpiration from the body surface. As we know, most insects are very small, and high humidity will increase their survival rate, so most insects are sensitive to humidity and always like wet paradise. Among them, moths are the most important, which can detect humidity changes as small as 4%.

In addition, moths can find their food-nectar by detecting the change of humidity.

Nectar has transpiration, and the relative humidity above the head of newly blooming flowers will be about 4% higher than the environment. Then the humidity difference will gradually decrease until the nectar is exhausted after about half an hour. In other words, half an hour later, the flowers may still be in full bloom, but the nectar is gone. Moths can only enjoy nectar if they find flowers that bloom for less than half an hour. Therefore, the keen perception of humidity changes can help moths quickly judge which flowers have more nectar.

This article comes from the article of "The Mystery of Big Science and Technology * Science", No.2016. Readers are welcome to pay attention to the micro signal of our big technology: hdkj 1997.