What are the strange phenomena in the desert?

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[Problem-solving process]

The climate of the desert has many characteristics, such as many sunny days, strong sunlight, dryness, hot summers, large temperature differences between day and night, lots of wind and sand, etc. The key is "dry". Because it is dry, there are less clouds and rain, more sunshine, and stronger sunlight; because it is dry, there are no clouds in the sky, which cannot block part of the sunlight, and there is no moisture on the ground, so it cannot evaporate and cool down. All the heat from the sun reaching the ground is used to heat the earth and the air. The temperature in summer is extremely high, and the temperature difference between day and night is extremely large; because it is dry, there are few ground plants, and the wind blows sand.

In the desert area, sometimes the sky is covered with dark clouds, the wind roars, and dazzling lightning flashes. It seems that a thunderstorm is coming, but often after waiting for a long time, I look at the clouds again. It's all gone, but the raindrops haven't fallen yet. In fact, it is definitely raining in the sky, but it is just because the air is too dry. The raindrops evaporate halfway through the thick dry atmosphere before they fall to the ground!

In the desert, due to the strong sunlight, dry air, and very few bacteria in the air, even the carcasses of camels and other animals did not rot and shriveled up to become mummies. It is said that when the Central Asian Turkmen cut their fingers, they grabbed some sand that had been "sterilized" in the sun and sprinkled it on the wound, and it soon healed. The dry climate in the desert is also very beneficial for the treatment of nephritis, because in hot and arid climates, the skin sweats more, which can reduce the work of the kidneys, allowing them to recuperate better. In Cairo, the capital of Egypt with a desert climate, there is a sanatorium that specializes in treating nephritis.

Many people have heard the story that eggs can be roasted in the desert without a fire. Some people think this is a joke, but it is actually true. In the summer, place the eggs on the sand, sprinkle a thin layer of sand on top, and the eggs can be baked in less than an hour. And according to everyone's preference, the eggs can be baked older or tenderer, but the baking time is different.

According to reports, a camel roving medical team of the Lanzhou Army of the People's Liberation Army took out the hot sand around noon, put the cake in, covered it with sand, and put dry wood such as camel thorns on top. , after the dry firewood is burned, the sand is peeled off, and there are sheets of browned green onion pancakes!

The four seasons in the desert are also very different from other places at the same latitude. In eastern my country, due to the monsoon continental climate, the spring and autumn seasons are inherently short. In desert areas, however, spring and autumn are shorter. Because the desert area is too dry, there is no moisture regulation. The temperature rises sharply in spring and plummets in autumn. The total length of spring and autumn lasts only about two and a half to three months. When the spring and autumn seasons are short, the winter and summer seasons are extremely long, so some people describe it as: "In the arid areas of Central Asia, there are only two seasons a year: winter in Siberia and summer in the Sahara." This makes sense. Temperature changes in desert climates are the most extreme among various climates in the world.

Strange desert climate

The climate of the desert has many characteristics, such as many sunny days, strong sunshine, dryness, hot summers, large temperature differences between day and night, lots of wind and sand, etc. The key is "dry". Because it is dry, there are less clouds and rain, more sunshine, and stronger sunlight; because it is dry, there are no clouds in the sky, which cannot block part of the sunlight, and there is no moisture on the ground, so it cannot evaporate and cool down. All the heat from the sun reaching the ground is used to heat the earth and the air. The temperature in summer is extremely high, and the temperature difference between day and night is extremely large; because it is dry, there are few plants on the ground, and the wind blows sand.

How far does it go in the desert?

In my country's desert areas, the annual rainfall is mostly below 50-100 mm, with the least amount being only 10-20 mm. Turpan, which is rich in raisins and cantaloupe, has an annual rainfall of only 16.4 mm. The rainfall in Toksun County is even less, even only 6.9 millimeters. This amount of rainfall is not enough to evaporate in a day in the desert. Talking about rainy days, Turpan only has 15.0 rainy days on average every year, and Toksun has less than 10 days on average. Most of them are light rains that can only wet the ground. The rain on August 14, 1958 was 36 millimeters, which was considered the heaviest since the founding of the People's Republic of China. In the desert area, sometimes the sky is covered with dark clouds, the wind roars, and dazzling lightning flashes. It seems that a thunderstorm is coming, but often after waiting for a long time, the clouds have dispersed and the raindrops have not yet come. Come down. In fact, it is indeed raining in the sky, but because the air is too dry, the raindrops evaporate halfway through the thick dry atmosphere before they fall to the ground.

This situation is called "rain flag" in meteorology. In the past, ordinary people didn't know the reason and called it "devil rain".

However, because the surface temperature in the desert is extremely high and the up and down convection of the air is extremely strong, extremely large raindrops can sometimes be generated in the clouds. These raindrops will not evaporate completely along the way and can still fall to the ground. But the raindrops of this kind of rain are very sparse. A geographer joked that if a person could always stay between the raindrops, he could walk in the rain without getting his clothes wet.

Meteorological departments often use relative humidity to measure the amount of water vapor in the air. A relative humidity of 100% means the air is saturated. The average relative humidity in desert areas is only about 20%, and can often fall below 10% in the afternoon. Sometimes, 0% records are found in meteorological records. In other words, there is no more water vapor in the air, at least it cannot be detected by instruments. When washing clothes in summer when the relative humidity is very low, if you wash them one piece at a time, generally speaking, by the time you wash the third piece, the first piece will be dry and ready to wear.

How high is the temperature on the ground at noon in the desert? In our country, records of 70℃ are not uncommon. The highest scale of the ground thermometer in Turpan is 75°C, but the mercury column has far exceeded 75°C on several occasions. On the surface of the sand dunes in the southern Turpan Basin, 82.3°C was once measured.

The high temperature during the day in the desert is due to strong solar radiation. The sun shines for more than 3,000 hours every year in desert areas. In the most places, it can exceed 3,600 hours. In the Sahara Desert, it can even exceed 4,000 hours. In other words, the sun must shine for more than 10 hours every day. However, once the sun sets, there are no clouds and fog in the atmosphere, very little water vapor, and the ground cools and dissipates heat very quickly. Therefore, the diurnal temperature range in arid desert areas is particularly large. In the summer half year, on average, the difference between the highest temperature in the afternoon and the lowest temperature in the morning is about 15℃ to 16℃. For example, the average minimum temperature in Turpan in July is 25.1℃, and the average maximum temperature is 39.9℃, a difference of 14.8℃. In September, the average maximum temperature in Turpan in the afternoon is 27.5℃, and can often exceed 30℃, but the average minimum temperature in the early morning is only 9.3℃. , it can drop to 0℃ to 5℃ on some days. Therefore, the Turpan Basin has a saying of "wearing fur coats in the morning and wearing gauze in the afternoon".

In many Gobi deserts in the world, due to the scorching sun, the rocks crack and often make a shooting-like sound. Some people call it the "sound of the sun." This is because the temperature of the desert climate varies greatly between days, and the surface of the stone that is already cool at night is strongly heated after the sun rises, causing the stone to expand unevenly inside and out and crack. Over time, the rocks eventually turn into sand.

According to records, in the Qilian Mountains of my country, people used to crush rocks with their hands, blow the sand with the wind, and select gold. Under the attack of nature's cold and heat, the hardest granite finally fell into pieces.

The high temperature on the desert surface causes a huge temperature difference between the upper and lower layers of the air layer. The temperature distribution of cool air at the top and hot at the bottom can reflect distant scenery in front and below the traveler. In meteorology, it is called a mirage, commonly known as a mirage. Therefore, travelers in the desert often see blue lakes in front of them. In fact, it is a reflection of the sky in the distance, which makes them happy in vain. On the black asphalt road in the summer afternoon, we can often see a pool of blue water on the road ahead. When we get closer, it disappears and moves to the front again. This is also a scam where mirages appear up and down the road.

The four seasons in the desert are also very different from other places at the same latitude. The eastern part of my country has a monsoon continental climate, so the spring and autumn seasons are inherently short. However, in desert areas, spring and autumn are shorter. Because the desert area is too dry, there is no moisture regulation. In spring, the temperature rises sharply, and in autumn, the temperature plummets. The total length of spring and autumn only lasts about 2 and a half to 3 months. When spring and autumn are short, winter and summer are extremely long, so some people describe it as: "In the arid areas of Central Asia, there are only two seasons a year: winter in Siberia and summer in the Sahara." This makes sense. Temperature changes in desert climates are the most extreme among various climates in the world.