Causes and characteristics of tropical desert climate

The tropical desert climate is distributed in the mainland or the west coast between the Tropic of Cancer and 30 degrees north and south latitude, and extends to inland areas, such as northern Africa, Arabian Peninsula in Asia and desert areas in Australia.

The climatic reasons are as follows: firstly, it is controlled by the subtropical high. Subtropical high is a kind of dynamic high, which is a warm high because the air flow over the equator continuously accumulates over the subtropical zone, resulting in downward air flow, which leads to the increase of low-altitude air pressure. The subtropical weather is sunny and dry, mainly because of the prevailing downdraft.

Second, it is controlled by the dry trade wind. Trade winds are directional winds blowing from subtropical high to equatorial low. Due to the rotation of the earth, the wind direction in the northern hemisphere shifts to the right and becomes the northeast trade wind. It turns left in the southern hemisphere and becomes the southeast trade wind. In the subtropical region of the northern hemisphere, the west coast of the mainland is on the leeward side of the northeast trade wind, and the east coast of the mainland is on the windward side of the northeast trade wind. Similarly, in the subtropical region of the southern hemisphere, the west coast of the mainland is on the leeward side of the southeast trade wind, and the east coast of the mainland is on the windward side of the southeast trade wind. In this way, there is little precipitation on the west coast of subtropical areas in the northern and southern hemispheres, with dry climate and desert; But there is more precipitation on the east coast of the mainland, not a desert.

Third, affected by the cold current. Ocean currents have a great influence on the climate. Cold current can reduce the temperature and humidity of the area it flows through, while warm current can increase the temperature and humidity of the area it flows through. From the world climate and ocean current map, it can be seen that the west coast of subtropical continent is affected by cold current, with scarce precipitation and dry climate; The east coast of the mainland is affected by the warm current, and there is more precipitation. As for the formation of tropical desert climate in subtropical areas, it is not only affected by subtropical high or dry trade winds, but also related to being far away from the ocean and being less affected by the ocean.

Climatic characteristics Desert climate has many characteristics, such as sunny days, strong sunshine, dryness, hot summer, large temperature difference between day and night, and many sandstorms.

The key is "doing". Because it is dry, there is less rain, more sunshine and strong sunshine; Because it is dry, there is no cloud in the sky, so it can't stop some sunshine, and there is no water on the ground, so it can't evaporate and cool down. All the heat from the sun on the ground is used to heat the earth and the air, so the temperature in summer is particularly high, and the temperature difference between day and night is particularly large. Because of the dry weather, there are few plants on the ground. When there is wind, it will blow sand.

The high temperature on the desert surface makes the temperature difference between the upper and lower atmosphere close to the ground extremely large. However, the temperature distribution of cold air layer and hot air layer can reflect the distant scenery in front of travelers, which is called a mirage in meteorology, commonly known as a mirage. Therefore, travelers in the desert often see a blue lake in front of them. In fact, it is the reflection of the distant sky that makes them happy. On the black asphalt pavement in summer afternoon, you can often see a piece of blue water on the road ahead. When you take a closer look, it disappears and moves to the front. This is also a mirage scam on the road.

The four seasons in the desert are also very different from other places at the same latitude. In the east of China, the spring and autumn seasons are very short because of the monsoon climate. However, in desert areas, spring and autumn are shorter. Because the desert area is too dry, there is no water regulation. The temperature rises in a straight line in spring and falls in autumn. The sum of spring and autumn is only about two and a half months to three months.

Spring and autumn are short, and winter and summer are particularly long, so some people describe it as: "In the arid areas of Central Asia, there are only two seasons in a year: winter in Siberia and summer in the Sahara." There is some truth in this statement. The temperature change of desert climate is the most extreme among all kinds of climate in the world.