The Taklimakan Desert is getting wetter! Why is rainfall in southern Xinjiang becoming more frequent?

On August 27, the topic #新疆塔克拉玛干漠发Flood# ranked first in the Weibo hot search. When people mention the Taklimakan Desert, they think of water shortage, drought, little rain or even no rain. Therefore, many netizens were very surprised to see floods in such a dry desert, which sparked heated discussions.

The flood occurred near the Azhele Service Area of ​​the Taklimakan Desert Station on the Ahe Desert Highway. Some netizens even said humorously: It has become the Taklimakan "wet" desert! Why does the desert flood?

The Ahe Desert Highway is a graded highway built along the Hotan River that runs through the Taklimakan Desert. So where does the water in the desert come from? Why does this surprising situation occur? Netizens have given their own reasons.

Some people believe that this is due to the seasonal rise in the water level of the Hotan River. The Hotan River originates from the Karakoram Mountains and the Kunlun Mountains and flows northward into the Tarim Basin. If the snow and glaciers in the Kunlun Mountains melt faster due to continued high temperatures, the flow rate of the Hotan River out of the mountains will increase significantly, forming floods, and it is not uncommon for some of the water to flow into the desert.

Others have given this analysis: The terrain in the southern mountainous areas of Hotan is steep and the mountains are exposed. Once a short-term heavy rainfall occurs, the rainwater will infiltrate less and the surface runoff will be fast, so floods are easy to form. If they encounter snowmelt floods from upstream, the two flood peaks will overlap and the power will be particularly strong. This reminds people of the rainfall from August 22 to 23: Kashgar Prefecture, Kezhou Mountain Area, Aksu Prefecture, the southern mountainous areas of Hotan Prefecture, and the northern mountainous areas of Bayingolin Mongol Autonomous Prefecture all experienced moderate to heavy rains.

In general, netizens' opinions can be summarized as follows: floods in the desert are the result of the superposition of high-temperature melt water and heavy rainfall in the mountains.

In fact, this is not the first time that floods have been found in the Taklimakan Desert. The Tarim River and its source tributaries, including the Hotan River, the Yarkand River and other rivers, often have snowmelt floods that overflow the river channel and appear in the desert. The larger one was in July 2021. The flood occurred in the border area between Kuqa City and Luntai County, located in the lower reaches of the Erbatai River, which temporarily became a "water town". On that occasion, the explanation given by meteorological experts was: heavy rains hit the western part of southern Xinjiang, and the superposition of melted snow water from the Tianshan Mountains in summer formed seasonal floods that flowed into the desert.

It seems that the cause of that desert flood is basically consistent with the analysis of netizens on this flood.

Is the Taklimakan Desert becoming increasingly " wet "?

The Taklimakan Desert in the Tarim Basin is far from the sea, so it is blocked by moist air currents and has a dry climate. Annual precipitation is generally less than 50 mm, and there is very little precipitation, especially in the depths of the desert. However, its average evaporation is as high as 2500-3400 mm. The temperature on the desert surface can reach 70 to 80 degrees Celsius during the day.

The high temperature and high evaporation in summer make it difficult to associate the Taklimakan Desert with "wetness". However, in recent years, rain has visited southern Xinjiang more and more frequently, often wetting this "dry" sea.

Just looking at this summer, there have been frequent rainfalls in southern Xinjiang, which in turn "moistened" parts of the Taklimakan Desert.

In addition to the recent heavy rainfall, from August 6 to 8, parts of southern Kashgar, Hotan, Aksu, Bayingolin Mongol Autonomous Prefecture and other places also experienced heavy rains, accompanied by short-term heavy rainfall in some areas; on July 20 and 21, parts of western southern Xinjiang and other places experienced rainfall, among which parts of Aksu Prefecture and other places experienced moderate to heavy rain; from July 4 to 6, parts of western southern Xinjiang and other places experienced heavy to torrential rains; on May 27, the heart of the Taklimakan Desert in Bayingolin Mongol Autonomous Prefecture ushered in a rainfall...

Frequent rainfall has made many people feel that southern Xinjiang is getting more and more humid, and that "the Taklimakan Desert has entered a rainy season." This has also been partially confirmed by the data.

According to data from the Xinjiang Meteorological Bureau, in July this year, the average precipitation in southern Xinjiang was 46% higher than normal, and in the western mountainous areas of southern Xinjiang and other areas it was more than 50% higher.

Data from the China Meteorological Administration show that due to the impact of global warming, Xinjiang has become the most sensitive and significant region in the country in terms of "warming and humidification", with the largest increase in summer precipitation, with the number of rainstorm days and rainfall increasing by about 12% every 10 years on average. Areas with more precipitation than usual are mainly concentrated in Kashgar, Kezhou, and the western and northern parts of Aksu in the western part of southern Xinjiang.

On July 22 this year, He Miao, who was verified as the vice chairman of the Bayingol Federation of Industry and Commerce, talked about his personal experience on his personal Weibo: It has been raining continuously recently, and it feels like the Taklimakan Desert has also had a rainy season, which was unimaginable before. Korla is located on the northeastern edge of the Taklimakan Desert, with little rainfall, less than 60 mm per year, and is very dry. In recent years, the rainfall in the Tarim Basin in southern Xinjiang has generally increased, and Korla has also experienced continuous rainfall. A few days ago, the rainfall in Puhui Township, Korla reached 28 mm in one hour, which can be called a rainstorm!

Why is rainfall in southern Xinjiang becoming more frequent?

Why is rainfall in southern Xinjiang becoming more frequent? An expert from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences once said: Affected by global climate change, Xinjiang has shown a certain warming and humidification phenomenon in the past 40 years. As the temperature rises, the annual precipitation also increases significantly, and floods occasionally occur.

Some experts analyzed that the rainfall in southern Xinjiang is affected by the Siberian swamp airflow. The Siberian airflow goes south along the gap between Alashankou and Tianshan Mountain and enters the Tarim Basin. Due to the high temperature in the Tarim region in the early stage, the warm and humid airflow continues to rise. When it encounters the surrounding mountains, it forms a large-scale heavy rainfall. Just like boiling water, the water is constantly heated, but it is blocked by the pot wall, and the hot air can only continue to rise. When it reaches a certain height, the temperature drops and the hot air condenses into water droplets. This shows that the local temperature in Siberia is much higher and the swamp has thawed on a large scale, which is consistent with global warming.

Why can't water seep into the desert?

Many netizens are wondering, the desert is full of sand, so why can't water seep in and even form floods?

In fact, extremely dry desert conditions are ideal for flooding because the sand in the desert does not absorb rainwater quickly.

Let's first understand the desert floor. The wind and intermittent rain in the Taklimakan Desert gradually remove sand, dust and other fine particles, leaving behind larger fragments of particles to form the desert floor. The larger fragments of particles left behind are shaken into place by the forces of rain, running water, wind, gravity, creep, thermal expansion and contraction, wetting and drying, frost expansion, and the earth's constant micro-seismic earthquakes, eventually forming a layer of desert floor as hard as concrete. When rainfall occurs, the extremely dry desert floor prevents the absorption of rainwater. As a result, rainwater and melted glacier water remain on the ground, are concentrated by the terrain and flow to low-lying areas, forming the desert floods that people see.

In the short term, increased precipitation is beneficial to the restoration of desert vegetation ecology. Some netizens happily speculated: With frequent rainfall, will the Taklimakan Desert become an oasis one day? Experts gave this explanation: Although there is a trend of increasing precipitation in southern Xinjiang, the interannual variation is large. Compared with evaporation, its precipitation is far from reaching a balance between income and expenditure. It cannot be used as a long-term measurement standard, nor is it enough to change the pattern of extreme drought in the desert. Therefore, the conjecture of turning the desert into an oasis is not realistic.

(Some materials come from: China Meteorological Bureau, Xinjiang Meteorological Bureau, Xinhua News Agency, Xinjiang Daily, China Meteorological Science Popularization, Geography Teaching and Research Alliance Source: Pomegranate Cloud/Xinjiang Daily Comprehensive)