The causes of the 2010 drought in the southwest, the cause of the drought in the southwest

There are three main reasons for this severe drought in the southwest. The first is the influence of plateau thermal factors on the Qinghai-Tibet Plateau. The southwest provinces are greatly affected by the "roof of the world", the Qinghai-Tibet Plateau last winter had less snow, and the plateau thermal conditions were good, resulting in a weak Indo-Myanmar trough, a weak South Asian monsoon, and insufficient water vapor transported to the southwest of China.

The second is the impact of El Niño. Under this influence, the sea surface temperature in the eastern equatorial Pacific Ocean is warmer, the subtropical high is stronger overall, and the water vapor carried by the East Asian monsoon meets the cold air from the north to the south, resulting in more precipitation in the eastern part of China and frequent snowfall in the north. On the contrary, the southwest region of China is dominated by downdrafts, and there are often sunny and sunny weather.

Third, the timing of cold air has not been mastered. Although there have been several cold air impacts on our country this winter, most of the cold air has started to move eastward in the north. Coupled with the relationship between the Qinling Mountains, if the cold air is not "strong" enough to climb the mountain, it will still not be able to affect the basin, so it is difficult to form rainfall.

At the beginning of 2010, a violent cold wave and heavy snowfall not seen in decades hit most of northern China. At the same time, most of Yunnan is still sunny. In the past six months, Yunnan is experiencing a severe winter and spring drought situation due to a combination of factors such as abnormally low precipitation, abnormally low number of rainfall days, abnormally high temperature, and abnormally high evaporation, and the drought is expected to continue.

Why is there such a huge contrast in the same season? The main reason is that since June 2009, the sea water in the central and eastern equatorial Pacific Ocean has been abnormally warm, and a new "El Niño" event has occurred, which has caused abnormal atmospheric circulation, making it difficult for cold air from the north to move south to affect Yunnan, and the warm and humid airflow from the southwest of the Indian Ocean is weak, resulting in insufficient water vapor, coupled with the special geographical location of Yunnan's own low-latitude plateau, resulting in continuous drought last winter and this spring. Yunnan is a transitional intersection zone influenced by the circulation of multiple monsoons (East Asian monsoon, South Asian monsoon and plateau monsoon), and is a typical monsoon climate zone in China, with distinct dry and wet seasons.

The monsoon climate has formed the inevitability of drought disasters in Yunnan, and the unstable monsoon activities have caused the randomness of drought disasters in Yunnan. In recent years, under the background of global warming, drought in Yunnan has become more frequent and severe. The analysis shows that:

After the mid-to-late 80s of the 20th century, warming occurred in Yunnan, with the most obvious warming in the late 90s. Since 1986, there have been 13 years of warm winter, the number of frost days in winter and spring has decreased in most areas, the number of rainfall days in the province has gradually decreased, and the frequency of high temperature and drought events has increased, especially after entering the 21st century, high temperature and drought events have changed from once in 2 3 years to once in 1 2 years. The frequent occurrence of extreme weather and climate events has an increasingly severe impact on Yunnan's economic and social development.

Among them, the weather changes caused by climate warming have a very prominent impact on the drought situation in Yunnan. In particular, the average precipitation in Yunnan Province in 2009 was 29% lower than the multi-year average, breaking the record of the lowest precipitation in the same period since meteorological observation records began. The average maximum temperature in the province was the highest since meteorological records began; The average number of rainy days in the province broke the record for the fewest meteorological records. 91% of the stations in the province experienced severe drought; Seventy-three percent of the sites reached a particularly drought rating.

Yunnan is generally controlled by the straight, dry and warm westerly airflow in winter and spring, the weather is sunny and rainless, and the fire danger level of forests and urban and rural areas is significantly increased, especially the drought in late spring and early summer, which has a great impact on spring planting. To this end, it is necessary to make economical and rational use of the water stored in reservoirs and ponds to reduce the adverse impact of severe drought on industrial production and the livelihood of urban and rural people.

The southwest region due to the collision of tectonic plates. Causes the southwest to uplift. Formation of plateau areas. It is located in the inland and highland. Ocean precipitation is difficult to reach.

There are also the following aspects.

1) The karst landform in southwest China is extensive, and there are many karst caves and dark rivers underground, which is not conducive to water storage.

2) The southwest monsoon was weak and failed to reach the southwest of China;

3) The climate is arid in spring, the water vapor content in the air is small, the solid condensation nucleus is insufficient, and there are no conditions for the formation of precipitation'

4) There are many geological disasters in this area, with active plates and many faults, which is not conducive to the construction of large reservoirs, and the reserves of water resources are insufficient.

Since the beginning of autumn last year, there has been a severe drought in parts of southwestern China. On March 23, statistics from the National Defense General showed that the number of people who had difficulty drinking water due to drought had reached 22.71 million, of which 18.05 million were in the five provinces of Yunnan, Guizhou, Sichuan, Guizhou and Chongqing, where the drought was most severe. The area of cultivated land affected by drought was 11.4 billion mu, of which 96.54 million mu (85 percent) of cultivated land was affected by drought in the five southwestern provinces. The drought in southwest China is the most severe drought ever encountered since meteorological data were available, and the drought is characterized by a long duration, a large drought area, and a severe impact.

It is mainly due to complex ocean circulation and atmospheric circulation anomalies that have led to reduced precipitation and higher temperatures, resulting in persistent drought in southwest China. Precipitation in the southwest is mainly transported by water vapour from the Indian Ocean and the Bay of Bengal. However, there has been very little precipitation since last year, because the activity of the Indian (degree) and Burmese trough is very weak, which is not conducive to water vapor transport. In addition, since the autumn and winter of last year, the atmospheric circulation over the Qinghai-Tibet Plateau has begun to show obvious anomalies, and a tenacious cold and high-pressure air mass has formed in the plateau area, and the pressure field is strong, blocking the warm and humid air flow from the Indian Ocean and the Bay of Bengal. However, the cold air from the north does not reach the hinterland of the Yunnan-Guizhou Plateau in the southwest, and it is difficult for the cold and warm airflows to converge to form precipitation, so the precipitation is low, resulting in a much more severe drought than in previous years.

According to the data, Yunnan and Guizhou have been in a climate with less precipitation and higher temperature since the beginning of 2000, and there have been certain degrees of drought in recent years. There are two main conditions for the formation of drought: one is that the precipitation continues to be low, and the other is that the temperature is high.

Statistics from meteorological departments show that since September last year, the rainfall in most parts of Yunnan and Guizhou and some areas in Guangxi, Sichuan, and Chongqing has been more than 50 percent less than the same period for many years, and 7 to 90 percent less in some areas. The average temperature in Yunnan throughout the winter has reached the highest level since 1950. The direct cause of the drought in the southwest is also the lack of water during the rainy season.

Take Yunnan as an example: Yunnan can be roughly divided into two seasons every year, dry and wet, from November to April of the following year, because the cold high pressure on the Qinghai-Tibet Plateau will lead to a decrease in precipitation, these months are called the dry season in Yunnan. The wet season is from May to October every year, during which there is a lot of rain, and the precipitation gradually stopped after August last year, which is equivalent to the rainy season ended early, and in the following months, the temperature in Yunnan is higher than usual, and the precipitation has been less (compared with the same period in history, Yunnan and Guizhou are the least in history).

Many reservoirs in southwest China, such as Yunnan and Guizhou, rely mainly on rainfall during the rainy season to store water, and once this opportunity is missed, it is difficult for the reservoirs to replenish water. In the rainy season, there is little precipitation, little water storage, and high temperatures, which will inevitably lead to large evaporation and serious soil moisture loss.

The drought in southwest China this year has not shown signs of easing, what is the reason for such a long-term and widespread drought? Judging from the current situation, most climate experts believe that high temperature and lack of rain are the direct cause of drought, but what causes high temperature and lack of rain? There are many reasons for this.

Wang Jinsong, a researcher at the Lanzhou Institute of Arid Meteorology of the China Meteorological Administration, said that since June last year, the eastern Pacific Sea has been warming and is in an El Niño state, and this sea surface temperature anomaly affects the weakening of the Indian monsoon, leading to drought in the southwest. Since the beginning of autumn last year, the southwest airflow has been weak and the water vapor transport has led to less precipitation and higher temperature, which is the direct cause of the continuous meteorological drought in Yunnan and other places. "High temperatures and lack of rainfall are the most direct causes of drought in the southwest.

Wang Yongguang, chief forecaster of the National Climate Center, said in an interview that from the perspective of atmospheric circulation, since the beginning of winter, the southern branch trough has been weak, and the southwest warm and humid airflow from the Indian Ocean is relatively weak, resulting in insufficient water vapor, coupled with the lag in the response of the climate in the south to the El Niño phenomenon, the southwest region is prone to meteorological drought. Ma Zhenfeng, director of the Sichuan Provincial Climate Center, believes that Sichuan Province is greatly affected by the "roof of the world", and the Qinghai-Tibet Plateau had little snow last winter, and the plateau thermal factors are good, which affects the drought in the province. In addition, under the influence of the El Niño phenomenon, the heat flow on the surface of the Pacific Ocean goes eastward, carrying away tropical water vapor, resulting in more precipitation in the eastern part of China.

In contrast, tropical water vapour decreased, and water vapour from the south to the southwest also decreased. In recent years, drought has become the highest rate of meteorological disasters in China, the China Meteorological Administration released the "2009 Top Ten Weather and Climate Events", there are three events related to drought, namely "30 years of rare autumn and winter drought raids the northern winter wheat area", "50 years of the most serious spring drought plagues Heilongjiang, Inner Mongolia and other places", "50 years of rare autumn drought burns the southern land". At the beginning of this year, drought hit the southwest again.

Is there a common climatic cause behind some extreme weather phenomena, or is there a human factor at play? Gerald Mill, a senior scientist at the National Center for Atmospheric Research in the United States, said in an interview with this reporter that the climate itself contains many natural variables, such as droughts, floods, storms, and so on, which are all natural components of the climate system. Sometimes one can attribute part of the climate to naturally occurring phenomena, such as El Niño.

But Mir said that human-induced climate change is cumulative over a long period of time, and that a particular drought or storm cannot be absolutely attributed to human-induced climate change.

I believe that it is because of the mirror reflection of the water surface after the completion of the Three Gorges Dam, which reflects the sunlight into the atmosphere and increases the temperature of the atmosphere, so it cannot form a rain layer, so it does not rain for a long time.

Upstairs says that the surface of the water will reflect, then the snow-capped mountains will also reflect, and the Great Lakes of the United States will also reflect, why is there no such drought there? Will the water surface formed by the Three Gorges Dam be reflected? It doesn't seem to make sense!

Hello, the drought in the southwest has affected the harvest of corn, rice, peanuts, soybeans, potatoes and some other crops. Rice in southwest China is planted only once a year, and it is generally planted in March and April and harvested in September and October. The drought caused a large amount of water stored in the reservoirs to be used for rice planting and irrigation; The water in the rivers has dried up, and many farmlands have no water to irrigate.

You don't understand what you said about releasing water, but the time of irrigation is irregular, and if there is no water in the rice field, you have to irrigate, and you can't let it dry.

Harvests of maize and other crops have also been greatly affected. There is basically no harvest today.

It's useless to know that a drought is coming before the rice fields are dry. It is impossible to grow all drought-resistant crops, because of the influence of climate, soil quality, topography and other aspects, the disaster caused by drought is inevitable.

The main reasons for the drought in southwest China in 09 are: choose A, which is less affected by the warm airflow.

a, less affected by warm airflow b, less affected by plateau topography.

c, the winter monsoon is weak d, production, domestic water consumption increased sharply.

The main causes of drought in the southwest:

1. Influence of thermal factors on the Qinghai-Tibet Plateau: the winter of 2009 was characterized by abnormal atmospheric circulation, and the southwest provinces were mostly located in the southwest trough channel, the Qinghai-Tibet Plateau had less snow cover last winter, and the thermal conditions of the plateau were good, resulting in the weak Indo-Myanmar trough, the weak South Asian monsoon, and the insufficient water vapor transported to the southwest of China.

2. Natural geography and soil vegetation factors: the mountains in the area are undulating, the terrain is broken, the ravines are vertical and horizontal, the soil is poor, the most widely distributed soil is red soil, yellow soil, and lime soil, etc., this kind of soil itself is not drought tolerant, and in the mountainous areas with large terrain fluctuations, the soil is easy to be scoured, the water retention capacity is poor, and it is more susceptible to drought, and the karst mountainous area is the most vulnerable area. Due to population growth, deforestation and reclamation, and inappropriate farming practices, the area of soil erosion in southwest China has increased year by year, and the soil interception and storage of precipitation has decreased, which has exacerbated the occurrence of drought.

3. Insufficient water conservancy infrastructure: the drought has fully exposed the problem of weak water conservancy infrastructure, the population in the southwest region is scattered, and when encountering a major drought, the small water cellars on which the masses rely for survival are difficult to withstand the drought in the absence of water source supplements, and it is easy to have drinking water difficulties for people and livestock, which also highlights the importance of water conservancy infrastructure construction in the southwest region. In recent years, although the first level at all levels has increased investment in the construction of large-scale water source projects, the investment in small and medium-sized water source projects is limited.

Due to insufficient financial investment and the transfer of rural labor, many water conservancy facilities are aging and in disrepair, and the function of allocating water resources has deteriorated. In fact, small-scale water source projects and "five small" water conservancy projects in mountainous areas (small water cellars, small pools, small pumping stations, small ponds and dams, and small canals) are often the most direct projects to solve the benefits of agricultural irrigation and drinking water for people and livestock.

4. Uneven distribution of water resources: The demand for water resources for social and economic development has increased, and ecological damage and water pollution have exacerbated the prominence of this problem.