What is the cause of drought in Yunnan?

Is southwest drought a natural factor or a man-made factor?

First of all, the severity of the drought is shocking.

From September 2009 to March 20 10, most areas in Yunnan, Guizhou, Sichuan, Chongqing and Guangxi suffered from drought with a recurrence period of 100. Drought lasts for a long time, affects a large area and involves a large population.

The author lives in Anshun City, the hinterland of Guizhou Province. From September last year to March 26th this year, it didn't rain for almost 240 days in Anshun. According to the meteorological department's standard of "continuous days without rain, more than 6 1 day in spring, more than 46 days in summer and more than 9 1 day in autumn and winter", the drought in most areas of Guizhou, such as Anshun, is among them.

The water in many reservoirs is reduced to one-half to one-third. The author went to a river with constant flowing water all the year round, and found that the long riverbed was like a paddy field. The silt in the riverbed was cracked, and some cracks were as wide as 3 ~ 4 cm. I walked along the river bank for a long time, and occasionally there was water in a river ditch. The shallow pond of 20 or 30 square meters has become the last water area for ducks raised by duck farmers to survive. Hundreds of ducks, less water and more ducks, and because the water doesn't flow, the color has already turned into thick ink, which is very unpleasant. If the drought continues, it will be difficult for ducks living in water to find even smelly ponds. Seeing such a scene makes people worry about the living conditions of these ducks, and then reminds them of how people who eat these ducks and duck eggs will feel and what impact they will have on their health.

At this time of last year, in the countryside, the leaves of rape in the fields are different in green and yellow, and the wheat seedlings are lush and full of spring everywhere. But this year, due to the lack of water, the farmland in high places is cracked and desolate, and there are twenty or thirty centimeters of rape flowers scattered in the farmland in low places. The desolate scene is like the winter season, which makes people feel distressed.

According to the media report on March 20th, 2065438+00, people in arid areas have a hard life and bathing has become a luxury. Some rural people pick wild vegetables to satisfy their hunger. While there is still no obvious rainfall in the heavy drought area in southwest China, the spring drought in North China will gradually appear and develop.

Looking at the fact that droughts have occurred one after another in China this year, it is getting better every year. Although the author is not a meteorologist, his concern makes him think about the cause of drought.

Second, meteorologists' analysis of the causes of drought did not touch the essence.

Recently, I read some meteorologists' analysis of the causes of drought in southwest China on the Internet and in newspapers. However, most of the analysis of the causes of drought is limited to the description of the phenomenon itself; A few analyses involving reasons always make people feel as if they have not talked about the essence of the problem. Of course, the author also knows that the weather forecast itself is difficult to be accurate so far, perhaps because domestic experts are ashamed to express their opinions.

Whether we can provide timely and accurate meteorological analysis for the public and relevant social departments at this critical moment of fighting drought is neither a simple meteorological academic issue nor a leisure topic that meteorologists talk about after dinner, but it is not only related to people's livelihood, but also to the overall situation of social stability.

This paper extracts the main viewpoints of two pairs of meteorologists from the country and a province, which are widely quoted by the media.

One is the plateau thermal factors of the Qinghai-Tibet Plateau, the other is the influence of El Ni? o phenomenon, and the third is the bad timing of cold air.

Second, the label "climate warming" should not be deducted casually. Drought is a continuous cumulative effect, and continuous lack of rain and high temperature are the direct causes of drought. Less precipitation in summer and autumn leads to dry water from rivers and insufficient water storage in reservoirs and ponds. At the same time, the continuous high temperature in autumn and winter leads to the intensification of soil moisture evaporation and promotes the development of drought.

It should be a layman's truth. I don't know what to say after reading the above two analyses. Now I analyze them as follows.

One said: the plateau thermal factor of the Qinghai-Tibet Plateau is that there was little snowfall on the Qinghai-Tibet Plateau last winter, which further affected the surrounding drought. However, for the general public to know the reasons for the decrease in snowfall on the Qinghai-Tibet Plateau last winter, experts did not talk about it, nor did they put forward their own views. Experts use the influence of El Nino phenomenon to explain the drought in southwest China (especially in Sichuan) this year, and think that there is less water vapor entering southwest China from the south. This conclusion seems to be one of the reasons if the occurrence of this drought coincides with the occurrence of El Ni? o this year. However, the author observed that in more than 200 days, there were more than 10 rain clouds passing through Anshun, but it was difficult to form rainfall. This phenomenon is hardly consistent with the expert's statement that a large amount of water vapor bypasses the dry area. In particular, the author still vaguely remembers the tragic situation of the historic drought that occurred in Chongqing in 2002 and 2006; In addition, Yunnan Province, which is located on the tropical edge, has experienced frequent droughts in recent years, and forest fires have continued year after year. It is really hard to believe that this drought is essentially related to the El Ni? o phenomenon that has occurred regularly for many years. Therefore, the author thinks that local meteorological problems should not only consider the influence of the general environment on local meteorology, but also consider the influence of the specific environment on local meteorology.

Experts said that the cold air did not grasp the opportunity to enter the inland, and then met with warm air in the inland to form rainfall. The author can't imagine the lifeless and thoughtless cold air flow, and how to ask it to seize the opportunity. If this statement is the imagination of experts on romantic occasions, there is nothing wrong with it. But it happened that experts answered the scientific questions raised by reporters on behalf of the people on very serious occasions.

Secondly, I said that "climate warming" can't be labeled casually. Drought is a persistent cumulative effect, and I agree with it very much. However, according to experts, the continuous lack of rain and high temperature are the direct causes of drought, and I think the expert's conclusion is that the ultimate cause of drought is not given. According to simple logic, as long as people in their right mind are eager to know what causes the problem of continuous low precipitation and high temperature. Only by understanding this essential problem can it be helpful for drought prevention in the future. Second, the direct reason given by experts does not reveal its relationship with human activities.

Judging from the current human bearing capacity, the continuous lack of rain and high temperature is a natural phenomenon that human resources are temporarily difficult to change-the occurrence and persistence of this drought is proof. Then, according to the conclusion given by experts, as long as there is a similar drought in the future, people will only have the fate of waiting, because it has nothing to do with human activities, and of course there is no need to change anything.

In addition, some people in the media think that the drought is caused by geological factors, which seems reasonable from the perspective of meteorological related factors. However, the author believes that although geological influence exists, it is a gradual process, and the accumulation of seismic energy can not be completed in about one year. Therefore, the drought caused by geological factors should be the characteristic of decreasing rainfall year by year, and it will never suddenly have little or no rainfall for such a long time.

As for some so-called experts who believe that drought is caused by excessive construction of reservoirs and power stations, the author thinks it is even more nonsense. Have you noticed that no matter how many reservoirs occupy, the area is limited compared with the vast surface (the author estimates that the area occupied by reservoirs is less than a dozen to a few tenths of the area of mountains and land). The water storage capacity on vast land should be several times that of the reservoir, and the ability to evaporate water vapor should be much greater than that of the reservoir. Readers can turn the land in the arid area of Yunnan and Guizhou in the TV picture into a gully with a crack width of several to 10 cm and a depth of 10 ~ 20 cm. You can know how much water the soil originally contained due to evaporation. Not to mention the vast paddy fields and the ability of many plants and trees to store water and evaporate water vapor.

In today's era, understanding meteorological problems is not only the needs of the general public for survival and production, but also the needs of governments at all levels and managers of related enterprises and institutions. Meteorologists can't say something without depth and guidance like a non-professional. Although I understand meteorological work and the difficulties of some experts, the purpose of taxpayers' support for meteorological experts is to get timely and effective guidance from experts when meteorological problems arise. I think this is the unshirkable responsibility and obligation of meteorologists, and this desire should not be excessive.

If experts can't make an accurate judgment on the cause of drought, and then guide the public to take active measures, it won't be long before the duck in front of today is our tomorrow.

Third, human factors should be the root cause of the persistent drought in various parts of China in recent years.

As a non-meteorological professional, although I dare not worry about the country and the people, I am concerned about the draft problem that everyone cares about. From the perspective of comprehensive disciplines and history, this paper puts forward the causes of drought in five provinces and cities in southwest China around 20 10 and the hypothesis of drought causes in many areas of China in recent years. To some extent, the occurrence of these droughts should be the inevitable result after the natural environment balance in these areas is broken by human activities, and it is an abnormal performance after the cumulative effect of human activities on meteorology reaches a critical point.

The reasons and arguments are as follows.

1, soil vegetation and water conservancy facilities are seriously damaged, and the water conservation ability is reduced.

In agricultural production, in order to pursue high yield, many farmers use a large number of pesticides such as chemical fertilizers and herbicides, and use land in a predatory manner, resulting in soil hardening, serious desertification and decreased water retention capacity. Under the same irrigation amount, the water holding period of farmland is obviously shortened. Burning wasteland and expanding farming will reduce the number of plants on the surface and weaken the ability to conserve water. The total amount of plants lost by deforestation exceeds the total amount of plants brought by artificial succession forests, and the effect of returning farmland to forests is not in place. The most important cause of drought is the weakening of water conservation ability caused by vegetation destruction.

Under the land contract system, the construction of farmland water conservancy has generally come to a standstill. For a long time, all localities have only used it without maintaining it, resulting in the abandonment of a large number of original water conservancy facilities, and the original water storage area has decreased year by year, losing its flood control and drought relief functions. In rainy spring and summer, a large amount of rainwater from the water falling from the sky quickly returns to the ocean through surface runoff. After the rainy season, in the absence of water conservancy construction, quite a few places fell into drought again.

2. The urban heat island effect is enhanced, and the surface temperature is on the rise.

In recent ten years, the degree of urbanization in China has increased rapidly. Whether in urban or rural areas, with the continuous growth of population, the continuous improvement of lifestyle and the continuous expansion of production scale, on the one hand, the emission of carbon dioxide has increased substantially, on the other hand, a large number of artificial floors and walls have appeared, making cities full of forests made of reinforced concrete, and there is a serious shortage of cooling materials such as urban green spaces and trees, which leads to the increase of surface temperature year by year and the continuous enhancement of surface heat radiation to the air. Urban fever is no exception in rural areas. Urban residents feel hot every year, which is largely related to the heat island effect. With the enhancement of urban heat island effect, the updraft over the town is strengthened, which increases the lifting ability of rain clouds and reduces rainfall.

3. The evaporation of water vapor decreases and the surface loses its self-cooling ability.

Due to the destruction of large areas of vegetation, poor soil water-holding capacity and greatly reduced water storage function of water conservancy facilities, the evaporation of water vapor brought by these factors has also decreased year by year. Rainfall caused by local water vapor evaporation will inevitably decrease. With the decrease of rainfall, the surface loses its self-cooling ability, resulting in the surface temperature only rising but not falling. For a long time, smog weather has decreased in both urban and rural areas. It is rare to see foggy weather in the sixties and seventies in cities for several years, which is an obvious example of the decrease of surface water vapor evaporation.

4. The desert formation effect makes it difficult for rain clouds in the past to rain, and the drought intensifies to form a vicious circle.

Desert experts believe that there are still many rain clouds passing through the desert every year, but because there is always an updraft above the desert, the rain clouds passing through it are always supported by the updraft to rain elsewhere, so that it is difficult for some deserts to rain for several years or even hundreds of years. Insufficient rainfall leads to further reduction of surface water vapor; Insufficient water vapor in turn reduces evaporation, making it difficult to form rain clouds and rain locally. No rainfall or little rainfall makes the desert temperature increase year by year, which intensifies the effect of lifting rain clouds and forms a vicious circle.

In the 240 days since September last year, there were many rain clouds floating over Anshun during the southwest drought. Even when the drought was very serious this spring, there were many rainy days, but rain clouds always came and went again and again, refusing to drop precious raindrops, even though the meteorological department made a lot of artificial rainfall efforts.

The author feels that the situation in Anshun and many arid areas seems to be a desert effect. On the one hand, due to its own soil erosion, the ability of water conservation in arid areas is weakened, so that there is little or no enough water vapor to form rainfall, thus losing its ability to cool itself. The surface temperature remains high for a long time, which makes the rain clouds floating over the arid land unable to rain. Without the cooling effect brought by rain, the surface temperature in arid areas will rise higher and higher, but the higher the temperature, the more difficult it is to have rain, and the drought for more than 200 days will continue under the influence of a vicious circle.

From a historical point of view, the disappearance of the ancient city of Loulan on the Silk Road may be due to the destruction of the environment, which accumulated year after year, making the water vapor around it decrease year by year, and finally reaching a certain critical value, making it more and more difficult for all localities to form rain clouds and cause rainfall. No rainfall or little rainfall leads to the increase of surface temperature in various places, which gradually leads to the increase of surface temperature and the decrease or even non-existence of rainfall, so that the ancient city of Loulan was eventually destroyed by the desert.

Looking at the recent drought in various parts of China, the author thinks that we should learn from the historical tragedy of the disappearance of Loulan ancient city.

The author hopes that people should face up to and fully understand the relationship between meteorological anomalies and human activities, and regard these droughts as warnings issued by nature after the meteorological balance is broken, so as to take targeted measures to respond positively.

4. The change of meteorological forecast accuracy proves that the influence of human activities on meteorology can not be ignored.

Some people may think that the author's above assumptions are groundless speculation. Then, the author invites readers to look at the changes in the accuracy of weather forecast again, and then we can know how much human activities have affected the weather.

When paying attention to the weather forecast, the public found that the accuracy of the weather forecast was very high for a period of time. However, in recent ten years, the weather forecast has been accurate in a large range, inaccurate in a small range, accurate in a long period and inaccurate in a short period.

It stands to reason that the overall academic qualifications of meteorological observation teams are getting higher and higher, and the observation facilities are getting more and more advanced. Why does the accuracy of its prediction decline instead of rising?

The author thinks that more than ten years ago, when meteorological satellites, computers and network systems were used in meteorological observation one after another, in order to adapt to the application of new scientific and technological means, the meteorological department designed a meteorological forecast model according to the actual situation in all parts of the country at that time. Based on the analysis of national satellite cloud pictures and their general trends, combined with local observation data, meteorological observation models are used for calculation and reasoning, and local forecast conclusions are drawn. Because the model designed at that time was more in line with the actual situation, the prediction accuracy was higher.

However, in recent ten years, with the rapid development of China's social economy, the landform changes with each passing day. Changes in landforms will inevitably lead to changes in related meteorology.

Someone once exaggeratedly said such a vivid example that a butterfly in South America fluttered there, and it won't take long to cause a storm in other states of the earth. From the perspective of system theory, it is reasonable. In theory, a butterfly can have such a far-reaching impact, not to mention the huge impact of long-term human activities that are much bigger than butterflies.

The landform is changing at any time, but the model used for weather forecast is not updated at any time. Therefore, it is reasonable that the prediction calculated by unrealistic model is inaccurate.

The reason why the large-area forecast is more accurate is inseparable from the satellite cloud images provided by meteorological satellites, the collection of meteorological data from all over the world by the Internet, and the rapid calculation by supercomputers. On a large scale, national and provincial meteorological forecasts can make up for and reduce the impact of local geomorphological changes because they occupy more observation data. Moreover, the large-scale forecast model is naturally more macroscopic than that of small areas, so the accuracy of meteorological forecast is closer to reality.

At present, the forecast of small areas is not accurate. As mentioned above, a small butterfly can cause or change the weather in distant areas, not to mention how earth-shaking changes have taken place in cities and rural areas.

In the city, have you noticed that with the acceleration of urban construction, a large number of high-rise buildings have sprung up in a year or even a few months; The height of the building is unprecedented, from dozens of stories to five or six stories short. The influence of architecture on wind power and direction is self-evident. The urban area is expanding day by day. In addition, high-grade highways, expressway and airports are constantly being built. The influence of these artificial floors and walls on urban temperature is also well known.

In rural areas, economic development has also brought obvious changes to rural vegetation. Land reclamation, road construction and bridge repair, village construction, mining and factory building, farming and forestry cultivation and other activities have also changed the rural natural landscape.

Changes in rural and urban landforms will inevitably have a great impact on meteorology. For the ever-changing urban and rural landforms, if the meteorological parameters of landforms that no longer exist are used to calculate the meteorological forecast, inaccuracy is an inevitable result. The reason why people have a more accurate feeling about the weather forecast is that the construction and development of various places in that period were far less rapid than now, and the speed of model design and modification was not high.

However, for the phenomenon that the current meteorological forecast is inaccurate, some meteorologists explained that meteorological technology has not yet reached the level of accurate forecast. Is that really the case? If the weather forecast can't accurately predict the situation in today's small areas, then the weather in smaller areas such as space launch bases and Olympic host cities should be unpredictable. In fact, not only such a small area can be predicted, but also the meteorological conditions that may appear in the designated area at a specific date and time, so that the relevant departments can decide the launch of the space shuttle and the holding time of the Olympic Games. At present, the phenomenon of inaccurate weather forecast in small areas, the author thinks that the problem of responsibility and input is more reflected here.

From the analysis of the change of weather forecast accuracy, it is enough to see that the scope and depth of human activities have reached an unprecedented level.

Verb (abbreviation of verb) Countermeasures and measures to eliminate man-made drought

To eliminate the drought caused by human factors, it is natural to reduce or stop the impact of these human factors on the natural environment and even the climate. The specific countermeasures are as follows.

1, do a good job in environmental protection and enhance the ability of vegetation to conserve water.

Do a good job in environmental protection and restore normal vegetation on the surface. Rural areas should change predatory farmland planting methods and pay attention to protecting the water storage capacity of soil and paddy fields. Try to use farmyard manure, keep farmland water and fertilizer, and reduce irrigation water consumption; Extend the storage period of farmland to increase the evaporation of more water vapor from farmland into the local air. Put an end to burning wasteland and ensure the water retention capacity of surface vegetation. By protecting the surface vegetation in rural areas, water resources can be conserved and the surface temperature in rural areas can be reduced.

2. Strengthen greening and reduce urban heat island effect.

Cities should plant trees in strict accordance with a certain proportion and reserve a certain amount of grassland. Some concrete floors of urban non-motor vehicle lanes should be paved with permeable materials as much as possible, and some walls should also be covered with vegetation to enhance water conservation and reduce the thermal radiation of concrete floors and walls to the atmosphere, thus effectively curbing the urban heat island effect. At the same time, by evaporating more water vapor from plants, urban humidity can be improved and urban heat island effect can be reduced.

3, the construction and maintenance of water conservancy facilities, play the role of drought and flood control of water conservancy facilities.

On the basis of scientific and rational planning, build new water conservancy facilities and expand the effective area of water conservancy facilities to resist floods and droughts as a whole; For the original water conservancy facilities, it is necessary to maintain the water storage area of water conservancy facilities, and increase the water storage capacity of these waters as much as possible to give full play to the drought and flood control functions of various water conservancy facilities. At the same time, it is necessary to ensure and increase the total amount of water vapor evaporation in various places, and use more water vapor evaporation to promote the formation of regional rain clouds and produce rainfall, thus reducing the local surface temperature, which is conducive to the rain clouds brought by the ocean monsoon to drop rain on the mainland.

4. Explore underground water sources and build a domestic drought-resistant water supply system.

In order to prevent unexpected drought from threatening people's survival, all localities should dig deep underground water sources and connect them with local water supply networks. However, these deep well water sources are not used at ordinary times. Only when there is a serious drought in various places can they be used to supply water to the victims in dry areas in time and conveniently, so as to ensure the basic needs of the victims in dry areas for domestic water.

To sum up, only by taking comprehensive and effective measures against the above countermeasures can all localities effectively change the regional water-saving problem, ensure the regional water vapor evaporation to return to the natural state, effectively reduce the regional surface warming phenomenon, thus creating a regional natural environment that conforms to natural laws and has good meteorological conditions, greatly enhancing the regional flood control and drought resistance, and creating a living environment that is harmonious with nature for the people in the region.