Fifteen-day weather forecast in Tuzuoqi

Click on June 6, 2005: 154 times Source: China Meteorological News.

Drought refers to disasters such as crop death and insufficient drinking water for people and livestock caused by long sunshine, little rain or little rain, soil water shortage and air drying. Considering the weather conditions, drought also includes dry hot wind, high temperature and heat wave. Drought is the most serious meteorological disaster of agriculture in China, and the losses caused are quite serious. According to relevant statistics, the average drought-affected area of crops in China is more than 300 million mu, and the affected area is 65.438+0.2 billion mu. The average annual output reduction due to drought is 654.38+000-654.38+05 billion kg, and the annual economic loss caused by water shortage is 200 billion yuan. Drought disaster has the characteristics of large area, obvious seasonality, strong persistence, strong regional and latent, and great interannual change.

Drought disaster prevention

South-to-North Water Transfer Project: The construction of the South-to-North Water Transfer Project will lead the Yangtze River water to the north, which can fundamentally solve the drought problem in the north;

Building water conservancy and scientific irrigation: in agricultural production, attention should be paid to building water conservancy and reservoirs, which is not only beneficial to flood control, but also to drought resistance. In areas where droughts often occur, it is particularly important to popularize water-saving irrigation technology and develop irrigated agriculture by using reservoirs.

Vegetation construction: returning farmland to forests and greening the environment are important methods to prevent drought;

Pay attention to the forecast of drought disasters: China's meteorological departments have always regarded drought and other meteorological disasters as the main content of monitoring and forecasting. Therefore, we should attach importance to meteorological forecast, make full use of this important information, make good drought-resistant decisions and take measures to alleviate drought disasters;

Artificial precipitation enhancement: Artificial precipitation enhancement is an active measure for drought resistance and disaster reduction. The method is to sow the catalyst in the cloud with rainfall conditions, so that the cloud will rain early. As early as 1958, China carried out research and experiments on weather modification. At present, many provinces (autonomous regions and municipalities) have carried out artificial precipitation enhancement operations, gained a lot of valuable experience and achieved remarkable results;

Interception and storage of rain fog: There are many ways to intercept and store rain, such as building small reservoirs on mountains, building small and low retaining dams and large water cellars in ponds and valleys, and building water storage cellars and rain collection cellars on hillsides. You can use the method of "casting a net" to collect fog, which is more suitable for foggy mountainous areas and rural areas;

Popularize drought-tolerant varieties and drought-resistant sowing methods;

No-tillage method: No-tillage method can be used for farming in arid and water-deficient areas to reduce soil erosion.

drought

From a natural point of view, drought and drought are two different scientific concepts. Drought usually refers to a climatic phenomenon that the total amount of fresh water is not enough to meet people's survival and economic development. Drought is generally a long-term phenomenon, but drought is different. Only occasional natural disasters, even in areas rich in water resources, will be caused by temporary climate anomalies. Drought and drought are the main natural disasters faced by human beings since ancient times. Even today when science and technology are so advanced, their disastrous consequences still abound. It is particularly noteworthy that with the development of human economy and population expansion, the shortage of water resources is becoming more and more serious, which directly leads to the expansion of drought area and the aggravation of drought. The drought trend has become a global concern. The twentieth century is coming to an end, and mankind is about to enter a new era. In the face of the increasingly serious global drought trend, it is necessary to explore the causes and find countermeasures.

Development, utilization and protection of climate resources in arid areas of northwest China

The arid area in northwest China accounts for about 30% of the total land area and 3.8% of the national population. Administratively, it includes all of Xinjiang Uygur Autonomous Region, most of Inner Mongolia Autonomous Region (except Daxinganling Mountain in the north of Hulunbeier League), Ningxia Hui Autonomous Region (except Liupanshan Mountain), Hexi Corridor in Gansu Province and Bashang area in Hebei Province.

The arid geographical environment in northwest China was first formed in the Late Cretaceous and the Early Tertiary, and then experienced Himalayan orogeny and the uplift of the Qinghai-Tibet Plateau, and the drought degree became more intense, gradually forming the existing special geographical environment.

In this vast land, there are abundant natural resources such as land, minerals, solar energy and wind energy, as well as some water resources and biological resources. For thousands of years, people of all ethnic groups have extensively developed and utilized and established many fertile farmland and rich pastures. The land here is vast and sparsely populated, and the level of industrial and agricultural production is low. Desolate and barren sandy deserts (deserts) and stony deserts (Gobi) are widely distributed, and natural disasters such as drought, salinity and sandstorm are serious. In this fragile ecological environment, unreasonable land use can easily lead to land degradation and productivity reduction.

The climatic characteristics of arid areas in northwest China are mainly characterized by drought and little rain, drastic changes in cold and summer, heavy sandstorm and strong solar radiation. The annual precipitation is generally below 400 mm, and decreases with the increase of the distance from the sea from east to west (except in western Xinjiang). East of Zuo Qi-Bailing Temple-Etuoke Banner-Yanchi Line in Su Nite, the annual precipitation is generally 300-400 mm, and the dryness is 1.5-2.0, which belongs to semi-arid area. Natural vegetation is mainly dry grassland, which has been the best in China since ancient times. It is also possible to carry out dry farming reluctantly, but the "nine droughts in ten years" make the output unstable and easy to form serious desertification problems. Between this line and Helan Mountain, the annual precipitation is 200 ~ 300mm, and the dryness is 2.0 ~ 4.0. Natural vegetation is mainly desert grassland, so irrigation is necessary for agriculture. In the vast desert area west of Helan Mountain, the annual precipitation is less than 200mm and the dryness is greater than 4.0. Crops must be irrigated more than 3 ~ 4 times a year, and trees and grass need to be watered many times.

The precipitation variability in this area is very large, and it often does not drop for several months to more than half a year, especially in the early spring and the "stuck neck" drought in April, May and early June. However, in one or two days in summer and autumn, it can reduce the annual total rainfall of 1/2 or even 2/3 of the rainstorm, and sometimes even cause floods.

Due to drought and lack of rain, solar energy resources are very rich. The sunshine in the whole year generally reaches 2500 ~ 3000 hours, and the Xingxingxia Valley adjacent to Gansu and Xinjiang reaches 3549 hours. Generally, the solar radiation reaches 54× 108 ~ 63× 108 Joule/m2 year, which is beneficial to the growth and development of crops and pastures and creates favorable conditions for the extensive use of solar energy.

Judging from the temperature conditions, the Tarim Basin and the southwest of Hexi Corridor belong to the warm temperate zone, with the accumulated temperature above 4000 ~ 4500℃ during ≥ 10℃ and the frost-free period above 200 ~ 220 days. Crops can be harvested twice a year or three times in two years, and crops with high economic value such as long-staple cotton, melons and fruits can be planted. Other vast areas belong to temperate zone ≥ 10. Due to the prevalence of continental climate, cold and summer changes dramatically. The average temperature in northern Xinjiang and Leng Yue, Inner Mongolia (1 month) is generally around -20℃, and the extreme minimum temperature in Fuyun (altitude 1 177 m) is -5 1.5℃, while Turpan (altitude-15) is not far away. In addition, on the surface of the vast desert Gobi, the temperature can reach above 50 ~ 60℃ at noon in summer and autumn, and optical phenomena such as mirage are common, which is obviously unfavorable to plant growth and human life.

Too much wind and sand is also one of the main natural transformation problems in the arid area of northwest China. In spring and autumn, due to the violent intersection of cold and warm air currents, it is warm and cold at first, and it is stormy. In summer, the vertical airflow is strong, with "hot east wind" and "burning wind" at the foot of the mountain. Coupled with the dry climate, wide ground, sparse vegetation, rich sand sources and other reasons, sandstorms often occur in most areas and most of the time, especially near the mountain pass and in the center of the desert and Gobi. For example, in Minqin City surrounded by Tengger Desert, the average number of sandstorm days is 133.5 days. Anxi City, surrounded by the Gobi Desert, has an average windy day of 38.8 days for many years and is known as the "World Wind Bank". Another "landwind warehouse", Toksun, has an average windy day of 72 days; Alashankou (Junggar Gate) in the west of Junggar Basin reaches 165 days. The maximum wind speed is near Toksun, and the gale of more than 50 m/s has been detected.

Two inland basins (Junggar Basin and Tarim Basin) and two plateaus (Inner Mongolia Plateau and Ordos Plateau) are the main landforms in this area, and Hexi Corridor is the transitional type between them. Generally, the altitude is 1000 ~ 1500m, and some depressions can be below 500m, while Aiding Lake in Turpan Basin is only-155m, which is the lowest point in China. Plateau and basin are surrounded by high mountains, with an altitude of 3000 ~ 4000 meters above sea level, forming a special mountain environment.

There are few perennial rivers in this area. The main rivers originated in the surrounding mountainous areas, and the water volume gradually decreased after coming out of the mountains, and finally disappeared into inland lakes or moraines, except for the Yellow River and the Irtysh River, which flowed into the Pacific Ocean and the Arctic Ocean respectively. The distribution of groundwater resources is very uneven. Generally, the foothills of mountains and rivers are rich in water resources, with good water quality, and the rest of the ground is extremely poor. The biggest problem of water resources is improper utilization and serious waste. It is estimated that the utilization rate of existing water resources in the vast area west of Helan Mountain is only about 30%. For example, the Tarim River, the largest inland river in China, has an annual runoff of 5 billion cubic meters in Alar, and there are 3.25 billion cubic meters near the dam, but only 65.438+00,000 mu of irrigated farmland.

Poor soil, undeveloped profile, low organic matter content, high salt content and rough and barren texture are generally not conducive to farming. However, there are still a lot of land suitable for farming in the middle and lower reaches of the Yangtze River.

In addition, the distribution of plant resources in this area is very uneven, which can be divided into three zones: ① the east of Wendur Temple-Bailing Temple-Otog Banner-Yanchi is an arid grassland zone, which is dominated by grasses and weeds, covering more than 50%, making it the most abundant grassland in China; ② The desert grassland between this line and Helan Mountain is dominated by weeds, semi-shrubs and small semi-shrubs, with a coverage of 30-50%, which is still a good grassland; ③ The vast area west of Helan Mountain is desert, dominated by shrubs and semi-shrubs, and the coverage rate is mostly below 65,438+00%, and there are still many barren areas. In addition, there is obvious vertical distribution in the surrounding mountainous areas. For example, Tianshan Mountain, Altai Mountain and foothills are desert grasslands, and the slopes are mainly mountain grasslands and coniferous forests.

The development, utilization and protection of climate resources in arid areas of northwest China should be as follows: ① Make full and reasonable use of limited water resources and improve the utilization rate of water. According to the characteristics of severe spring drought, concentrated summer rain and high temperature, crops with drought tolerance, water demand and precipitation distribution are basically the same, and effective moisture conservation measures are taken in dry land cultivation to collect rainwater and snow to prevent drought. Construction of reservoirs, flood control and water blocking, renovation of water conservancy projects, and prevention of canal leakage. For example, the effective utilization coefficient of most channels in Xinjiang is only 0.3 ~ 0.35; If it is raised to 0.5, the spring drought and water shortage of existing cultivated land will be better regulated. Leveling cultivated land and changing the irrigation method of flood irrigation; (2) Returning farmland to grazing in a planned way, planting grass for afforestation, preventing wind and fixing sand. At the front of sandstorm, protect sand-fixing plants and build sand-prevention forest belts to prevent sand dunes from moving forward. Construction of farmland shelterbelt network in Wozhou to prevent soil erosion and green sand dunes; ③ Rational utilization of seasonal grassland and strengthening grassland construction. Due to the high terrain and abundant rainfall, the forage yield in summer and autumn pasture is high and the livestock carrying capacity is large, which is not fully utilized; However, in winter and spring, the grass grows poorly, the livestock carrying capacity is low, and it is overloaded and overgrazing. Therefore, it is an important measure to strengthen grassland construction, adjust some autumn grasslands to winter and spring grasslands, and improve the livestock carrying capacity of winter and spring grasslands.