184 group weather

There are more than 20 kinds of meteorological disasters, mainly including the following types:

(1) rainstorm: mountain torrents, river flooding and urban water accumulation;

(2) Rain and waterlogging: waterlogging;

(3) Drought: drought in agriculture, forestry and grassland, and water shortage in industry, cities and rural areas;

(4) Dry-hot wind: dry-hot wind and foehn wind;

(5) High temperature heat wave: extreme heat and high temperature, human diseases, burns, and crop ripening;

(6) Tropical cyclones: gale, rainstorm and flood;

(7) Cold damage: crops, livestock and fruit trees are harmed by strong cooling and low temperature;

(8) Freezing injury: frost, crop and livestock freezing injury, water pipes and oil pipes freezing injury;

(9) Freezing rain: wires, branches and roads are frozen;

(10) Freezing: rivers, lakes and seas freeze, and roads freeze after rain and snow;

(1 1) Snow damage: snowstorm, snow;

(12) Hail disaster: destroying crops and houses;

(13) Wind disaster: falling trees, reversing houses, reversing cars and reversing boats;

(14) Tornado: local destructive disaster;

(15) Lightning: lightning casualties;

(16) Continuous rain (lewd rain): it is not conducive to crop growth and development, grain mildew, etc.

(17) dense fog: human diseases and traffic jams;

(18) low-altitude windshear: aviation accident;

(19) acid rain: crops are harmed.

Summary of disastrous weather in China

China is located in the southeast of Eurasia, bordering the Pacific Ocean, and most areas have monsoon climate. Winter is mainly controlled by polar continental air mass or denatured polar air mass, and northwest wind, north wind and northeast wind prevail; Summer is controlled by tropical and subtropical marine air masses and continental air masses, and southwest wind, south wind and southeast wind prevail. In this context, the variability of meteorological elements such as precipitation, temperature, wind and clouds in China is large and often sudden, which leads to various meteorological disasters.

There are many kinds of meteorological disasters affecting our country, with high intensity, high frequency and serious losses. With the development of economy and the growth of social wealth, the losses caused by meteorological disasters are increasing. Accurate weather forecast is one of the most important scientific bases for government departments at all levels to guide disaster prevention and relief. According to statistics for many years, among all kinds of meteorological disasters, flood disaster is the most serious one, and drought is the most extensive one. In addition, there are tropical cyclone disasters, cold waves and strong cold air disasters, sandstorms, wind disasters, hail disasters, frost disasters and snow disasters. These disasters affect a wide range and are often related to the anomalies of large-scale weather systems, which is also the main reason for the occurrence of smaller weather disasters.

The change of large-scale weather system in China is closely related to the East Asian monsoon. The flood season from May to September every year is a frequent period of disastrous weather in China, and the large-scale precipitation distribution and drought and flood disasters in this period are largely controlled by the summer monsoon. After the summer monsoon broke out, the main rain belt in China began in South China and gradually moved northward with the summer monsoon. Because the intensity of the monsoon, the speed of advancing northward and the time that the monsoon rain belt stays in a place are different every year, the activities of the main rain belt are different every year. The formation of regional rainstorm in China history is closely related to the change of East Asian summer monsoon. The southerly airflow in the lower layer of summer monsoon not only transports energy and water vapor to the rainstorm area, stimulates and maintains the rainstorm, but also cuts off the cold air in the middle and high latitudes, resulting in continuous drought outside the rain belt in China. At the same time, it is also the background condition for the formation of mesoscale severe convective weather disasters.

East Asian monsoon airflow is the result of the interaction of large-scale weather systems as members of the whole East Asian monsoon circulation system. Among them, the western Pacific subtropical high plays a particularly important role in China's weather and climate. The subtropical high is located in the middle of the troposphere in the northern hemisphere, over the western Pacific Ocean, with Meiyu front in the north and East Asian tropical monsoon circulation in the south in summer. It is not only directly related to the establishment of the South China Sea summer monsoon, but also its northward jump and advance and retreat are closely related to the changes of Chinese mainland subtropical summer monsoon and its rain belt, which is the direct reason for the formation of large-scale weather stages in China. Generally speaking, the location of subtropical high determines the location of the main rain belt in China, and its strength and stability determine the overall situation of drought and flood in flood season in China. Therefore, it is a crucial scientific issue to study the motion law and mechanism of the western Pacific subtropical high.

An important system closely related to the western Pacific subtropical high is the South Asian high. It is a powerful and stable atmospheric activity center located in the upper troposphere and lower stratosphere in South Asia in summer, and also an important member of the global subtropical high. Although the influence of the upper circulation system on precipitation distribution is not as direct as that of the lower circulation system, compared with the lower circulation system, the upper circulation system is unusually more stable, more durable and has some advance, so its relationship with the atmospheric circulation in the northern hemisphere in summer and the weather and climate in China can not be ignored.

Tropical cyclone is the main tropical weather system that directly affects the weather in China. Tropical cyclones land in China every year, causing different degrees of disasters. The path and intensity of tropical cyclones are not only related to their own structural characteristics, but also depend on the activities of subtropical high and cold air to a great extent. At the same time, the activity of tropical cyclones also has a negative impact on the activity of subtropical high.

Another aspect that determines the weather characteristics in East Asia is the weather system at middle and high latitudes. During the winter monsoon, the tropical and subtropical systems basically withdrew from Chinese mainland, and the westerly ridge at high altitude and the corresponding high and low pressure systems at low altitude completely controlled China. Even during the summer monsoon, they still control the northern part of China and have an important influence on the weather in the south. For example, most heavy rains in China are directly or indirectly related to cold air activities. Compared with the fluctuation of the moving westerly belt, the blocking high in East Asia is more significant to the weather in East Asia. The blocking situation is a typical manifestation of the persistent anomaly of atmospheric circulation. Its formation, maintenance and collapse not only affect the weather anomaly in this area, but also cause the change of atmospheric circulation in the northern hemisphere. The research and forecast practice show that the blocking situation in Asia, especially in East Asia, is the main circulation background of persistent drought and flood in summer in China. Extraordinary or extraordinary flood years in the Yangtze River Basin of China (1954, 1969, 1980, 1983,1993,65433). The establishment and disintegration of the blocking situation in East Asia and the Pacific Ocean in winter and spring are closely related to the outbreak of cold waves in China, especially strong cold waves, and also to the dusty weather in northern China. Therefore, the blocking situation is extremely important in the large-scale system that affects the weather change in China.

Meteorological disasters account for more than 70% of all kinds of natural disasters in China every year. Every year, more than 500 million mu of farmland is affected by various meteorological disasters, and the population affected by major meteorological disasters such as drought, rainstorm, flood and typhoon is nearly 600 million. Since the 1990s, the direct economic losses caused by meteorological disasters in China have reached an average of 200 billion yuan each year, accounting for 3%-6% of GDP in that year. With the continuous growth of economy and population, its absolute value will further increase.

According to the loss degree caused by meteorological disasters, the meteorological disasters in China are ranked as follows: flood, typhoon, drought, chilling injury, hail, thunderstorm, gale, dry and hot wind in northern winter wheat area, lightning strike and fire. In addition, snowstorms in pastoral areas, ice floods in the Yellow River, fog disasters in cities and highways, and sandstorms in northern areas have also caused a large number of human and animal casualties and economic losses.

Flood disaster refers to the phenomenon that the water level rises abnormally due to meteorological reasons, breaks through dikes, floods fields and houses, drowns people and animals, and causes diseases. Throughout history, floods have always been a great threat to human beings and other creatures. According to statistics, the average annual flood loss in China in 1990s was as high as 6543.8+0.2 billion yuan, accounting for 2.4% of the gross national product. 199 1 floods in the Yangtze River and Huaihe River, 1994 floods in the Pearl River and 1998 floods in the Yangtze River, Songhua River and Nenjiang River all caused great economic losses to the country. During the period of 1998, 29 provinces (autonomous regions and municipalities directly under the central government) suffered from floods in different degrees. According to the statistics of various provinces, 4 150 people died and the direct economic loss was 2551000000 yuan (People's Republic of China (PRC) and Ministry of Water Resources, 1999). Flood disaster has become an important restricting factor for China's economic development.

Typhoon (including tropical storm, strong tropical storm and typhoon) refers to a tropical cyclone with an average wind force of 8 or above near the center. Strong winds brought by typhoon disasters will overturn ships, destroy houses and other facilities, huge waves can break through seawalls, and heavy rains can cause flash floods. Typhoon disasters are fierce and have the characteristics of acute suddenness. China is a country with severe typhoon disasters in the world, with an average of 7 typhoons landing every year. The average annual economic loss caused by typhoons in Chinese mainland is 24.6 billion yuan, and the death toll is as high as 570.

Drought disaster refers to the disaster phenomena such as crop death and insufficient drinking water for people and livestock caused by long sunshine, no rain or little rain, soil water shortage and dry air. Considering the weather conditions, drought also includes dry hot wind, high temperature and heat wave. In the past 40 years, the average drought-affected area of farmland in China has reached more than 300 million mu every year, causing disasters 1. 1.00 billion mu, and the grain output has been reduced by tens of billions of kilograms. In the 1990s, droughts occurred frequently in the north of China, and six severe droughts occurred in the Central Plains. From February to May in 20001year, the drought disaster with the longest duration, the widest range and the heaviest degree occurred in most parts of northern China in recent1year. The drought-affected area of farmland in China reached 34 1 10,000 mu,158,000 people,1.1.4,000 large livestock had temporary drinking water difficulties.

Cold wave is an abnormal cold air coming like a flood, commonly known as "cold wave". When the strong cold air in polar regions or high latitudes rapidly advances to the middle and low latitudes, it causes a wide range of severe cooling, often accompanied by strong winds, dust, snowfall (rain), freezing damage and other comprehensive disastrous weather phenomena, which are called cold waves and have a serious impact on the large-scale disastrous weather in China. The average cold wave affecting China is 5 ~ 6 times a year, and it can appear in autumn, winter and spring from September of that year to May of the following year.

Hail is solid precipitation condensed by water vapor in the air, which is spherical or conical with transparent layer and opaque layer. Hail mainly occurs in the mountains and foothills from May to September, with a range of only a few kilometers to dozens of kilometers, which has obvious locality and dispersion. This is a serious meteorological disaster. Short and violent hail will cause crop failure, fruit leaf withering, grassland destruction, human and animal casualties, thus seriously affecting the agricultural economy and farmers' income.

Sandstorm refers to the weather phenomenon that strong winds blow up a lot of dust on the ground, making the horizontal visibility less than 1 km. The frequent sandstorms in northern China every spring not only cause huge natural disasters, but also seriously endanger Beijing, Tianjin and other places, and spread to the whole country. Strong sandstorms can cause house collapse, traffic power interruption, fire, human and animal casualties, pollute the natural environment, destroy crop growth, and cause serious losses and great harm to national economic construction and people's lives and property safety. The sandstorm weather process that occurred from March 18 to March12, 2002 is the largest, strongest, most serious and longest-lasting one since 1990s, and it has attacked the land of northern China1400,000 square kilometers, with the affected population1300,000 yuan.

Bad meteorological conditions may also lead to various other secondary or derivative disasters, such as large-scale heavy rainfall and floods, which may lead to mudslides and landslides in specific mountainous areas. In some areas (especially mountainous towns), high-density meteorological and geological disasters (mudslides and landslides) that broke out in a short time and accumulated for a long time seriously threatened people's lives and property. In recent years, the frequency of debris flow and landslide disasters and the number of deaths have increased significantly; Continuous precipitation or continuous high temperature and drought will also promote the outbreak of large-scale pests and diseases. Therefore, meteorological disaster is an important primary disaster system.

In short, with the development of social economy in China, the losses caused by meteorological disasters, especially disastrous weather, will become more and more serious, and the requirements for meteorological services for disaster prevention and mitigation will become higher and higher. Because of its small scope, great intensity and fierce strength, disastrous weather often appears in marginal areas. Although all aspects are extremely concerned about this, it is difficult for the existing conventional meteorological observation network relying on traditional technical means to capture its traces in time, and it is even more difficult to make accurate local weather forecasts in advance. To do a good job in disaster weather early warning and forecasting service, we must first develop remote sensing and telemetry technology with continuous observation and high space-time density, and strengthen the construction of comprehensive observation system. The construction, development and application of China's new generation weather radar network, which is mainly based on Doppler weather radar, will provide extremely effective tools and information for monitoring, early warning and short-term forecasting services of severe weather in China, especially small and medium-sized severe weather.

Disastrous weather forecast measures

(1) Types and standards of disastrous weather

1. Tropical cyclone: according to the maximum wind force near its center, it can be divided into four types according to the current domestic regulations:

(1) tropical depression: the maximum wind force near the center is less than 8 (wind speed is less than17.2m/s);

(2) Tropical storm: the maximum wind force near the center reaches 8-9 (wind speed17.2-24.4m/s);

(3) Severe tropical storm: the maximum wind force near the center reaches 10- 1 1 (wind speed is 24.5-32.6m/s);

(4) Typhoon: The maximum wind force near the center 12 or above (the wind speed is above 32.7m/s). (See attached table for details)

attached table

Maximum wind force near the center

The name of international tropical cyclone is 1989 65438+ 10/.

6~7

tropical depression

8~9

tropical storm

10~ 1 1

Severe tropical storm

12 or more.

typhoon

2. Strong wind: refers to the strong wind that is caused by non-tropical cyclones and the average wind force is above Grade 6 (wind speed10.8-13.8m/s).

Strong winds at sea transmit information through typhoon signals. China's typhoon signal suspension standards are as follows (see page 184).

3. Rainstorm: refers to the precipitation with a total precipitation of more than 50 mm within 24 hours. The unified national standard is to divide the rainfall into three levels: rainstorm (50.0-99.9 mm), heavy rainstorm (100.0-249.0 mm) and extremely heavy rainstorm (250.0 mm or more).

(two) the name and standard of severe weather warning.

According to the type, intensity, influence in the morning and evening and the degree of forecast guarantee, the disastrous weather in the region can be roughly divided into public release and internal release. Version names are divided into:

1. Message: When the disastrous weather is far away from or has not affected the area or is expected to be generally harmful, you can issue a "message" to report the disastrous weather as needed, or report or issue an early warning in the form of a "message".

2. Early warning: When it is predicted that disastrous weather will attack or affect the local area or sea surface in the next 1-2 days, and the impact is great, an "alarm" will be issued.

3. Emergency warning: When it is predicted that disastrous weather will attack the local area or the sea surface in the next 24 hours, and the harm is very great, an "emergency warning" will be issued.

How did the disastrous weather change in space happen?

Disastrous weather events in space, in layman's terms, refer to the violent disturbance of the space environment between the sun and the earth caused by solar eruption and its disastrous influence on human activities.

Solar-terrestrial space environment, sometimes called near-earth space environment, generally refers to the vast space from near the earth's surface to the sun. Because the earth's atmosphere is about 60 kilometers, atmospheric molecules are gradually ionized due to the radiation of solar extreme ultraviolet rays and X-rays, and the degree of ionization increases with the increase of height, but there are still frequent collisions between ions and neutral molecules. This area seriously affects the propagation of radio waves. People call this part of the atmosphere the ionosphere. Above a height of several Qian Qian meters, because the atmosphere is very thin, air molecules are completely ionized, and the movement of ionized components is controlled by the earth's magnetic field, so the earth's atmosphere above the ionosphere is called the earth's magnetosphere. Due to the huge mass of the sun, the matter inside the sun is affected by great pressure and high temperature under the action of gravity, forming a fusion reaction of nuclear nuclei, thus releasing huge energy, and the outer atmosphere of the sun remains ionized at high temperature. Constantly released into interplanetary space, its speed is usually hundreds of kilometers per second in the calm state of the sun, which is called the solar wind. Under the action of the solar wind, the earth's magnetic field and its magnetosphere under its control are deformed as a whole, compressed towards the sun and elongated on the back. The magnetosphere is separated from the solar wind at the top, and the earth's magnetosphere is shaped like a long-tailed comet. With the development of science and technology and the deepening of human understanding of nature, this space field has become a new environment for human activities. The orbital heights of various application satellites range from several hundred kilometers to 20,000 to 30,000 kilometers, while specially designed exploration satellites can reach other planets. In addition, many ground technology systems use or are influenced by the space environment.

Now look at the sun, which is the most important source of energy for the earth. The frequency band of solar radiation is very wide, ranging from short-wavelength X-rays, extreme ultraviolet rays, ultraviolet rays, visible light and infrared rays to radio waves, and most of the energy is concentrated in the visible and infrared bands. The radiation of the sun in the visible band is equivalent to the blackbody radiation of 6000 degrees. However, those processes that cause X-rays and extreme ultraviolet rays may have high temperatures of several million degrees. There is still a small amount of energy from the sun in the form of matter and magnetic field. For example, the solar wind mentioned above sometimes ejects a large amount of ionized matter from the upper part of the solar atmosphere (corona) with the solar magnetic field, which is called coronal mass ejection.

The condition of the sun is not stable, but in a state of constant activity. As far as the output of far ultraviolet rays, X-rays, high-energy electrons, protons and solar substances that cause changes in the space environment is concerned, the solar activities that cause them to change can be divided into two types: gradual type and explosive type. Sunspot is a typical gradual solar activity, which is a low temperature and strong magnetic field area in the lower layer of the solar atmosphere. Its activity level is related to solar electromagnetic radiation, especially ultraviolet radiation. The radiation intensity of X-rays and other bands is obviously related to many explosive activities. Coronal hole is another gradual solar activity, which is a unipolar magnetic field region with relatively thin material density in the outer atmosphere of the sun. The magnetic field lines lead from here to interplanetary space, which is the birthplace of high-speed solar wind. Explosive solar activities mainly include solar flares and coronal mass ejections. The energy conversion in the violent physical process in the corona can accelerate some coronal materials to leave the sun and throw them into interplanetary space, with speeds ranging from several hundred to more than 1,000 kilometers per second. The solar magnetic field in the separation area interacts with the earth's magnetic field when it flows through the earth, resulting in geomagnetic disturbance and other effects. Solar flare is a common local solar burst phenomenon, accompanied by the great enhancement of short-band electromagnetic radiation and protons such as ultraviolet rays and X-rays. In addition, the above-mentioned magnetospheric disturbance can also provide energy for charged particles in the earth's magnetic tail, accelerate their settlement along the magnetic field lines to the polar ionosphere, and produce an effect similar to proton events. It is this complex interaction between the sun and the earth that interferes with the near-earth space environment and forms a series of space weather disasters.

The period of solar activity is about 1 1 year. In the year of maximum solar activity, solar bursts occur frequently, and the intensity is usually much stronger, but the general visible light radiation does not change obviously in the high and low years of solar activity.

It takes one to three days for matter from the sun to reach the earth, and only a few hours for high-energy protons. However, X-rays and extreme ultraviolet rays travel at the speed of light and reach the earth in a little over eight minutes. They interact with the earth's upper atmosphere and the earth's magnetic field, which strongly affects the near-earth space environment. Although disturbances are generally not directly perceived by people, they can cause catastrophic events in space. They can be roughly divided into the following categories:

The first is the impact on the orbit and life of artificial satellites: the disturbance of upper atmosphere density causes the irregular perturbation of satellite orbit. In the case of serious disturbance, the atmospheric density can be increased by more than 10%, which greatly increases the air resistance of the satellite, thus significantly shortening the service life of the satellite. Secondly, the influence on the satellite electronic system: when the object running in ionized gas is in balance with the environmental potential, it has a negative potential. In the case of strong disturbance, the average temperature of ionized gas is greatly increased, and the satellite surface can be charged up to tens of thousands of times. High-energy charged particles from the sun or other sources can penetrate satellites and be deposited in the large-capacity memory chips of some computers. This kind of deposited charge leads to the polarity reversal of memory cells, which leads to the error of computer storage data or the disorder or even crash of programs, that is, the so-called single event inversion event. In addition, it also affects the propagation of radio waves: on the global ground, short-wave communication is realized through ionospheric reflection. Radio information and data transmission between the satellite and the ground must pass through the ionosphere, and all radar, navigation and positioning systems on the ground and in the air inevitably rely on electromagnetic waves. Therefore, the influence on radio wave propagation involves all modern information systems. The sudden increase of electron density at the ionosphere bottom caused by flare and the enhancement of ionization in polar region during proton events strongly absorbed radio wave energy, interrupted short-wave communication and increased noise interference in the sky. When the ionosphere is disturbed, the increase of the total electron content increases the propagation delay of radio waves, and the irregular structure makes the amplitude and phase of high-frequency signals unstable (flicker), which greatly affects the accuracy of navigation and positioning.