Differences between important weather processes and disastrous weather processes.

Important weather processes: precipitation, tornado, snow cover, snow cover, hail, thunderstorm, sight distance obstacle (haze, floating dust, sandstorm, fog) and other important weather.

Precipitation: refers to the phenomenon that water vapor in the air condenses and falls to the surface, including two parts. One is that the water vapor in the atmosphere condenses directly on the ground or the surface of ground objects and at low altitude, such as frost, dew, fog and fog, which is also called horizontal precipitation; The other part is water vapor condensate falling from the air to the ground, such as rain, snow, hail, rain, etc., also called vertical precipitation. However, pure frost, pure dew, pure fog and pure fog are not treated as precipitation. In China, according to the ground observation standard of National Meteorological Administration, precipitation only refers to vertical precipitation, and horizontal precipitation is not treated as precipitation. Precipitation does not necessarily happen, only effective precipitation will happen. In one day, the precipitation above 50 mm is rainstorm (torrential rain), above 25 mm is rainstorm, below 10-25mm is moderate rain, below10mm is light rain, above 75mm is rainstorm (torrential rain), and above 200mm is torrential rain.

Tornado: short for tornado, water vapor rises to the sky and turns into clouds when it is cold. When the temperature of the cloud cluster is low, it cools the surrounding water vapor, and the volume of water vapor shrinks, and the surrounding air vapor supplements the space. The water vapor rising below the cloud group rises linearly, and the water vapor molecules shrink smaller and smaller in the rising process, showing a funnel shape. The cooling volume of rising water vapor molecules is shrinking, and the gas molecules under the cloud are constantly replenishing the space, resulting in strong winds. Because the cooling volume of water vapor is shrinking, the gas in some surrounding spaces comes unevenly, forming a tornado.

Snow: also known as snow cover or snow cover, refers to the snow layer covering the land and sea ice.

Rime: A glassy, transparent or dim ice sheet with rough surface formed when supercooled precipitation hits the surface of an object with a temperature equal to or lower than zero degrees Celsius. Commonly known as "tree hanging", it is also called ice and tree condensation, and the rain that forms a rain is called freezing rain.

Hail: It is also called "hail", commonly known as hail, and it is called "Lengzi" in some areas (such as Xuzhou), which is the most common in summer or at the turn of spring and summer. It is some ice particles as small as mung beans and soybeans and as big as chestnuts and eggs. The water on the local surface is vaporized by the sun and then rises into the air. A lot of water vapor condenses into clouds, and after being liquefied by cold air, the dust in the air is used as the condensation core to form raindrops, and the raindrops are getting bigger and bigger. If there are more clouds, it will rain. If exposed to cold air without condensation nuclei, water vapor will condense into ice or snow, which is snow. If the temperature drops sharply, it will form a bigger ice mass, which is hail.

Thunderstorm: It is a local convective weather accompanied by lightning and lightning. Usually accompanied by heavy rain or hail, and even accompanied by snowstorm in winter, it belongs to a strong convective weather system.

Haze: also known as haze and ash haze, it refers to the turbidity phenomenon formed by the suspension of a large number of particles such as smoke and dust of unknown reasons. The core substance of smog is dust particles suspended in the air, which are called aerosol particles in meteorology. In recent years, with the increasingly frequent "smog" weather phenomenon, air quality has gradually deteriorated. Haze contains hundreds of atmospheric chemical particles, which intrude into human respiratory tract and lung lobes unsuspecting, thus causing respiratory diseases, cardiovascular diseases, blood system, reproductive system and other diseases, such as pharyngitis, emphysema, asthma, rhinitis, bronchitis and other inflammation. Long-term exposure to this environment will also induce lung cancer, myocardial ischemia and injury. Smog also often causes traffic accidents.

Floating dust: In meteorology, floating dust is called the weakest floating dust weather. Floating dust is formed by fine particles such as dust and sand floating in the air after sandstorm or sand blowing in remote or local areas, commonly known as "falling yellow sand". When it appears, the distant objects are khaki, the sun is pale or yellowish, and the visibility is less than 10 km and greater than 1 km, and there is basically no obvious wind. In dusty weather, people's eyes, nose, throat, skin and other direct contact parts will be damaged to a certain extent, mainly manifested as runny nose, tears, cough, expectoration and other irritating symptoms and allergic reactions, which can seriously lead to skin inflammation and conjunctivitis. In dusty weather, it is necessary to minimize going out and close doors and windows at home in time, especially for patients with chronic bronchitis and the elderly and children with relatively weak resistance.

Sandstorm: it is a general term for sandstorm and sandstorm. It refers to a severe sandstorm weather phenomenon in which strong winds blow and drag a large amount of sand and dust on the ground into the air, making the air particularly turbid and the horizontal visibility less than one kilometer. Among them, sandstorm refers to a sand-laden storm formed by strong wind blowing a large amount of sand near the stratum; Sandstorm is a storm formed by strong winds, which brings a lot of dust and other particles into the sky.

Fog: When the relative humidity reaches 100%, the water vapor in the air will condense into tiny water droplets suspended in the air, which will reduce the ground visibility. This weather phenomenon is called fog. Fog is more common in spring from February to April. When the visibility in the atmosphere is lower than 1 km due to the condensation of suspended water vapor, meteorology calls this weather phenomenon fog.

Disastrous weather processes: cold wave, tropical storm and typhoon, strong wind and dry hot wind, drought and flood.

1, cold wave

In the winter half year, the cold air in the north broke out southward on a large scale, and severe weather such as strong wind, cooling, rain, snow and freezing occurred in the passing area. Or it can be expressed as: the cold air entrenched in high latitudes suddenly leaves the source area and goes south on a large scale in a specific weather situation, resulting in severe cooling along the way, accompanied by northerly winds, frost, rain and snow, sandstorms and other weather phenomena. This weather process is called cold wave. During the cold wave, the most prominent weather feature is the strong wind cooling. The wind direction changes suddenly, the wind force increases, the ground pressure rises, the temperature and humidity drop sharply, and it is accompanied by rain and snow. It can be seen that cold wave is a strong cold air activity. Cold waves mostly occur in winter half a year. The freezing injury and wind disaster caused by cold wave have adverse effects on production and construction, transportation, people's life and tourism activities.

The standard of cold wave ① cold wave; A cold air invasion caused the lowest temperature in the middle and lower reaches of the Yangtze River and its north to drop by 10℃ or more within 48 hours, and the lowest temperature in the middle and lower reaches of the Yangtze River reached 4℃ or below. There are 5~7 strong winds on the land equivalent to three administrative regions, and there are more than 7 strong winds in the Bohai Sea, the Yellow Sea and the East China Sea, which are called cold waves. ② Strong cold wave; If the minimum temperature drops above 14℃ within 48 hours, there will be strong winds of magnitude 5~7 in 3~4 administrative regions on land, and strong winds of magnitude 7 or above will appear in all coastal waters, which is called a strong cold wave. ③ General cold air activity; Any weather process that does not meet the above standards is called general cold air activity.

China has a vast territory, complex terrain, great climate difference between north and south, and different production activities in different places. It is difficult to meet the service requirements of various places by adopting the same cold wave standard throughout the country. Therefore, many meteorological stations have supplemented and revised the cold wave standards suitable for the local area according to the local specific conditions. Therefore, tourists should not only listen to the weather forecast of the Central Meteorological Observatory, but also pay attention to the weather forecast of local stations in the areas they visit.

There are frequent cold air activities in China all the year round, in which the average cold wave reaches 6.2 times a year (1955 to 1975), which is 10 times for many years, and only/kloc-0 times for teenagers.

When the cold wave strikes, the most prominent weather performance is strong wind cooling, and other weather phenomena such as sandstorm, rain and snow vary according to regions and conditions.

Second, tropical storms and typhoons.

Tropical storm: Tropical cyclones often occur in tropical oceans. When tropical cyclones develop to a certain extent, they are called typhoons in the western Pacific, hurricanes in the Atlantic, Willie-Willie in Australia and storms in the Bay of Bengal. Cyclones that occur in and develop in the tropics are called tropical cyclones, which are low pressures generated on the surface of tropical oceans at low latitudes.

Typhoon: a strong tropical cyclone with warm center structure that occurs on the surface of tropical ocean. Not every tropical cyclone can reach typhoon intensity.

(2) The standards and names of tropical cyclones of the Typhoon Committee of the International Meteorological Organization.

1, low pressure area; The center position cannot be determined, and the average maximum wind speed near the center is less than 34 knots (level 8, wind speed? 17.2m/s).

2. Tropical depression; The center position can be determined, and the average maximum wind speed near the center is less than 34 knots (level 8, wind speed? 17.2m/s).

3. Tropical storms; The average maximum wind speed near the center is 34-47 knots (8-9,17.2-24.4m/s).

4. Strong tropical storm; The average maximum wind speed near the center is 48-63 knots (10-1,24.5-32.6 m/s).

5. Typhoon; The average maximum wind speed near the center is above 64 knots (≧ 12, ≧ 32.7m/s).

(3) Standards and names of tropical cyclones in China.

Since 1989, China has adopted the unified standard stipulated by the World Meteorological Organization (WMO), that is, tropical cyclones are divided into four grades according to the maximum average wind force near the center of tropical cyclones:

1, tropical depression: wind

2. Tropical storm: the wind force is 8-9 (wind speed17.2-24.4m/s).

3. Severe tropical storm: wind force 10- 1 1 (wind speed 24.5-32.6m/s).

4. Typhoon or hurricane: wind force ≧ 12, wind speed ≧ 32.7m/s).

Third, strong winds and dry hot winds.

(1) Gale: The wind with a wind force greater than 6 (12m/s) is called gale.

(2) Dry-hot wind: it is a comprehensive weather phenomenon with high temperature and low humidity and a certain wind force. Some places also call it "dry wind", "fire wind", "hot wind" and "dry wind". It often appears in late spring and early summer, which is harmful to wheat and cotton, and the strong one can endanger the normal growth of trees and make them dry and defoliate.

Fourth, drought and flood.

Drought and flood refer to abnormal weather and climate caused by abnormal precipitation in a short period of time. Obviously, continuous lack of rain leads to drought, while heavy rain leads to waterlogging.