How many colors are there in the warning signal?

[What's the difference between different color grade warning signals? Now fog can be divided into several color grades, from yellow, orange to red. When these warning signals appear, their meanings are different. In terms of visibility, the yellow warning signal is 12 hours, or the fog will not dissipate in the future 12 hours. Orange means coming in six hours, and the child will not dissipate for the next six hours. Red is very close, that is, two hours. Judging from the standard of visibility, when the yellow warning appears, it means that the visibility due to fog will be around 200-500 meters in the future. Within the visibility range of 200-50 meters, the warning signal is orange. When the visibility is less than 50 meters, the warning signal is red. After the warning signals of different colors occur, people should adjust and arrange their lives according to the warning signal level of heavy fog, and people in different industries should also arrange production activities according to such warning signals. When the yellow warning signal appears, drive as carefully as possible. People try to pay less. When orange and red warning signal come, try not to go outdoors. People with respiratory or asthma diseases should try to stay at home and reduce outdoor activities. [What are the impacts of fog and haze weather on people's production and life? [Zhao] This year's heavy fog has affected traffic and stranded many planes at the airport. When fog and haze are serious, it has a very important impact on traffic, because these industries require very high visibility, and their safety is affected by visibility. Therefore, when the fog and haze are serious, we will prompt them earlier and more timely, and these departments can take measures according to the forecast of the meteorological department. Besides traffic, fog has a great influence on people's health, but it is often ignored by people. For example, when the fog is heavy, the water vapor content is high. If people exercise outdoors, the sweat of the human body is not easy to be discharged, which leads to people feeling chest tightness and rising air pressure. At the same time, there are many pollutants in the fog, such as automobile exhaust, which will affect the throat and eyes after people breathe in the respiratory tract. When there is such weather, we still seldom go out. At the same time, fog has a serious impact on agricultural production. For example, when the fog is heavy, the water vapor is very high, which leads to the weak photosynthesis of plants and affects the growth rate of crops. At the same time, there are pollutants in the fog, which accumulate on the leaves of plants and cause color spots. At the same time, fog has caused great damage to the power sector. Because of the high humidity, the water droplets contain some sulfides and hydrides, which causes the phenomenon of "stroboscopic" of high-voltage line porcelain bottles. At the same time, hydrides and sulfides in water droplets will corrode metals, which can corrode tens of millions of tons of fog every year. [Is fog and haze the same thing? What's the difference between them? [Yang Guiming] Fog and haze are two different weather phenomena from the perspective of meteorology. The main feature of fog is the near-surface layer, which is less than 400 meters high and consists of tiny water droplets in the gas layer below it. Its visibility is very low when it is low, even as low as 50 meters. The main component of smog is a kind of dust, usually called dust, such as sulfuric acid and nitric acid. Meteorology is not called smog, fog is fog, and haze is haze. Fog is mainly water vapor, its relative humidity, fog is generally above 90%, haze is below 80%, that is, the relative humidity is quite different. Another, in terms of visibility, the visibility of fog, defined in the meteorological sense, is below 1000 meters, which is collectively called fog. When the energy is above 1000 meters, we call it light fog, which generally does not affect traffic. However, the visibility of smog is better, about above 1000m, and the smog concentration is higher at1000 m-3000 m. Judging from the color, if it is pure fog, it should be white or gray. Haze is a little yellow. People in South China call it "Caiyun", which has a nice name, but it is quite different from fog. In fact, it is unscientific to combine fog and haze in our life. [What progress has been made in the research of artificial intervention in fog and haze? [Zhao] There are some examples here, and artificial intervention in heavy fog is still effective. According to the nature of fog, it can be divided into cold fog, warm fog and ice fog. The boundary between cold fog and warm fog is another degree. Below 30 degrees, we call it ice fog. According to the characteristics of temperature, artificial fog elimination takes different ways. At present, the most effective way is to disperse the cold fog. For example, cold fog can be reduced by dilution, stirring and heating. In addition to some scientific experiments, there are also some examples of artificial fog elimination in China. For example, from 1966 to 1967, more than 30 experiments were carried out in meteorological, aviation and scientific research departments, and about 20 of them were successful, that is, local fog could be eliminated. 1984 national day, there was an air show at that time, and Nanyuan airport and Xijiao airport were also defogged artificially, which did not affect the national day celebration. The last time was at 1984 Chengdu Shuangliu airport, where the gas was mixed with a high-temperature gas engine to achieve the purpose of fog elimination. But the economic cost of artificial fog elimination is very high, unless it is used for some major national activities or celebrations. In addition, fog removal is a short time, and its economic cost is still relatively high. [Yang Guiming] It is possible to artificially influence the weather to eliminate fog. Fog also includes radiation fog and advection fog. Relatively speaking, radiation fog is not too dynamic and belongs to static state. If it's advection fog, it's fog moving in this direction. It disappears in front of you and comes back. Therefore, artificial defogging can be carried out under very limited conditions. [What services do we have in foggy weather? [Zhao] First of all, there must be a more accurate prediction. The Central Meteorological Observatory has different weather forecast emphases in different seasons. During this period, Yang Zong mainly made weather forecasts such as fog, rainfall and snowfall. After receiving the forecast from the Central Meteorological Observatory, we just mentioned that under the adjustment of several early warning signal defense guidelines, we should arrange our own lives, patients with respiratory infections should go out less or stay indoors, and avoid outdoor activities. For various industries, such as transportation, aviation, water transport, road transport, etc., we must work closely with these departments. Once the fog occurs, we will provide them with accurate forecasts to avoid casualties and property losses. In the past, popular science work in this area was not done enough. In recent years, especially with the development of industrial emissions and urbanization, there are more and more haze weather, so we should strengthen the work of popular science in this area. For example, print some brochures regularly and give some lectures in the community. When such weather comes, some such lectures will be held in the community to tell people how to prevent or avoid adverse weather. Secondly, we should do a good job in the rapid arrival of information. For example, it is also important for the meteorological department to report the forecast and whether it can reach the people quickly after this weather. You know how to defend, but you can't defend well without this information. China Meteorological Bureau will strive to do a good job in meteorological services in the next step. The whole big task is how to make meteorological information reach the people quickly, including places that mobile phone text messages can't reach in the future. We must also find ways to let people know about meteorological information. Ordinary people know how to prevent it, and they can get the forecast information in time, which is very helpful to avoid disadvantages.