How many colors are there for early warning signals?

[What are the differences between warning signals of different color levels? ] [Zhao Linna] Nowadays, heavy fog is roughly divided into several color levels, from yellow, orange, and red. When these warning signs occur, they have different meanings. In terms of visibility, a yellow warning signal is that heavy fog will occur within 12 hours or will not dissipate within the next 12 hours. Orange means the baby is coming within 6 hours and will not disappear within the next 6 hours. Red means it's very close, just 2 hours. From the perspective of visibility standards, when a yellow warning occurs, it indicates that fog will affect visibility in the future at about 200-500 meters. Within the visibility range of 200-50 meters, the warning signal is orange. For visibility less than 50 meters, the warning signal is red. After the early warning signals of different colors occur, people should adjust and arrange their lives according to the level of the early warning signals of fog, and people in different industries should also arrange production activities according to such early warning signals. When a yellow warning signal occurs, try to drive with caution. People try to go out as little as possible. When the orange and red warning signals come, try not to engage in outdoor activities. People with respiratory or asthma diseases should stay at home as much as possible and reduce outdoor activities. [What impact does fog and haze weather have on people’s production and life? ] [Zhao Linna] This year's heavy fog has affected traffic, leaving many planes stranded at the airport. When fog or haze is severe, it has a very important impact on traffic, because these industries have very high visibility requirements, and their safety is affected by visibility. Therefore, when thick fog and haze are severe, we will issue early and timely reminders, and these departments can take measures based on the forecasts of the meteorological department. In addition to its impact on traffic, fog has a great impact on people's health, but it is often ignored by people. For example, when there is heavy fog, the water vapor content is very high. If people are active and exercising outdoors, the body's sweat is not easily discharged, causing people to have chest tightness and increased air pressure. At the same time, there are many pollutants in the fog, such as car emissions. When people breathe in, it will affect the throat and eyes. When the weather is like this, it is better to go outdoors less often. 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, causing the photosynthesis of plants to not be very strong, affecting the growth rate of crops. At the same time, the fog contains pollutants, which accumulate on the leaves of plants, causing stains. At the same time, fog causes great damage to the power sector. Due to the high humidity, water droplets contain some sulfides, hydrides, etc., causing "stroboscopic" phenomena in high-voltage line porcelain bottles. At the same time, the hydrides and sulfides in the water droplets will cause corrosion to metals, and tens of millions of tons of mist can be corroded every year. [Are fog and haze the same thing? What is the difference between them? ] [Yang Guiming] Fog and haze are two different weather phenomena from a meteorological point of view. The main characteristic of fog is the layer near the ground. Its height is probably no more than 400 meters, which is the tiny air layer below. Made of water droplets. When its visibility is relatively low, it is very low, even as low as 50 meters. The main component of haze is a kind of dust, usually called dust, such as sulfuric acid, nitric acid and other tiny particles. Meteorologically speaking, it is not collectively called haze. Fog is fog, and haze is haze. Fog is mainly composed of water vapor. Its relative humidity is generally above 90 for fog and below 80 for haze. There is a big difference in relative humidity. Another one, in terms of visibility, the visibility of fog is defined in a meteorological sense. It is below 1,000 meters, collectively called fog. When the intensity is above 1,000 meters, we call it light fog, which generally does not affect traffic. But the visibility of haze is better, probably above 1,000 meters, and between 1,000 meters and 3,000 meters, the concentration of haze is higher. In terms of color identification, if it is pure fog, it should be white or gray. The haze is a bit yellowish in color. People in South China call it "colorful clouds". Its name is very beautiful, but it is actually very different from fog. In our daily life, we talk about fog and haze together, which is actually not very scientific.

[What progress has been made in the research on artificial intervention of fog and haze? ] [Zhao Linna] There are some examples where artificial intervention in fog is still effective. According to the nature of fog, it is 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 methods. The most effective way at present is to dissipate cold fog. For example, for cold fog, dilution, stirring, heating, etc. can be used to reduce it. In this regard, in our country, in addition to some scientific experiments, there are also some examples of artificial fog elimination. For example, from 1966 to 1967, more than 30 experiments were conducted in the meteorological, aviation and scientific research departments, and about 20 of them were Success means that local fog can be eliminated. During the National Day in 1984, there was an aviation show, and artificial fog elimination work was also carried out at Nanyuan Airport and Xijiao Airport, so that the National Day celebration was not affected. The most recent one was in Chengdu Shuangliu Airport in 1984, where a high-temperature gas engine was used to mix the gas to achieve the purpose of eliminating fog. However, the economic cost of artificial fog elimination is very high, unless it is used for some major state events or celebrations. In addition, fog elimination only lasts for a short period of time, and its economic cost is still relatively high. [Yang Guiming] Artificial weather modification and fog elimination are possible. Fog also includes radiation fog and advection fog. Relatively speaking, radiation fog is not too dynamic and is in a static state. If it is advection fog, it is a stream of fog moving in this direction. It disappears in front of you and comes again behind you. Therefore, artificial fog elimination can be achieved under very limited conditions. [What services do we provide for haze weather? ] [Zhao Linna] First of all, we need to have a more accurate forecast. The Central Meteorological Observatory has different weather forecast priorities in different seasons. During this period, Chief Yang is focusing on weather forecasts such as fog, rainfall, and snowfall. After receiving the forecast from the Central Meteorological Observatory, we arranged our lives in accordance with the several early warning signal defense guidelines mentioned earlier. For patients with respiratory infections, we should go out less or not at all, and avoid outdoor activities. For various industries, such as transportation, aviation, water transportation and road transportation, we must work closely with these departments. Once heavy fog occurs, we will accurately provide them with corresponding forecasts to avoid casualties of people and property. In the past, science popularization work in this area was not enough. In recent years, especially as industrial emissions and urbanization have developed more and more, and there are more and more smog and haze weather, science popularization work in this area should be strengthened. For example, some brochures are printed regularly and some lectures are held in the community. When such weather comes, some such lectures are held in the community to tell the people how to prevent or avoid the weather that is not good for them. Secondly, we must ensure the rapid arrival of information. For example, when the meteorological department issues a forecast, it is also critical whether it can reach the hands of the people quickly when there is such weather. You know how to defend, but you can't do a good defense without getting this information. The China Meteorological Administration will make great efforts to provide meteorological services in the next step. The whole big task is how to make meteorological information reach the people quickly, including places where mobile phone text messages cannot reach in the future. We must also find ways to make meteorological information reach the people. in hand. The common people know how to prevent and can get timely forecast information, which is very helpful in seeking advantages and avoiding disadvantages.