How did advection fog form the fog warning signal?

Lead: As we all know, fog is a weather phenomenon with a large number of tiny water droplets floating in the air, usually milky white. Advection fog is a kind of fog. So, do you know how advection fog came into being? How is the fog warning signal divided? Let's have a look.

How did advection fog come into being?

1, the temperature difference between warm air and the ground is large.

When the temperature difference between the warm air and the ground is large, the water vapor at the bottom of the warm air will condense into fog when it meets the low temperature of the ground, which may form the scene of advection fog.

2. Appropriate wind direction and speed.

The formation of advection fog needs the influence of suitable wind direction and speed.

Specifically, to form the advection fog, a horizontal wind of 2-7m/s is needed.

Such a wind can achieve two purposes:

1, providing stable warm air continuously, which provided conditions for the formation of advection fog.

According to the above analysis, it can be explained why advection fog mostly occurs in high latitudes.

In high latitudes, the temperature difference between spring and autumn will be relatively large, so that the ground temperature will be low and the temperature will be relatively high, forming the environmental state of advection fog.

The influence of foggy weather

In foggy days, the combination of pollutants and water vapor in the air will make it difficult for pollutants to spread and settle, which makes most pollutants gather at the height where people often move. And some harmful substances will become more toxic when combined with water vapor, so the air pollution in foggy days is much more serious than usual. Another reason that needs to be emphasized is that the particles that make up the fog core are easy to be inhaled and stay in the human body, while the amount of air inhaled during exercise is much more than usual, and there will be a lot of particles inhaled during exercise in foggy days, further aggravating the harm of harmful substances to the human body.

In this environment for a long time, the human body will inhale harmful substances, consume nutrients, cause internal injuries to the body, and easily induce or aggravate diseases. In particular, some people with environmentally sensitive diseases, such as bronchial asthma, pneumonia and other respiratory diseases, will have normal blood circulation obstruction, leading to cardiovascular diseases, hypertension, coronary heart disease, cerebral hemorrhage and so on.

Heavy fog will aggravate the condition of cardiovascular patients. This is because, on the one hand, the air pressure in dense fog is relatively low, people will feel irritable and their blood pressure will naturally rise. On the other hand, in foggy days, the temperature is often low. Some patients with hypertension and coronary heart disease suddenly go from warm indoor to cold outdoor, and blood vessels expand with heat and contract with cold, which will also increase blood pressure, leading to stroke and myocardial infarction. The air pollution is serious in foggy days, the fog is getting thicker in early winter, the air quality is poor, and the diabetic patients with poor resistance are very likely to have lung and trachea infections, which will aggravate the condition.

Fog warning signal

Yellow warning

Definition: Fog with visibility less than 500m may appear within 12 hours, or fog with visibility less than 500m and greater than 200m has appeared and will continue.

Precautionary guide: 1. The relevant departments and units shall, in accordance with their duties, make good preparations for fog prevention;

2, airports, expressway, ferry terminals and other units to strengthen traffic management to ensure safety;

3. Drivers should pay attention to the change of fog and drive carefully;

4. Pay attention to safety in outdoor activities.

Orange alert

Definition: Fog with visibility less than 200 meters may appear within 6 hours, or fog with visibility less than 200 meters and greater than or equal to 50 meters has appeared and may continue.

Precautionary guide: 1. The relevant departments and units shall, in accordance with their duties, do a good job in fog prevention;

2, airports, expressway, ferry terminals and other units to strengthen the dispatch and command;

3. Drivers must strictly control the speed of cars and ships;

4. Reduce outdoor activities.

red alert

Definition: Fog with visibility less than 50 meters may appear within 2 hours, or fog with visibility less than 50 meters has appeared and will continue.

Precautionary guide: 1. Relevant departments and units shall, in accordance with their duties, do a good job in anti-fog emergency work;

2. Relevant units shall take traffic safety control measures in a timely manner in accordance with industry regulations, such as suspension of aircraft take-off and landing at the airport, temporary closure of expressway, and temporary suspension of ferry service;

3. Drivers should take preventive measures in foggy days in accordance with the Regulations on Driving in Foggy Days, adopt reasonable driving methods according to environmental conditions, and find safe parking areas as soon as possible;

4. Don't engage in outdoor activities.