What should I pay attention to in lightning weather?

1, natural phenomenon

What is lightning?

Lightning is a spectacular and somewhat frightening discharge phenomenon accompanied by lightning and thunder. Lightning is usually produced in cumulonimbus clouds with strong convection, so it is often accompanied by strong gusts and heavy rains, and sometimes accompanied by hail and tornadoes. The top of cumulonimbus clouds is generally very high, up to 20 kilometers, and there are often ice crystals on the top of the clouds. The attachment of ice crystals, the breaking of water droplets and air convection make clouds generate charges. The distribution of charge in the cloud is complicated, but generally speaking, the upper part of the cloud is dominated by positive charges and the lower part is dominated by negative charges. Therefore, a potential difference is formed between the upper and lower parts of the cloud. When the potential difference reaches a certain level, discharge will occur, which is our common lightning phenomenon. The average current of lightning is 30,000 amps, and the maximum current can reach 300,000 amps. The voltage of lightning is very high, about 1 billion to 1 billion volts. The power of medium-intensity thunderstorm can reach10 million watts, which is equivalent to the output power of a small nuclear power plant. In the process of discharge, due to the sudden increase of temperature during flashover, the air volume expands rapidly, resulting in shock waves and strong lightning. When the charged Lei Yun is close to the protrusions on the ground, a violent discharge will occur between them. There will be strong flash and explosion roar at the scene of lightning discharge. This is the lightning and thunder that people see and hear.

What is lightning?

Storm clouds usually produce charges, with negative charges at the bottom and positive charges at the top. They also produce positive charges on the ground, which move around with the clouds. Positive and negative charges attract each other, but air is not a good conductor. Positive electricity rushes to treetops, hilltops, tall buildings and even above the human body, trying to meet negative clouds; Dendritic tentacles with negative charges extend downward and get closer to the ground. Finally, the positive and negative charges finally overcome the air barrier and connect. A huge current rushed from the ground to the clouds along the conductive path, producing a bright flash. The length of lightning may be only a few hundred kilometers, but it may also be several kilometers long.

The temperature of lightning varies from 17000 degrees Celsius to 28000 degrees Celsius, which is 3~5 times the surface temperature of the sun. The extreme heat of lightning caused the air along the way to expand violently. Air moves very fast, so waves are formed and sounds are made. When lightning approaches, you hear a sharp crack; If it's far away, you hear rumbling. You can start the stopwatch after you see the lightning, press the stopwatch to stop when you hear the thunder, and then divide the number of seconds by 3 to get a rough idea of how many kilometers the lightning is from you.

Types of lightning

Ordinary lightning with twists and turns is called dendritic lightning. If the passage of dendritic lightning is blown to both sides by the wind, so that it seems that there are several parallel lightning, it is called strip lightning. If two lightning branches seem to reach the ground at the same time, they are called bifurcated lightning.

When lightning flashes between the negative and positive charges in the cloud, making the sky in the whole area bright, it is called sheet lightning.

Lightning that does not reach the ground, that is, lightning within the same cloud or between two clouds, is called cloud-to-cloud lightning. Sometimes this lightning will travel a long distance and land on the ground many kilometers away from the storm. This is called a "bolt from the blue".

The electric action of lightning sometimes forms a halo-like red light around tall and sharp objects. Usually in stormy seas, red light can be seen around the mast of a ship, so people borrow the name of the patron saint of sailors and call this lightning "the fire of St. elmo".

Super lightning refers to those rare lightning whose power exceeds ordinary lightning 100 times. The electricity generated by ordinary lightning is about 1 megawatt, while the electricity generated by super lightning is at least 1 megawatt, and may even reach trillions to 1 megawatt.

Clock Island in Newfoundland was obviously struck by a super lightning at 1978. Even the houses at 13 km away rattled, and the windows and doors of the whole village were sprayed with blue flames.

The time of the attack

When you read this article, there are about 1800 lightning exchanges going on all over the world. They emit about 600 lightning flashes per second, of which 100 hits the earth.

Lightning can transform some nitrogen in the air into nitrogen compounds, which can be washed to the ground by rain. In a year, every hectare of land on the earth can get a few kilograms of this free fertilizer from the sky.

Kampala, the capital of Uganda, and Java, Indonesia are the most vulnerable places to lightning strikes. According to statistics, there are 300 days of lightning in Java a year. The most violent lightning in history was that 1975 hit a small house near Umtali in rural Zimbabwe, when 2 1 person died.

The harm of lightning

More than two-thirds of lightning victims were attacked outdoors. Two thirds of the people survived. Among the people killed by lightning, 85% are men, and most of them are between 10 and 35 years old. Most of the dead hid from lightning and rain under trees.

Sullivan may be the champion who was struck by lightning. He is a retired forest manager who was struck by lightning seven times. Lightning once scorched his eyebrows, his hair, his shoulders, ripped off his shoes and even threw him out of the car. He said simply, "Lightning will always find me."

The harm of lightning to human body includes the direct action of current, overpressure or electric power and high temperature. When a person is struck by lightning, the current will pass through the human body quickly. In severe cases, it will lead to heartbeat, respiratory arrest and brain tissue hypoxia and death. In addition, when lightning strikes, sparks will be generated, which will also cause different degrees of skin burns. Lightning injury can also cause dendritic lightning stripes, epidermal peeling, intradermal bleeding, eardrum or visceral rupture.

Lightning protection description

The lightning current generated when lightning occurs is the main source of harm, and its harm includes direct lightning strike, induced lightning strike and intrusive lightning guided by overhead lines. For example, overhead lines used in various lighting, telecommunications and other facilities may introduce lightning into the room, so strict preventive measures should be taken.

A, vulnerable to lightning.

1. Tall buildings, storage tanks, etc. Lack of lightning protection devices or unqualified lightning protection devices;

2. The metal roof is not well grounded;

3. Buildings and trees in wet or open areas;

4. Due to the conductivity of flue gas, chimneys are particularly vulnerable to lightning strikes;

There is a radio in the building, but there is no lightning arrester and no good grounding.

Second, the methods to prevent lightning strikes

1. Lightning protection device is installed on the building. That is, lightning protection devices are used to introduce lightning current into the earth and then disappear.

2. During a thunderstorm, people should not go near high-voltage distribution rooms, high-voltage wires and isolated tall buildings, chimneys, poles, trees, flagpoles, etc. Not to mention standing in an empty highland or under a big tree to shelter from the rain.

3. You can't use umbrellas with metal columns. Do not use metal tools, such as crowbars, when working in the suburbs or in the open air.

4. Don't wear wet clothes near or stand on metal objects in the open air.

Don't turn on your mobile phone at the top of the mountain in thunderstorm weather, let alone use it.

6. Don't touch and approach the grounding conductor of lightning protection device in thunderstorm days.

7. In a thunderstorm, leave lighting lines, telephone lines, TV lines and other lines indoors to prevent lightning from infringing on people and being hurt.

8. When it thunders and rains, it is forbidden to stay at the top of the mountain or in hilly areas. More importantly, it is forbidden to continue to push up the rain scene. Don't hide under big trees or near telephone poles, and don't walk or stand in open fields. You should hide in a low-lying place as soon as possible, or try to find a room floor or a dry cave to escape.

9. In thunderstorm weather, don't use an umbrella with a metal handle, and take off glasses, watches and belts with metal frames. If you travel by bike, you should leave the bike as soon as possible and stay away from other metal objects to avoid being struck by lightning.

10. Don't go swimming, boating or fishing in rivers and lakes in thunderstorm weather.

1 1. In case of lightning, thunder and rainstorm, visitors should immediately turn off the indoor TV, tape recorder, stereo, air conditioner and other electrical appliances to avoid using electricity. It's safer in the middle of the room when it thunders. Don't stay under the electric light, and don't lean against posts, walls, doors and windows, so as to avoid accidents caused by induced electricity when it thunders.

When lightning strikes, the traveling companion should take the patient to the hospital immediately. If breathing and heartbeat have stopped at that time, mouth-to-mouth resuscitation and chest massage should be carried out at the scene immediately, and on-site rescue should be actively carried out. Don't rush to the hospital without rescue, otherwise it will delay the onset and lead to death. Sometimes, on the way to the hospital, we have to continue artificial respiration and chest massage. In addition, we should pay attention to keep patients warm. If you have mania, convulsions, convulsions and other mental symptoms, you should also do a cold compress on your head. For the part of electric burn, in the case of first aid, it is only necessary to keep it dry or bandage it.

During a thunderstorm, even if a lightning rod is installed, it is necessary to quickly unplug the indoor TV, refrigerator and antenna power supply to prevent unnecessary losses caused by space electromagnetic interference. In addition, judging from the formation and occurrence process of lightning, lightning accidents mostly occur in open fields, the tops of buildings, tall trees, rivers, lakes, ponds and wet areas.

Wang Hongmin, member of the National Technical Committee for Standardization of Building Electrical Devices: Outside, we should consider the lightning activity area and see the distance of lightning activity. Generally, we can judge the distance by listening to thunder. Don't hide under lightning rods and trees. Don't open an umbrella in an open place, because the umbrella has a needle tip and the electric field intensity should be concentrated. Don't use your mobile phone in an open place. Squat down and put your feet together.

Experts finally stressed that in case of thunderstorm, citizens had better hide in buildings with metal doors and windows or lightning rods. The car with metal body is also the best "lightning protection place". Once these buildings or cars are struck by lightning, their metal frames or lightning protection devices or the metal itself will lead lightning current into the ground.

The concept of lightning statistics

The number of thunder and lightning-when the thunderstorm is going on, the rumble of thunder continues. If the time interval of thunder is less than 15 minutes, no matter how long the thunder spreads intermittently, it is counted as a thunderstorm; If the lightning stop time is longer than 15 minutes, it is divided into two thunderstorms.

Lightning hour-that is, there is a thunderstorm within astronomical hours, or more generally, thunder is heard during this time, regardless of the duration of the thunderstorm. The "annual lightning hours" in a certain area refers to how many astronomical hours of thunderstorms have occurred in that area in a year, regardless of whether the thunderstorm lasted for a whole hour or only a few minutes in a certain hour.

Thunderstorm day-also known as lightning day. This is what we are most familiar with. As long as there are thunderstorms and thunder on this day, no matter how long the thunderstorm lasts, it is counted as a lightning day. "Annual Lightning Day" is equal to the sum of annual lightning days.

Thunderstorm month-also known as lightning month-means there will be thunderstorms this month. "Thunderstorm months per year" refers to how many months in a year there are thunderstorms.