Lightning can be a powerful wildfire trigger.
For every 10,000 lightning strikes in northern North America, between two and five will spark a forest fire.
A new study found that weather conditions play a major role in which strikes spark a fire.
Researchers studied lightning and rain data between 1987 and 2020 in Central and Northern California, an area where fires are a significant issue. They found that almost half (46%) of lightning strikes occurred on days with less than 2.5 millimeters of rain - dry enough to be considered “dry lightning.”
1. High Temperature
The heat that can be generated by lightning strikes is one of the primary factors driving wildfires. These lightning-caused fires are a big concern for people who live in areas of the country where climate change is already affecting weather patterns.
As the planet warms, it's expected that wildfires will grow in size and frequency. In fact, lightning strikes that can start wildfires are expected to increase 12% for every degree Celsius of global warming and about 50% over the 21st century if we keep burning fossil fuels at the current pace.
These lightning-caused fires can occur anywhere on the planet, but the West is particularly prone to them because it has been increasingly dry for decades. A recent study found that the number of lightning-caused fires in that region increased by a third between 1992 and 2015.
Most lightning-caused fires are easy to identify because of weather radar and satellite data, but sometimes the onset of a fire can be days after the initial strike. This is because small embers can smolder and produce more heat. If this happens, it's called a "positive feedback loop" and can lead to further fires if they're not treated right away.
According to scientists, the most likely way that a lightning strike can ignite a wildfire is by striking a dry spot of ground or vegetation. As the weather gets drier, it's not uncommon for lightning to strike during a thunderstorm when little to no rain is expected, which can make the air more conducive to fires.
That's why it's important to have a good understanding of where lightning is more likely to strike and when. That can help firefighters plan how to attack a blaze and what kind of resources they'll need to battle it.
As global temperatures rise, it's also expected that a growing number of lightning-caused fires will occur in the boreal forests and Arctic tundra. These are areas where the air is much drier than it has been in recent decades and where climate change is expected to cause lightning strikes to become more frequent.
2. High Pressure
A high pressure system is a weather pattern that results when air converges at higher altitudes. This creates a large amount of air space that is not filled by water vapor. It can also inhibit cloud formation and precipitation.
In contrast, low pressure systems occur when air converges near the ground. This causes water vapor to rise and cool. As it does, it condenses into small water droplets or ice crystals that can form clouds and precipitation.
These clouds can be a nuisance, causing smog and pollution. They can also create conditions that are conducive to wildfires.
Moreover, high pressure can lead to thunderstorms. Storms can increase wind speed and intensity, which can cause fires to spread rapidly.
Lightning can also cause a wildfire to begin if it strikes a tree or other structure that has flammable materials on it. However, these fires can sometimes be prevented if the lightning strike is short and only lasts for a few milliseconds.
Some scientists have found that the likelihood of lightning-ignited fires increases as a result of climate change. This is because of the heat transfer from lightning to combustible materials.
Scientists have found that fires in parts of the world with warmer temperatures and drier soils are more likely to start due to lightning. They have identified several regions that are most at risk for these types of fires: Australia, South America, Southeast Asia and North America.
The research team studied lightning data and compared the type of lightning that caused wildfires with those that did not. They found that 90% of wildfires they examined started because of hot lightning strikes.
They also discovered that these lightning strikes typically lasted longer than the average. These long lightning strikes transfer more heat to combustible materials than those that last less than 40 milliseconds.
The research team also found that fires are most likely to start when the lightning and other weather and fuel conditions interact. The research team suggests that more fires will likely occur in areas with high temperatures and drier soils as climate change occurs.
3. Dirty Air
Lightning can spark wildfires that are especially bad for the environment. The air around the fire can be filled with ash, soot and other pollutants that can clog the airways.
These air particles, called particulates, are too small to see but can be toxic. They can cause asthma, respiratory disease and other health problems.
In some countries, the smoke produced by fires can be as bad for the air quality as the pollution produced by cars and factories. It is especially dangerous for people with lung conditions or who have young children.
Fortunately, scientists have found ways to reduce the harmful effects of air pollution from wildfires by deploying technology that captures and disposes of these particles as they pass through the atmosphere.
One way to do this is with a device called an aerosol injection unit. This is similar to a fog machine, but it uses electricity instead of water to blow a mist over the air.
Another way to get rid of dirty air is to replace the air filter in your car. This can be done on your own or with the help of a mechanic.
The most important thing to know about dirty air is that it can reduce your car's downforce, which is the amount of force your tyres push against the road. This reduces your grip and can throw you off course, especially if you're not in the lead.
Dirty air can also cause your tyres to overheat, which can eventually damage them and cause you to puncture.
You can see the effect of this in Formula 1 races. F1 drivers often complain about the turbulence that their cars produce in the track, which can make them lose control and get into crashes.
Luckily, there are many things we can do to reduce the chances of having a fire caused by lightning. In fact, a new study has shown that if we improve our air quality, we can reduce the number of lightning-caused wildfires by up to 40%!
4. Long Stroke
In a normal lightning flash, each time an electrical charge moves through the channel from the cloud to the ground it is called a stroke. Often, this happens several times per flash. This is called "multiplicity."
The shortest distance between the cloud and the ground is about one mile, but in most cases, this distance can be quite long. This is why lightning can be seen from the sky in long arcs, or streaks.
It is these long arcs that are more likely to hit the ground and ignite a wildfire. They can be particularly destructive in areas where the weather is hot and dry.
These types of arcs are often accompanied by little to no rain, which is why researchers are especially concerned about the fires that have burned in California this year. They have been sparked by a type of lightning known as "dry lightning."
When the air temperature is too hot and dry, lightning is more likely to strike the ground than it would be if the air had moisture, and this can char the vegetation in its path. In fact, the recent megadrought that plagues the West has led to more and more dry lightning, which is why the region experienced an unprecedented amount of wildfires this summer.
Scientists found that the five biggest fires this summer in California were sparked by dry lightning. These blazes were mainly located in coastal ranges that were unaccustomed to such electrical storms.
The researchers said the lack of rain made the strikes more powerful, and this helped to set off fires that were difficult to control. They said this was an important finding because it can help firefighters determine where to fight fires.
While lightning isn't the only cause of wildfires, it's the most common and has an outsized impact in kicking them off. Many experts agree that it's one of the most dangerous ways a fire can start.
A new study from the University of California, Berkeley and Stanford University has found that some of the largest wildfires in the state were sparked by lightning. The most prominent of these was the 2020 August Complex, which burned more than a million acres.