Weather of Arabia - Forest fires may ignite within seconds, spreading quickly and devouring dry plants and almost everything in their path, as forest fires can sweep thousands of hectares of surrounding land, threatening the homes and lives of many in the vicinity, even producing smaller fires by throwing Embers are miles away. In this article we'll look at wildfires, explore how they start, and how weather contributes to their spread.
On a hot summer's day, when drought conditions are peaking, something as small as a spark from a train wheel hitting the track can start a wildfire. Sometimes, fires occur naturally for a variety of reasons, including the heat of the sun or lightning. However, the majority of wildfires are caused by human negligence.
Common human causes of wildfires include:
Everything has a certain ignition point, the temperature at which wood ignites (300 degrees Celsius), when wood is heated to this temperature, it releases hydrocarbon gases that mix with oxygen in the air and ignite and create a fire.
There are three components necessary for ignition and combustion to occur, called the fire triangle, as fire requires:
Firefighters often talk about a fire triangle when they are trying to put out a fire. If they can remove any of the sides of the triangle (fuel, oxygen, or heat), then they can control the fire and eventually extinguish it.
After an ignition has occurred and a fire has started, there are several factors that determine how a fire will spread. These three factors include; Fuel, weather and terrain . Depending on these factors, a fire can quickly die out or turn into a raging fire that burns thousands of hectares.
Forest fires spread depending on the type and amount of fuel surrounding them. Fuels can include everything from trees, plants, and dry grass fields to homes. Here are the basic fuel properties that determine how it affects a fire:
Small materials such as: dry grass, pine needles, dry leaves, dead branches, etc., burn faster than large tree trunks and broad branches.
Weather plays a major role in the birth, growth and death of wildfires, with drought leading to very favorable conditions for wildfires, and winds helping to advance wildfires.
Weather can stimulate fire to move faster and swallow more land. It can also make the task of fighting a fire more difficult.
There are three components of weather that can affect wildfires:
1. Temperature: Temperature affects the outbreak of forest fires, because heat is one of the three corners of the fire triangle that we mentioned earlier. The remains of trees and plants on the ground receive heat from the sun, which heats and dries materials. Warmer temperatures allow the fuel to ignite and burn faster, increasing the rate of wildfires. For this reason, wildfires tend to flare up in the afternoon, when temperatures are at their highest.
2. Winds: Winds have perhaps the greatest influence on the behavior of wildfires, and are also the most unpredictable factor. Wind supplies the fire with additional oxygen, drying the materials further and pushing the fire across the earth at a faster rate.
Winds not only affect how a fire starts, but the fires themselves can develop their own wind and weather patterns. Large, violent wildfires can generate winds called fire whirlpools. Fire whirlpools, which resemble tornadoes, are caused by the heat of a fire, and fire whirlpools are known to hurl flaming tree trunks and burning debris into great distances.
The stronger the wind blew, the faster the fire spread. The fire generates its own wind ten times faster than the surrounding wind, and it can even throw embers into the air and create additional fires. Winds can also change the direction of the fire, and storms can raise fires to trees, resulting in crown fires reaching even the tops of the trees.
3. Humidity: While wind helps spread fire, moisture works against fire. Moisture (in the form of dampness or precipitation), can slow a fire and reduce its intensity. Materials can be difficult to ignite if they contain high levels of moisture, because moisture absorbs the heat of a fire. When the humidity is low, which means there is little water vapor in the air, wildfires are more likely to start. The higher the humidity, the less likely the material will dry out and catch fire.
Since humidity can reduce the chances of wildfires breaking out, precipitation has a direct impact on fire prevention.
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