OXYGEN-FUEL-HEAT KEY ELEMENTS OF BUSH FIRES

Wind also has a strong effect on the heat of a fire because it works like the bellows in a Blacksmith’s forge, blowing more oxygen into the fire, just like in the old days when people would use an old newspaper as a fan to get the kindling in the old wood stove going to boil the kettle and cook meals.

ADD HIGH WINDS TO THE THREE KEY ELEMENTS AND YOU HAVE A DANGEROUS SITUATION

   Huge Fire In NSW

 

 

 

 

 

 

 

 

 

 

These components have led to the development of the deadly trio of Fuel, Oxygen and Heat. Remove any one of these and fire will not be able to sustain itself. HEAT. Air temperatures have a direct influence on fire behavior

and has all the requirements for ignition and continuing the combustion process. Heat from the sun is transferred to the earth by radiation.  This heat warms up the surface of the earth and the atmosphere close to the surface is in turn warmed by heat reflecting from the surface. This is the reason that the temperature above the surface is cooler than at the surface of the earth. These temperatures generally decrease about 3.5 C degrees per thousand feet in altitude. This decrease is known as the adiabatic lapse rate. This is why climate scientists are divided on whether to continue with the unreliable method of modelling to estimate temperature or to use the wider coverage and reliability of satellites and  factor in the cooling bias.

Active Fires in NSW

Forest fuels receive heat by radiation from the sun.  As a result, less heat is required for ignition.  The differential heating of the earth’s surface is the driving force behind most of the influences on the atmosphere.  The sun emits short-wave energy rays (radiation).  When striking a solid object such as trees or grass, it is warmed.  The surface absorbs some of the heat and reflects some in long-wave radiation that is absorbed by the water vapor in the air thus raising its temperature as well.

At least fifteen percent of fires are lit by natural cause such as lightning and a further thirty five percent are accidental/careless.

WIND supplies extra OXYGEN which also assists combustion. Reduces fuel moisture and increases evaporation. Exerts pressure to move the fire, and the heat produced closer to fuel in the path of the fire increases radiation and blows embers ahead of the fire.

The stronger the wind blows the more it increases the supply of oxygen which results in the fire burning hotter and more rapidly and in the process prepares damp hazardous forest floor material for easy ignition by drying it out.

There are other problems with the wind, it can change speed and direction or become gusty. Wind can also influence the speed and intensity of a bush fire. High winds can cause the fire to crown into the top of the trees and jump fire breaks that would normally stop a fire. Wind can carry sparks ahead of the main blaze creating spot fires ahead of the blaze.

FUEL to BURN. The Australian bush, though it has a reputation for being dry and scrubby, varies greatly from place to place around the country. There are regions of open woodlands, grassland savannas, dense rainforest. A bushfire will burn anything that it finds in its path, but different types of vegetation burn differently. Generally, fuel is classified as being fine (grasses and twigs that are less than 6 millimetres in diameter) or heavy (branches, logs or stumps). Finer fuels burn more easily, feeding the spread of the fire, but heavier fuels burn with greater intensity, creating more heat and making the fire more difficult to put out.

4 Responses to “OXYGEN-FUEL-HEAT KEY ELEMENTS OF BUSH FIRES”

  1. Talford says:

    The Guardian newspaper says that hazard reduction burning had little to no effect in slowing the most severe fires that devastated more than 5m hectares across New South Wales this summer, an analysis has found.
    Forest scientists from the University of Melbourne said initial results suggested hazard reduction was best used in a targeted way around assets to help protect them from less intense fires.

  2. Peter Shannon says:

    You could add drought as a factor but I guess that comes under the nature of dry fuel. We spent Christmas in the Strathbogie ranges. I cannot remember having seen the country so dry as it is today with a lot of dead trees everywhere. There was no area spared in the 1939 fires which burnt out most of the area and killed a lot of livestock.

  3. Adam says:

    When it was announced that Michael Mann would appear on Q & A regarding we promptly switched off.
    His Hockey Stick Graph succeeded in having the IPCC remove The Little Ice age and the Medieval Warming Period, despite ice core evidence to the contrary, from all its future reports.

    The clear implication was that the earth had had a benign and unchanging climate for about a thousand years, and now humans had entered the picture with their fossil fuels and were rapidly destabilizing the situation.

  4. John Wilson says:

    If Paul Barry wants a bone to chew on he need look no further than the Paris Accord where only a handful of countries, including Australia, are honoring their pledges.
    Russia have ditched their plan, due to pressure from industry, Japan and China have increased their reliance on coal fired power. Saudi Arabia have not submitted a plan and are too busy developing the Maldives. China have pledged to do nothing about emissions until 2030 by which time its growth would have leveled off anyway.

    Oren Cass, a senior fellow at the Manhattan Institute, has rated it as somewhere between a farce and a fraud describing “the agreement” as countries being allowed to send in any commitment they wanted on a piece of paper, which were then stapled together and described as an “amazing” achievement.

    “India made no pledge to limit emissions at all. They pledged only to become more efficient. But they proposed to become more efficient less quickly than they were already becoming more efficient. So their pledge was to slow down.”
    “My favorite was Pakistan, whose pledge was to ‘Reach a peak at some point after which to begin reducing emissions,’” says Cass. “You can staple those together, and you can say we now have a global agreement, but what you have is an agreement to do nothing.” ..amazing!

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