Understanding the background to wildfire hazards

Question 1

What does a fire require to start?

Answer 1

Fuel, Heat, Oxygen

Question 2

What is a growth fire?

Answer 2

Burning below the surface of the ground

Question 3

What is a surface fire?

Answer 3

Fire that burns loose debris on the surface, which includes dead branches, leaves, and low vegetation.

Question 4

What is a crown fire?

Answer 4

A fire that spreads from tree top to tree top

Question 5

What conditions favour wildfires?

Answer 5

Dry 
Hot
Windy 
Low humidity 
Fuels - certain plants are pyrophytic
Space between fuels

Question 6

What are the climatic conditions of wildfires?

Answer 6

Heatwave, Drought, Strong dry winds, Seasonal, El Nino/LOD, Global warming

Question 7

What are the fuels of wildfires?

Answer 7

Trees, Leaf Litter, Grass, Peat, Fire promoting vegetation - Eucalyptus tree, human built structures (wood)

Question 8

What impact do slopes have on wildfires?

Answer 8

“Fires on a 20% slope will advance at up to 4 times faster than one on flat ground”

Question 9

Why do “fires on a 20% advance at up to 4 times faster than one on flat ground”?

Answer 9

Because land and field upslope is pre-heated and therefore catches fire quicker

Question 10

When is the Harmattan season?

Answer 10

A season in the west-africana subcontinent which occurs between the ens of November and middle of march.

Question 11

What is the Harmattan season?

Answer 11

It is characterised by the dry and dusty northeasterly trade winds which blows from the Sahara’s desert over West Africa into the Gulf of Guinea

Question 12

Why does high moisture content prevent wildfires?

Answer 12

Prevents ignition and slows propagation

Question 13

Why are dense forests less susceptible to wildfires?

Answer 13

They provide more shade, resulting in lower ambient temperatures and greater humidity

Question 14

Why does less dense forests catch fire easily?

Answer 14

They contain less water than denser material such as branches and trunks

Question 15

How may evapotranspiration impact the carbon cycle?

Answer 15

Plants lose water through evapotranspiration, which is usually balanced by water absorbed into soil, humidity or rain. When this balance is not maintained, plants dry out and are therefore more flammable, often a consequence or droughts or wildfires (releases mass amount of carbon)

Question 16

What is a wildfire front?

Answer 16

The portion sustaining continuous flaming combustion, where unburned material meets active flames

Question 17

At what temperature is wood dried as water is vaporised?

Answer 17

100 degrees
The pyrolysis of wood releases flammable gases 230 degrees
Wood the smoulders at 380 degrees, and can ignite at 590 degrees

Question 18

At what temperature does the pyrolysis of wood release flammable gases?

Answer 18

230 degrees

Question 19

At what temperature does the wood smoulder (burn with smoke but no flame)?

Answer 19

380 degrees

Question 20

At what temperature does the woof ignite?

Answer 20

590 degrees

Question 21

What temperature can the flames of a wildfire heat the air in front too?

Answer 21

800 degrees through heat transfer from the wildfire front

Question 22

What are the Indian Ocean Dipole and El Nino?

Answer 22

Climate drivers

Question 23

What does the IOD refer too?

Answer 23

Year to year tropical sea changes in the Eastern Indian Ocean

Question 24

What are the three phases the IOD varies between?

Answer 24

Positive, neutral and negative

Question 25

How often does each phase occur?

Answer 25

Every three to five years on average

Question 26

When do positive or negative IOD phases occur?

Answer 26

During Autumn or winter

Question 27

When does a neutral IOD phase occur?

Answer 27

At the end of spring when the northern Australian monsoon arrives

Question 28

What happens during a neutral IOD phase?

Answer 28

Water from the Pacific flows between the islands of Indonesia, keeping seas to Australias northwest warm, air rises over this area and falls on the western side of the basin - little influence on climate

Question 29

What happens during a negative phase?

Answer 29

Westerly winds intensify, allowing warmer waters to concentrate near Australia, these stronger winds also it is harder for cool water to rise up from the deep near Indonesia, as warm waters move east the clouds follow bringing rain to Western Australia

Question 30

What happens during a positive phase?

Answer 30

Westerly winds weaken, and sometimes Easterly winds form, allowing warm water to shift towards Africa, South of Indonesia, these winds allow cold water to rise up from deep areas, with cooler waters and depending air in the Eastern Indian Ocean, less clouds form, less rain in central and southeast Australia

Question 31

What happens often but not always in Australia?

Answer 31

A positive IOD coincides with the drying influence on the El Nino in the Pacific, both drawing rainfall away from the Pacific

Question 32

What impacts does the a positive IOD phase coinciding with an El Nino have on Australia?

Answer 32

Failure of crucial winter spring rains and prime the land for severe summer fires seasons

Question 33

What else can occur at the same time?

Answer 33

A negative IOD with a El Nina

Question 34

What impacts does a negative IOD phase coinciding with an El Nina have on Australia?

Answer 34

Significant rainfall and widespread flooding

Question 35

When was the wettest year for Australia?

Answer 35

2010

Question 36

What is normally happening in the tropical pacific?

Answer 36

The Pacific receives normally easterly trade winds, pushing warm water nearer western side of the ocean near Asia and Australasia
On the east side of the pacific, as warm water gets pushed across, cold water is upwelled, creating a temperature difference across the pacific

Question 37

What does the El Nino essentially have?

Answer 37

Weakened or reversed trade winds

Question 38

What happens during El Nino?

Answer 38

Less water is pushed across the Pacific, this means the usually cold parts of the Ocean warm, changing weather patterns over the equatorial Pacific - increase in flooding in Peru and drought in Indonesia