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SOEE3760 > Fire > Flashcards

Fire Flashcards

1
Q

What feedbacks do fires affect?

A
  • Biogeochemical cycles
  • Vegetation composition and structure
  • Land-atmosphere water and heat exchanges
  • Atmospheric chemistry and composition
  • Human health and property
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2
Q

What do fires depend on?

A
  • Vegetation characteristics
  • Climate
  • Human activities
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3
Q

Give 2 examples of major wildfire events

A
  • 2019-2020 Australian bushfires
  • 2015 - Southeast Asian Haze - likely due to strong 2015 El Nino - caused drier-than-usual conditions
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4
Q

Why is it difficult to observe fires?

A
  • Due to high temporal and spatial variability in emissions
  • Difficulties involved in conducting measurements in remote forested regions

So observations are predominantly taken using satellites

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5
Q

What are polar satellites - what are strengths/weaknesses?

A

Most fire estimates are based on polar satellites

Strengths:
- Global coverage
- Frequency of global coverage depends on scan width
- Higher spatial resolution - moderate (1km) - MODIS / High (30m) - Landsat/ASTER

Weaknesses:
- Fewer opportunities for cloud-free observations
- Time resolution - 4 per 24 hours for MODIS Terra/Aqua
- Temporal sampling issues related to diurnal fire cycle

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6
Q

What are the two types of satellites used to observe fires?

A
  • Polar
  • Geospatial
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7
Q

What are the strengths and weaknesses of geospatial satellites?

A

Strengths:
- Hemispheric fire monitoring
- Near real-time data for fire management
- Few/no temporal sampling issues related to diurnal fire cycle
- Broad Direct Broadcast capability

Weaknesses:
- Gaps in global spatial coverage
- Spatial biases in envelope of detectable fires

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8
Q

Where are most fires throughout the year?

A
  • December - Mainly Africa
  • April - mostly agricultural fires in southern Russia
  • July - southern hemisphere - tropical africa
  • September - African fires + south america - Amazon - big fire season
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9
Q

What is the GFED and what does it provide?

A

Global Fire Emissions Database
- Combine satellite observations with models
- Provide global pictures - estimate emissions
- Emission = Fuel consumption x burned area x emission factor
- Provide info on CO, NOx, VOCs, aerosols etc
- Can provide average carbon emissions from fires - e.g., 2017 - 2.2 PgC/year
- Can also show what types of fires contribute the most

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10
Q

What types of fires dominate contribution to fires?

A
  • Grassland and savannahs are largest contributors : 44%
  • Deforestation have substantial contribution
  • Peat fires are most variable - coefficient of variation - 176%
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11
Q

What is GFAS, and what does it do?

A

Global Fire Assimilation System
- Uses fire radiative power (FRP) satellite observations to produce daily estimates of wildfire and biomass burning emissions
- Slight decline overtime - potentially due to land use change - declining savanna fires
- Fires in amazon and Europe increasing

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12
Q

What does fire activity require?

A
  • Biomass resources to burn
  • Atmospheric conditions conducive to combustion - dry, hot, windy
  • Ignitions - e.g., lightning/human-caused patterns

All 3 affecred by climate in complex ways - over multiple timesclaes

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13
Q

How have fires in Europe been affected by climate?

A

e.g., 2017 fires in Portugal, France, Italy, Croatia
Caused by:
- Increased temperatures have:
- Extended traditional wildfire season
- Increased the frequency of blazes

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14
Q

How do we try and predict fires in the future and what are the largest sources of uncertainty?

A

Use models:
- Try and predict how fires will change depending on the change of climate factors in future
- E.g., 16 models ensemble mean change and agreement - Moritz et al., 2012
- But large uncertainty - signal to noise ratio - need signal to be stronger
- Largest source of uncertaintly is precipitation - how this will evolve in future years - temperature also a large uncertainty

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15
Q

What is predicted about fires for the end of the century?

A

By end of century, likelihood of catastrophic wildfire events will increase by factor of 1.31 to 1.57
- Due to more favourable conditions for fires in future climate

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16
Q

How can humans affect fires? + / -

A

Start:
- Fire ignition
- Agricultural burning
- Deforestation / land changes

Stop:
- Fire suppression
- Fragmentation of fuel load - through road building, agriculture etc

17
Q

How can humans use fires for agriculture - e.g., MODIS in indonesia?

A
  • Most fires timed with land cover change - fire used to clear forests
  • Little fires in years before land cover change - natural forest has little fire
  • Fires after forest loss due to agricultural use

Indicates fires are used to manage regions - to clear land for new agricultural plantations

18
Q

How can fires affect humans?

A
  • Particulate matter < 2.5 micrometres - PM2.5
  • Can cause adverse health affects - respiratory/heart problems
19
Q

How has wildfire deforestation rate changed in Brazil over time and how has this affected human health - study method?

A
  • Reddington et al., 2015
  • Atmospheric model and GFED3 emissions to quantify PM2.5 concs from fires and impact on human health
  • 40% reduction in Brazils deforestation rate estimate to prevent ~1060 premature mortalities annually over South America
  • Opposite case in Indonesia - more deaths associated with poor air quality
20
Q

What is the Brazilian Cerrdo and how has it been affected by fires?

A
  • Cerrado is Brazilian tropical savanna - covering ~2 million km^2
  • Considered most botanically diverse savanna
  • Biodiversity hotspot
  • Only 3% of original area is protected
  • Historically accounts for more than half of Brazil’s annual burnt area
  • 60% of all fires come from savannas
21
Q

How do fires affect radiation regime?

A
  • Fire emissions include aerosols - very small particles suspended in air
  • They affect solar radiation through: Scattering and Absorption
  • Observed that they produce reductions in radiation comparable to those resulting from persistent cloud cover
  • The net effect on photosynthesis of radiation changes depends on a balance between the reduction in total radiation and increase in its diffuse fraction
  • So with diffuse radiation - trees at top receive slightly less radiation, but trees in shade will gain much more GPP - more photosynthesis
  • Overall: more diffuse radiation - increases total photosynthesis and GPP
22
Q

What was found about fires and plant productivity in the Amazon?

A
  • Due to fires = more diffuse radiation = more efficient photosynthesis = higher GPP/NPP
  • Effects offset 30-60% of Amazon biomasss burning carbon emissions
  • Accounts for 8-16% of the observed Amazon carbon sink
  • Rap et al., 2015

SOEE3760 (12 decks)

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