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  • Forest Fires: Particulate Effects on Global Climatology

    Akua Asa-Awuku, Christos Fountoukis, & Robyn Williams

  • SummaryI. IntroductionWhat are aerosols?How are clouds formed?What is the direct/indirect effect (IPCC) chartTropospheric EffectsSemi-direct effectAmazon data on cloud coverageAmazon pictures and articleStratospheric EffectsConclusions

  • Biomass BurningWildfires consume a million or more square kilometers per year. Fire is a tool used in agriculture to clear croplands and help return nutrients to the soil. Annually, humans burn anywhere from 750,000 to 8.2 million square km of forest and grassland around the world.It is expected that a surface warming trend at high northern latitudes will lead to an increase in boreal fires and their effects, such a trend toward increased burning has already been detected (Stocks et al., 1998)

  • Forest Fires emit Aerosolssuspension of a fine solid or liquid particles in gas. PrimarySecondary

  • Clouds significantly reflect incoming Solar Radiation

    J.T. Houghton: The science of climate change

  • Not Just Water VaporMany areas of the globe with high water vapor concentrations do not form clouds

  • Why are clouds linked to aerosols?Clouds form in regions of the atmosphere where water vapor is supersaturated.Water vapor supersaturation is generated by cooling (primarily through expansion in updraft regions and radiative cooling).Cloud droplets form from pre-existing particles found in the atmosphere (aerosols). This process is known as activation. Aerosols that can become droplets are called cloud condensation nuclei (CCN).

  • Changing Cloud PropertiesDirect EffectIndirect EffectThe radiative properties are highly complex (and poorly understood).

  • The Indirect Effect The crushed smaller particle ice, reflects more than the larger ice particles

  • What is the Impact?

  • Forest Fire EffectsTroposphericStratospheric Differences

  • Semi-direct effectReduction in cloud coverWarming of the surfaceIn the morning: heating of the atmosphere, cooling of the surface (increased static stability, supressed convection)In the afternoon: less cloud cover, more sunlight in the surface

  • Heavy smoke chokes clouds

  • Decreased cloud cover

  • NASA MeasurementsTotal amount of light reflected through the top of the atmosphereArea covered by clouds and by smokeOptical thickness of smokeMeasurements in meteorologically different regions

  • NASA ResultsMuch less solar energy reflected back up to the space with the reduction in cloud coverSmoke chokes off cloud formation rather than being a reflector of sun lightSimilar examples in Africa and CanadaGlobal cooling influence of aerosols smaller than previously thoughtThe semi-direct effect amounts to a reduction in global annual mean cloud cover and LWP of 0.2% and 0.3g/m2, respectively

  • Stratospheric EffectLong Lifetime and Distance

    Unknown Degree of Prevalence

    Fromm and Servranckx Study

  • Smoke Particulate TransportTropopauseVertical Transport InhibitorWell Mixed Tropopause vs. Very Stable Stratosphere

  • Smoke Particulate TransportVolcanoes

    Nuclear Winter

    Supercell ConvectionBoreal Fire - Summer of 1998

  • Supercell ConvectionHighly organized thunderstormExtremely strong rotating updraftAbility to produce severe weather

  • Case Study: Chisholm Fire

    28/29 May 2001

    160km North of Edmonton, Alberta

  • Pre-Convection

  • Early Stage of Convection

  • Fully Developed Convection

  • Post-Convection

  • Case Study: Chisholm FireDynamic Relationship Between Fire and ConvectionSurface Heating Destabilization of AirGeneration of wind and lighteningAggravation of existing fires Supercell StormsIntense Interfacial Gravity Waves

  • Case Study: Chisholm FireTransport from planetary boundary layer to upper troposphere/lower stratosphere

    1998 Substantial Statospheric Aerosol Increase

  • Conclusions: Semi-Direct Effect

    In highly polluted regions: increase of BC causes a reduction of LWP and cloud coverHowever, indirect effect causes the oppositeTherefore, all aerosols radiative effects should be calculated simultaneously in order to determine the net increase/decrease of cloud cover and LWP

  • Conclusions: Stratospheric Effect

    Volcanic Haze Effect

    Material Distribution with a radiative, chemical, and cloud impact

  • Where Do We Go From Here?Unknown Extent Quantify

    Increased Urgency of Increased Fire Prevention Methods

  • Questions?

    -recognized unusual stratospheric aerosols