Dust ImpactsDirect and indirect climate forcingRegional impacts on temperature and hydrological cycleDust as micro-nutrient fertilises marine and terrestrial ecosystemsNeutralisation of acid rain, atmospheric chemistryTransport medium for bacteria, fungi, and pesticidesCoral bleachingHuman healthEconomyReduced visibility (aviation, ground transport, solar energy, ...)Limited reliability of electronic devices

Dust ImpactsDirect and indirect climate forcingRegional impacts on temperature and hydrological cycleDust as micro-nutrient fertilises marine and terrestrial ecosystemsNeutralisation of acid rain, atmospheric chemistryTransport medium for bacteria, fungi, and pesticidesCoral bleachingHuman healthEconomyReduced visibility (aviation, ground transport, solar energy, ...)Limited reliability of electronic devices

Atmospheric Dust Cycle[www.geo.cornell.edu ]EmissionTransportDeposition

Dust Climate InteractionsDust EmissionDust in suspension,Mauritania[www.lmfa.ec-lyon.fr]

Dust Climate InteractionsDust EmissionAirborne Dustdust uplift

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust Depositionsettlement

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust Depositionsettlement

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperature

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperature

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperatureradative forcing

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperatureradative forcingcloud properties,precipitation

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperatureradative forcingcloud properties,precipitationBio-productivity(marine, terrestrial)

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperatureradative forcingcloud properties,precipitationBio-productivity(marine, terrestrial)CO2 sink

Dust Climate InteractionsDust EmissionAirborne Dustdust upliftDust DepositionsettlementAtmosphereWind,clouds, precipitationtemperatureradative forcingcloud properties,precipitationBio-productivity(marine, terrestrial)CO2 sink

Towards understanding the Role of Dust in Climate ChangeDescribe the amounts and geographic distribution of mineral dust fluxes (models/remote sensing).

Quantify the direct radiative forcing effects of a realistic dust field and the resulting impacts on climate.

Assess the impact of increased dust input on marine productivity.

Towards understanding the Role of Dust in Climate ChangeDescribe the amounts and geographic distribution of mineral dust fluxes (models/remote sensing).

Quantify the direct radiative forcing effects of a realistic dust field and the resulting impacts on climate.

Assess the impact of increased dust input on marine productivity.

Energy BalanceIPCC report, 2007

Radiative ForcingGreenhouse gases as carbon dioxide warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the Earths surfaceBackscattering of incoming sunlight by aerosol particles partly offsets this warmingSoil dust aerosol is a major part of the atmospheric aerosol loadIPCC report, 2007

Dust Radiative ForcingExtinction efficiencyLight absorption and scattering per particle

Single scattering albedoRatio of light scattering to light extinction

Asymmetry parameterFraction of forward scattered light

Parameters depend on particle size, mineralogical composition, and particle shape !

Direct Radiative Forcing

Direct Radiative ForcingPositive effect over bright surfaceNegative effect over dark surfaceTakemura et al., 2009Direct radiative forcing: difference in radiative budget between including and excluding dust aerosol within the same simulationPositive due to dust layer over-iding low-level maritime clouds

Direct Radiative ForcingChange in temperature due to dustNegative feedbackreduced surface windsenhanced atmospheric stabilityreduced dust emissionReplicates dust radiative forcing patternsIndicates complex interactionsDJFJJAGISS model simulation, I. Tegen

Dust Radiative ForcingFor individual cases:Reduction in surface temperature much strongerUp to 12C for March 2006 case [Tulet et al., 2007, Cavazos et al., 2009, Mallet et al., 2009]Disturbed diurnal cycle for surface temperature

Enhanced atmospheric stabilityDust layer as second heat sourceNegative feedback on dust emissionTulet et al., 2008pot. temperature

Indirect Dust EffectDust, and aerosol particles at all, can interact with clouds modify their properties and ultimately their radiative effectSeaWiFS

Aerosol Cloud InteractionsIPCC report, 2007Indirect effect: aerosol-cloud effect

Aerosol Cloud InteractionsHoose et al., 2008

Aerosol Cloud InteractionsHoose et al., 2008

Dust triggering Droplet FreezingDroplet freezing at -38C < T < 0CMain mechanism:

Importance of indirect dust-cloud effect is still unclear!image: http://www2.chem.ubc.ca

Towards understanding the Role of Dust in Climate ChangeDescribe the amounts and geographic distribution of mineral dust fluxes (models/remote sensing).

Quantify the direct radiative forcing effects of a realistic dust field and the resulting impacts on climate.

Assess the impact of increased dust input on marine productivity.

Marine Bio-Productivity: Chlorophyllhttp://earthobservatory.nasa.gov

Dust Effect on Marine EcosystemIron HypothesisEven at high levels of nutrients (e.g. Nitrate, phosphate) certain ocean areas show less bio-productivity, i.e. Phytoplankton growth [Martin et al., 1988]Iron can be a controlling factor for marine live in high-nutrient low chlorophyll (HNLC) regionsIron contained in desert dust blown over ocean regions can contribute to iron supply in such regions, increasing bio-productivity and ultimately Co2 uptake

NASA

Dust Effect on Marine EcosystemWHOI

Marine Ecology: Iron Fertilization ExperimentNatural plankton bloomPlankton bloom after artificial addition of iron (LOHAFEX experiment)

Coral BleachingCoral Bleaching: loss of intracellular endosymbionts due to expulsion or loss of algal population [wikipedia]Related to pathogens transported on dust [Shinn et al., 2000]

http://earthobservatory.nasa.gov, Shinn et albleached branchnormal branch

SummaryDistribution of airborne dust particles depends on atmospheric parameters, such as surface winds, vertical mixing, precipitation, vegetation cover

Dust, however, impacts on climate in various waysDirect radiative forcing by dust leading to surface cooling is its best understood climate effectIndirect dust effects on cloud properties or the marine ecosystem are suspected to be important, but remain unquantified so far.