Atmospheric Aerosols & Climate

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Published on September 24, 2008

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Atmospheric Aerosols and Climate : October 31, 2001 1 Atmospheric Aerosols and Climate Crew Familiarization Talk Chapter 2 Joachim H. Joseph Aerosols?! Aerosols...????Aerosols…!!! : Aerosols?! Aerosols...????Aerosols…!!! Contents of this Chapter : October 31, 2001 A - 3 Contents of this Chapter Outline the nature of aerosols Introduce the study of aerosols Describe their Importance in Atmospheric Phenomena on all Time and Space Scales with particular emphasis on Climate and Remote Sensing The Desert Aerosol Why study aerosols? : October 31, 2001 A - 4 Why study aerosols? Reduce/Increase GHG’s Warming, Affect Cloud and Rain, Interfere with Remote Sensing of EAS, Active in Atmospheric Chemistry, Supply Minerals to Ocean Biosphere, Affect Well- Being of Organisms on both Land and Sea: Contain Spores, Microbes and Viruses, Acids and other stuff. Aerosol Involvement in the EAS.“EAS”= Earth Atmosphere System : October 31, 2001 A - 5 Aerosol Involvement in the EAS.“EAS”= Earth Atmosphere System Spatial Scales: Local/ Regional/Global Natural and Man- Made Air Pollution Radiation Balance Clouds, Precipitation and Hydrology Health Hazards Time Scales: Diurnal/Synoptic/Seasonal/ Decadal, Climatic : Industrial plumes, Haboobs, Biomass Burning, Khamsins, Dust Plumes, Continental Pollution “Mountains”, Volcanic Eruptions. Slide 6: October 31, 2001 6 The Earth- Atmosphere Thermodynamic System. Slide 7: October 31, 2001 A - 7 Radiative Effects of Aerosols in Solar Spectrum. Proving need for Space- based Observations. When does aerosol heat/cool? : October 31, 2001 A - 8 When does aerosol heat/cool? From the previous slide we have: The sign depends on d, w0 and g, through t and r BUT IN ADDITION ON A, THE LOCAL SURFACE ALBEDO! THE SAME AEROSOL MAY HEAT OR COOL DEPENDING ON THE SURFACE OVER WHICH IT IS LOCATED!!! The Study of Aerosols from Space. : October 31, 2001 A - 9 The Study of Aerosols from Space. The regional and global spatial distribution of any aerosol determines its climatic effect. The combined climatic effect of all atmospheric aerosols together depends on their combined spatial distribution Therefore the study of aerosols from space is MANDATORY!!! Aerosols versus GHG’s : October 31, 2001 A - 10 Aerosols versus GHG’s Aerosols are wide- spread, localized, transitory and highly variable on all space and time scales Atmospheric GHG’s are globally distributed in a vastly more homogeneous manner and vary in time mostly on seasonal and longer time scales. What is an Atmospheric Aerosol? : October 31, 2001 A - 11 What is an Atmospheric Aerosol? Mixture of Particles and Gases with Suitable Degree of Definability over Time Span of Relevance to the Observed System Elaboration on Definition- 1 : October 31, 2001 A - 12 Elaboration on Definition- 1 “Particles” Liquid: Drops of Solutions Solid: Single Chunks/ Aggregates /Flakes Solid/ Liquid Drops with Solid Inclusions Liquid Coated Aggregates “Gases” Any mixture of gases Particle Mixture- External or Internal Elaboration on Definition- 2 : October 31, 2001 A - 13 Elaboration on Definition- 2 “Suitable Degree of Definability over Time Span of Relevance to the Observed System” Having a set of measurable physical and chemical properties that define its interactions with the ambient atmosphere; These properties change slowly compared to the time constant of interaction of the aerosol with other components of or processes in the observed system. Examples of Aerosols : October 31, 2001 A - 14 Examples of Aerosols The Atmosphere: More exactly, it is a system of many different aerosols existing simultaneously; Wind- Blown Mineral or Soil Dust Natural/Industrial Hazes/Fogs/Smogs/Smokes Water/Ice Clouds Atmospheric Aerosols:A Practical Definition : October 31, 2001 A - 15 Atmospheric Aerosols:A Practical Definition The ensemble of all liquid/solid systems suspended in the atmosphere, except water/ ice clouds. Water and Ice clouds are conventionally excluded because of their tight involvement with the hydrological cycle, short lifetimes and involvement in long- range latent energy transport. Main Types of Aerosols : October 31, 2001 A - 16 Main Types of Aerosols Continental/ Desert Aerosols Marine Aerosols Industrial Aerosols Volcanic Aerosols Organic Forest Hazes Smoke/Biomass Burning Aerosols Stratospheric Aerosols Each “Type” has several “Components” : October 31, 2001 A - 17 Each “Type” has several “Components” Wind- Blown Mineral Dust Sea Spray Natural or Man- Made gas to particle conversion products- e.g. volcanic/ industrial emissions, DMS Natural Hazes from organic volatiles- e.g. terpenes , isoprenes Natural /Industrial direct emissions- e.g. soot, ash, smoke, biomass burning Average Residence Time of Aerosols in Atmosphere : October 31, 2001 A - 18 Average Residence Time of Aerosols in Atmosphere Present Main Foci of Research: : October 31, 2001 A - 19 Present Main Foci of Research: Aerosol Processes: Sources, Sinks, Transport, Components of Types, Relation of Size/Shape/Composition, Time Constants, … Direct /Indirect Radiative Forcing of EAS Effects on Remote Sensing of EAS Biosphere/ Atmosphere Interactions e.g. NMHC, VAT, Fires and Biomass Burning Aerosols Oxidants and Photochemistry:e.g. tropospheric ozone and its precursors, Radicals Health Hazards International Research Efforts : October 31, 2001 A - 20 International Research Efforts Some Recent Comprehensive Campaigns. ACE1- US Air Pollution, ACE2- European Air Pollution & Desert Aerosol, ACE3- “ACE-ASIA”) East Asian Aerosols, and Desert Aerosols. TARFOX- US Air Pollution, SCAR- A,- Eastern Seaboard Air Pollution, SCAR- B- Biomass Burning in Brazil , SCAR-C- CA Air Pollution SAFARI 2000, etc. … Satellite Programs: SAGE, EOS, ADEOS, SEAWIFS, Pegasus, … Robotic Surface Photometer Network: AERONET AMIP- Climate Model Comparisons Slide 21: October 31, 2001 A - 21 The 2D distribution of the average value of positive TOMS AI for each pixel for the period from August, 1996 to April, 2000 (top panel). Main source regions of the UV-absorbing aerosols can be inferred, and these regions are marked in the bottom panel. The North African Desert Aerosol Sources. (Alperovich, Joseph, Levin and Ganor, JGR 2001) Slide 22: October 31, 2001 A - 22 Top panel: The distribution of the highest observed TOMS AI. The largest values occur along the main trajectories of the dust plumes. Bottom panel:Schematic of the main routes of the desert aerosol transport. Desert Aerosol Transport over North Africa and the Mediterranean. (Alperovich, Joseph, Levin and Ganor, JGR 2001) The Desert AerosolGlobal Phenomenon with Regional Implications. : October 31, 2001 23 The Desert AerosolGlobal Phenomenon with Regional Implications. Sub- Tropical Sources: Sahara and its Boundary Regions, ME, Saudi, Indian Deserts; South- African and Australian Deserts Middle & High Latitude Sources: Mongolia, Siberia, Gobi, Afghanistan Slide 24: October 31, 2001 A - 24 Chemical and mineralogical analysis of individual mineral dust particles A.Falkovich, E. Ganor, Z. Levin, P. Formenti and Y. Rudich, JGR, 2000 (in press MINERAL DUST PASSING OVER LAND. Mark! Highly Non- Spherical Shapes! Why are DA’s, in contrast to others, so irregularly shaped? : October 31, 2001 A - 25 Why are DA’s, in contrast to others, so irregularly shaped? Rain on Mountain Massifs; Run- off of silt into wadis and playas; Formation of playa soil- hollow spherules with a range of radii from tens to hundreds of microns, weakly cemented by water or other materials; Dry Out of soil; Turbulent weather systems mobilize particles; Saltation leads to break- up of spherules; The broken air- borne fragments: Desert Aerosol. ANALYSIS OF THE SLOPE - FRACTAL DIMENSION- OF THE LOG PERIMETER VS. LOG AREA GRAPH AT 08:00 AM.(Koren and Joseph, JGR 2001) : October 31, 2001 A - 26 ANALYSIS OF THE SLOPE - FRACTAL DIMENSION- OF THE LOG PERIMETER VS. LOG AREA GRAPH AT 08:00 AM.(Koren and Joseph, JGR 2001) Simple Shapes Complex Shapes Fractal Dimension Fractal Dimension (Calculated Diameter, mm) Fractal Dimension ( Area in Pixels) A Multi- Resolution Look at the Desert Aerosol : October 31, 2001 A - 27 A Multi- Resolution Look at the Desert Aerosol Summary of Problems : October 31, 2001 A - 28 Summary of Problems The effects of aerosols are difficult to assess Aerosols are a very very minor component of the atmosphere and very difficult to measure Aerosols are very varied and complex in nature at any time and location Aerosols are highly inhomogeneously distributed and highly episodic in occurrence Aerosols need to be studied interdisciplinarily Aerosols need to be studied simultaneously from space, air and ground and in the lab. Slide 29: October 31, 2001 A - 29 END

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