Atmospheric Aerosols and Climate

1. Atmospheric Aerosols and Climate Crew Familiarization Talk Chapter 2 Joachim H. Joseph

2. Aerosols?! Aerosols...????Aerosols…!!!

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

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.

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.

6. The Exhaust: Thermal IR The Fuel: Solar Radiation Greenhouse Gases CLOUDS Aerosols Radiation Transfer- The Atmospheric Carburettor The Atmospheric Heat Engine The Earth- Atmosphere Thermodynamic System.

7. At2 Art2 F0 A2rt t At Art A2r2t A Radiative Effects of Aerosols in Solar Spectrum. Proving need for Space- based Observations.

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!!!

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!!!

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.

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

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

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.

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

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.

16. Main Types of Aerosols • Continental/ Desert Aerosols • Marine Aerosols • Industrial Aerosols • Volcanic Aerosols • Organic Forest Hazes • Smoke/Biomass Burning Aerosols • Stratospheric Aerosols

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

18. Average Residence Time of Aerosols in Atmosphere

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

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

21. The North African Desert Aerosol Sources. (Alperovich, Joseph, Levin and Ganor, JGR 2001) 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.

22. Desert Aerosol Transport over North Africa and the Mediterranean. 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. (Alperovich, Joseph, Levin and Ganor, JGR 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

24. MINERAL DUST PASSING OVER LAND. Chemical and mineralogical analysis of individual mineral dust particles A.Falkovich, E. Ganor, Z. Levin, P. Formenti and Y. Rudich, JGR, 2000 (in press Mark! Highly Non- Spherical Shapes!

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.

26. Average particle diameter in mm Sample No. ANALYSIS OF THE SLOPE - FRACTAL DIMENSION- OF THE LOG PERIMETER VS. LOG AREA GRAPH AT 08:00 AM.(Koren and Joseph, JGR 2001) Fractal Dimension ( Area in Pixels) Fractal Dimension (Calculated Diameter, mm) Simple Shapes Fractal Dimension Complex Shapes

27. A Multi- Resolution Look at the Desert Aerosol

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.

29. END