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 GHGs 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 Earth- Atmosphere Thermodynamic System.
7
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 GHGs

• Aerosols are wide- spread, localized, transitory
  and highly variable on all space and time scales
• Atmospheric GHGs 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 AerosolsA 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 Photochemistrye.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 panelSchematic 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 DAs, 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
ANALYSIS OF THE SLOPE - FRACTAL DIMENSION- OF
THE LOG PERIMETER VS. LOG AREA GRAPH AT 0800
AM.(Koren and Joseph, JGR 2001)
Fractal Dimension (Calculated Diameter, mm)
Fractal Dimension ( Area in Pixels)
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