atmospheric aerosols and climate
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Atmospheric Aerosols and Climate. Crew Familiarization Talk Chapter 2 Joachim H. Joseph. Ae ro so ls ?! A e ro sols... ???? Ae ros ols … !!!. Contents of this Chapter. Outline the nature of aerosols Introduce the study of aerosols - PowerPoint PPT PresentationTRANSCRIPT
October 31, 2001 1
Atmospheric Aerosols and Climate
Crew Familiarization Talk Chapter 2Joachim H. Joseph
Aerosols?! Aerosols...????
Aerosols…!!!
October 31, 2001 A - 3
Contents of this Chapter
Outline the nature of aerosolsIntroduce the study of aerosolsDescribe their Importance in
Atmospheric Phenomena on all Time and Space Scales with particular emphasis on Climate and Remote Sensing
The Desert Aerosol
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.
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.
October 31, 2001 6
The Earth- Atmosphere Thermodynamic System.
October 31, 2001 A - 7
F0
A
t At
Art
A2rt
A2r2t
At2Art2
rA
AtrAFFF
FAF
FrA
AtrF
Twomeyabsorptionofel
seriesgeometricStreamTwoSimple
noneaaerosolaa
aerosolowabsorbed
aerosolinabsorbed
1
1
11
1977mod
2
,,
0..
0
2
Radiative Effects of Aerosols in Solar Spectrum.Proving need for Space- based Observations.
October 31, 2001 A - 8
When does aerosol heat/cool?
Fa Fa,aerosol Fa,none A r t 2A
1 rA
0 : Heats
0 :Cools
From the previous slide we have:
The sign depends on 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!!!
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!!!
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.
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
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
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.
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 DustNatural/Industrial Hazes/Fogs/Smogs/SmokesWater/Ice Clouds
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.
October 31, 2001 A - 16
Main Types of Aerosols
Continental/ Desert AerosolsMarine AerosolsIndustrial AerosolsVolcanic AerosolsOrganic Forest HazesSmoke/Biomass Burning AerosolsStratospheric Aerosols
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
October 31, 2001 A - 18
Average Residence Time of Aerosols in Atmosphere
10
100
1000
104
105
106
107
108
0.0001 0.001 0.01 0.1 1 10 100 1000
Jaenicke, 1980A
vera
ge
Re
sid
ence
Tim
e,
seco
nd
s
Radius, micrometer
Below 1.5 km
MiddleTroposphere
Tropopause
1 Day
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
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 PollutionSAFARI 2000, etc. …
Satellite Programs: SAGE, EOS, ADEOS, SEAWIFS, Pegasus, …Robotic Surface Photometer Network: AERONET
AMIP- Climate Model Comparisons
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)
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)
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
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- SphericalShapes!
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.
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)
Average particle diameter in mSample No.
SimpleShapes
ComplexShapes
Fractal D
imension
Fractal Dimension (Calculated Diameter, m)Fractal Dimension ( Area in Pixels)
October 31, 2001 A - 27
A Multi- Resolution Look at the Desert Aerosol
QuickTime™ and aSorenson Video decompressorare needed to see this picture.
October 31, 2001 A - 28
Summary of Problems
The effects of aerosols are difficult to assessAerosols are a very very minor component of the
atmosphere and very difficult to measureAerosols are very varied and complex in nature at any
time and locationAerosols 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.
October 31, 2001 A - 29