timothy logan university of north dakota department of atmospheric science
TRANSCRIPT
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Timothy LoganTimothy Logan
University of North DakotaUniversity of North Dakota
Department of Atmospheric ScienceDepartment of Atmospheric Science
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Outline Aerosol Characteristics
Formation and Behavior Aerosol Detection and Transport
Asian aerosol eventsPast research findings
Aerosol ClassificationCurrent researchSeasonal variability
Research ApplicationsPrimary tools and methodsMain goals and applications
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Aerosol Characteristics
http://www.sciencenews.org/view/feature/id/65734/title/The_final_climate_frontiers NASA Terra Image 20 Mar 2011
Anthropogenic Aerosols Natural Aerosols
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Aerosol Detection Size and composition of aerosols
Attenuation of EM radiation illustrates the nature of aerosols○ Aerosol optical depth (AOD)
Aerosol attenuation (extinction) is the sum of the aerosol scattering and absorption of light○ Extinction part – correlated with size○ Absorption part – correlated with composition
Recent studies looking into thisMain focus of current research
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Aerosol Detection
My past researchUsed dependence of extinction AOD over a
wavelength interval (Angstrom exponent or )○ Distinguishes between small and large aerosols
Fine mode vs. coarse mode aerosols
○ Does not distinguish aerosol compositionSome pollution aerosols can disguise themselves as large size
natural aerosols
Detected Asian aerosol events capable of transporting large amounts of dust and pollution via the Pacific Ocean to North America○ Primarily used aerosol size as a proxy
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Aerosol Transport
AOD > 0.2
AOD > 0.4
AOD > 0.6
Aerosol Transport TrendAerosol Optical Depth
Frequency of Occurrence
Major Aerosol Regions
MODIS AOD Retrievals
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Aerosol Classification
Current research uses second derivative of the absorption part of AOD Spectral curvature or absslope of absDevelop a classification scheme that reduces
ambiguities in Asian aerosol compositionPreliminary results show a clustering of
different types of aerosols○ Sulfate, biomass, mineral dust, black carbon○ Can also see a seasonal variability and rate of
change of Asian aerosol composition
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Desert Regions
Clean Region
Urban Region
2008 AERONET Derived Aerosol Seasonal Variability
Discussion (Absorption)• Most mean abs values for the two seasons fall between 1 and 2 (red lines)
• Mean abs (blue line) explains seasonal variance
• Summer – mean abs is slightly negative
• Sulfate and/or other scattering aerosols
• Winter – mean abs is much higher
• Indicating strong absorption• Result of coal and wood combustion for heat
Xianghe, China 39N 117E
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Research Applications
My research both past and present relies heavily on in situ AERONET, aircraft, space based, and re-analysis observations.NASA sponsored/maintained platforms
Main goal of research is to classify aerosols and the variability of their compositions as they transport far away from their source regions Determine their effects on climate change and
human health
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Thank You
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Extra Slides
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Aerosol Characteristics
Aerosol formationClassified as either man-made (anthropogenic) or
natural
Aerosol behaviorIn terms of climate change – direct vs. indirect effect
○ Influence solar radiation vs. cloud physical propertiesEffects are influenced by physical and chemical
properties of aerosols○ Radiative properties, size and chemical structure
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