Atmospheric Aerosols R.B. Husar, Washinton University HTAP Meeting, June 10, 2008, Washington DC
Dimensions of Gaseous Pollutants: X, Y, Z, T Dimensions of Aerosols: Particle Size, Composition, Shape
Bad News: Aerosol Characterization is Challenging
PM is characterized by many sensors, sampling methods and tools
Each sensor covers only a fraction of the 6-Dim PM data space .
The 6 D data space is extrapolated from sparse measured data
Or deconvoluted from integral measurements
For integral sensors, the integral samples need to be separated into components
Once the aerosol is characterized, opportunities exists for extracting information about the aerosol sources, transformations, etc from the data directly.
Phase II HTAP Goal: Integration of Emissions, Models and Observations
Aerosols are Indicators of Many Earth System Processes Including Human-induced Perturbations Volcanoes Dust storms Fires Anthropogenic Pollution EPA NAAQS PM2.5, O3 Exceptional Event Rule Exclusion of data when it is strongly influenced by “exceptional events" (EE), such as smoke from wildfires or windblown dust or LRTP.
The number of satellite-fire pixels Jul-Aug (1997-99)
The daily fire counts shows significant day to day fluctuation
Central American Smoke Plume Surface PM2.5 Ozone
Kansas Agricultural Smoke, April 12, 2003 Fire Pixels Organics 35 ug/m3 max Ag Fires SeaWiFS, Refl Smoke Emission April 11: 87 T/day April 10: 1240 T/d Assuming Mass Extinction Efficiency: 5 m 2 /g
Emission: Red Modeling: Yellow Observations: Yellow
Supporting Evidence: Transport Analysis Satellite data (e.g. SeaWiFS) show Sahara Dust reaching Gulf of Mexico and entering the continent. The air masses arrive to Big Bend, TX form the east (July) and from the west (April)
Sahara PM Events over the Eastern US PM10 July 5, 1992 PM10 June 21, 1997 PM10 June 30 1993 Sahara Dust Sahara Dust TOMS, July Aerosol Index
Asian Dust Cloud over N. America On April 27, the dust cloud arrived in North America. Regional average PM10 concentrations increased to 65 g/m 3 In Washington State, PM10 concentrations exceeded 100 g/m 3 Asian Dust 100 g/m 3 Hourly PM10
~50% of the variability in springtime PM 2.5 in the Western U.S. can be explained by changes in Asian dust (Fischer et al., 2008)