NARSTO PM Assessment Chapter 5: Spatial and Temporal Pattern Introduction and Approach

1. NARSTO PM AssessmentChapter 5: Spatial and Temporal PatternIntroduction and Approach Section Contents Chapter Goal and Objectives Policy Issues on PM Aerosol Types: ‘Dust’, ‘Smoke’ and ‘Haze’ General Features of North America Atmospheric Residence Time and Transport Distance Spatial-Temporal Pattern Chapter Structure Direct questions to Rudolf B. Husar rhusar@me.wustl.edu

2. Chapter Goal • Organize the PM Assessment to address the policy issues on PM management. • Present new knowledge that will facilitate making better AQ management decisions. • State how can science be applied to reducing PM concentrations. • Show the linkages among AQ issues: the multi-pollutant atmosphere. • Need a statement on specific objectives for the Spatial-Temporal Pattern Chapter?

3. Policy Issues on PM The specific Policy Issues (stated in the NAS Science-Policy Balance document) • Where/when are the significant PMx (PM10, PM2.5, PM1) problems, and how confident are we • What are the sources of PM that cause the problem • What are the broad approaches to fix the problem? (what pollutants; local/regional; continuous intermittent?) • What specific options do we have for fixing the problem? • What are the relationships between the PMx and other pollutant problems? • How can we measure progress? • When and how should we reassess and update our control program? • What atmospheric science info is needed for the review of NAQS?

4. Aerosol Types: ‘Dust’, ‘Smoke’ and ‘Haze’ • Aerosol are composed of multiple types. Each type may be considered a different pollutant since it has its own class of sources, aerosol properties and associated with different effects. • In other words, dust, smoke and haze have no more commonalities then CO, NOx and SO2 but the happen to be lumped by the current regulations. • For this reason, the chapter will discuss the pattern of aerosol components (types) first and then the total aerosol pattern. • The aerosol population is grouped into three types: DUST = SOIL SMOKE = ORGANICS + SOOT HAZE = SULFATE + NITRATE FMASS = DUST + SMOKE + HAZE • These aerosol types correspond to the IMPROVE aerosol types but further aggregated for reducing complexity: The IMPROVE teps are: SULFATE = 4.125*S Ammonium sulfate NITRATE = 1.29*NO3 Ammonium nitrate ORGANICS = 1.4(O1+O2+O3+O4+OP) 1.4* various organics (OMC) SOOT = E1+E2+E3+OP Light absorbing carbon (LAC) SOIL = 2.2AL++2.49SI+1.63CA+2.42FE+1.94TI Crustal elements FMASS = SULFATE + NITRATE + LAC + OCM + SOIL Reconstructed fine mass CMASS = MT-MF Coarse=PM10-FMASS Issue: The level of aggregation needs discussion. Clearly, no matter how you aggregate it, each type has many variants in nature. I think that the IMPROVE typing (aggregation) used by Malm & Co is good and it should be retained for presenting the network results. However, I also think that DUST, SMOKE HAZE aggregation is beneficial for presenting the general aerosol pattern. I am open for discussion RBH.

5. Aerosol Size & Chemical Composition • Issue: This Figure does not belong in the Spatial Temporal Pattern (STP) chapter of the NARSTO PM doc but I am offering it for consideration by the other authors. • The figure was generated by an international group as part of the IGAC Integration and Synthesis workgroup. • The process of figure creation can be found the here.

6. General Features of North America • Issue: Somewhere in NARSTO PM we could use some general description of the continental features. Examples are here. I will be happy to help if needed. If not we can skip these. RBH

7. Atmospheric Residence Time and Transport Distance • Jaenicke plot: Ultrafine 0.1 m coagulate while coarse particles above 10 m settle out more rapidly. • PM in the 0.1-1.0 m size range has the longest residence time because they neither settle, nor coagulate. • Froelich schem.: PM2.5 residence time increases with height. • Within the atmospheric boundary layer (the lowest 1-2 km), the residence time is 3-5 days. • If aerosols are lifted to 1-10 km in the troposphere,(e.g. by deep convection at fronts or convergence zones) they are transported for weeks and many thousand miles before removal. • Atmospheric residence time and transport distance are related by the average wind speed, say 5 m/s. • Residence time of several days yields ‘long range transport’ and more uniform spatial pattern. • On the average, PM2.5 particles are transported 1000 or more km from the source of their precursor gases. • The residence time determines the range of transport. For example, given a residence time of 4 days (~100 hrs) and a mean transport speed of 10 mph, the transport distance is about 1000 miles. • The range of transport determines the ‘region of influence’ of specific sources.

8. Aerosol Pattern at Different Spatial and Temporal Scales • The spatial and temporal distribution of aerosols can be described by the pattern at different scales • The pattern of ambient concentration is determined by the pattern of their causal factors: emissions, transport and chemistry. • The spatio-temporal pattern of emissions, transport and chemistry may be different at each scale. • Temporal and spatial pattern analysis of PM data is particularly useful for source identification and characterization.

9. Spatial-Temporal Pattern Chapter Structure • The main chapter grouping is by geographic scale: • Global • Continental/Regional • Subregional/Local • Within each section, the pattern are described for: • Dust • Smoke • Haze • Total (PM10, PM2.5, Bext, AOT) Issue: Once we all make our respective contributions and see the chapter contents, it may be good to revisit the the structure for possible revisions. RHB