1. NARSTO PM Assessment NARSTO PM Assessment Chapter 5: Spatial and Temporal Pattern TOC Introduction Data Global Pattern NAM Dust NAM Smoke NAM Haze NAM Total PM Local PM Dust over North America TOCIntroductionDataGlobal PatternNAM DustNAM SmokeNAM Total PM Section Contents Fine Dust Concentration Sahara Dust Plume in July Sahara Events over the Gulf Coast Seasonal and Secular Trends of Sahara Dust over the US Global Scale Dust Transport: The April 1998 Asian Dust Event Asian Dust Impact on NAM: A Spatial and Temporal Perspective Dust Generated within in North America?? Direct questions to Rudolf B. Husar rhusar@me.wustl.edurhusar@me.wustl.edu

2. Sahara Dust Plume in July Based on TOMS Satellite. Work of Herman, Prospero….TOMS In July (1998) elevated levels of absorbing aerosol (Sahara Dust) reaches the Gulf of Mexico and evidently, enters the continent. High TOMS dust levels are seen along the US-Mexican borders, reaching New Mexico. Higher levels also cover the Caribbean Islands and S. Florida. Another patch of absorbing aerosol (local dust?) is seen over the Colorado Plateau, well separated from the Sahara dust.

5. Fine Dust Concentration Based on IMPROVEIMPROVE See Sisler & MalmSisler & Malm The year average Fine Dust is highest over the Gulf region (> 1 ug/m3). In Texas and the West, Fine Dust accounts for 10-25% of the Fine Mass.

6. Fine Particle Dust Concentration Over the East Coast Seasonal Pattern of Dust from IMPROVE Strong peak in July. Dust trace extends to Shenandoah Dust is highly episodic: 90 percentile is >> median Lots of previous work by Prospero, Cahill, Malm …

7. Seasonal and Secular Trends of Sahara Dust over the US Daily dust levels at 6 IMPROVE sites over the SE US were averaged to indicate regional values. Regional Sahara Dust events occur several times each summer (as shown by Prospero, Cahill, Malm….) Seasonal pattern peaks sharply in July when the Sahara plume swings to ne North into the Caribbean. The July average dust declines from 7 ug/m3 in S Florida to about 1 ug/m3 in Shenandoah.

8. Sahara Events over the Eastern US PM10 in Sahara Dust Events The Sahara dust impact on PM10 is not confined to fluke events. In fact, the regional PM10 concentrations over the entire Eastern US (90 th percentile) occur in July over the Gulf Coast Hence, Sahara dust is the dominant contributor to peak PM10 levels over the Gulf Coast (and over the EUS & NW Mexico?). The Sisler & Malm analysis also shows that Fine Dust over the entire US is highest over the ‘Sahara impact region’. Issue: Can this be true????RBH Based on PM10 data in EPA’s AIRS. Previous work by Prospero, Cahill, Malm … Scanning the AIRS PM10 database several regional-scale PM10 episodes over the Gulf Coast (> 80 ug/m3) Three such episodes are shown on the right for July 5, 1992, June 30, 1993 and June 21, 1997. Speciation data (IMPROVE) show that during the events, the fine particle dust exceeds 20 ug/m3.

9. Global Scale Dust Transport: The April 1998 Asian Dust EventThe April 1998 Asian Dust Event Approximate location of the April 19 dust cloud over the Pacific Ocean based on daily SeaWiFS, GMS5/GOES9/GOES10 and TOMS satellite data. Over the Pacific Ocean, the dust cloud followed the path of the springtime East- Asian aerosol plume shown by the optical thickness derived from AVHRR data. a. GOES 10 geostationary satellite image of the dust taken on the evening of April 27. The dust cloud, marked by the brighter reflectance covers the entire northwestern US and adjacent portions of Canada. A dust stream is also seen crossing the Rocky Mountains toward the east. b. Contour map of the PM10 concentration on April 29, 1998. Note the coincidence of high PM10 and satellite reflectance over Washington c. Regional average daily PM10 concentration over the West Coast. The sharp peak on April 27-30 is due to the Asian dust.

10. The Asian Dust Event over NAM: A Spatial and Temporal Perspective The PM2.5 dust concentration data from the IMPROVE speciated aerosol network show virtually no dust on April 25th, high values over the West Coast on April 29 th and dust further inland on May 2. Evidently, on April 25th the dust layer seen by the sun photometers was still elevated since the surface dust concentration was low. The average PM2.5 dust concentration at three IMPROVE monitoring sites over the 1988-98 period was well below 1  g/m 3 On April 29, 1998 the sites show simultaneous sharp rise to 3-11  g/m 3. Evidently, the April 1998 Asian dust event caused 2-3 times higher dust concentrations then any other event during 1988-1998.

11. Size and Composition of the ‘Global’ Dust Volume (mass) size distribution of long range transported ‘global’-scale dust. MMD ~ 2-3 um. Both the aged Sahara and East Asian dusts have fixed composition. East Asian dust is enriched in Fe, CA and K compared to the Sahara dust.

12. Dust Generated within in North America?? Buds, can you spare some of your ideas? This section really needs ideas! There must be dust generated in different parts of North America. But: –Where –When –How much –How do we document it?

13. Summary of Dust Pattern over North America Sahara, Sahara, Sahara Occasional Asian Dust Some ‘local’ NAM dust but –Where –When –How much OK, Are YOU provoked yet?

14. NARSTO PM Assessment NARSTO PM Assessment Chapter 5: Spatial and Temporal Pattern TOC Introduction Data Global Pattern NAM Dust NAM Smoke NAM Haze NAM Total PM Local PM Speciated Seasonal Fine Dust Percentiles over the Eastern US TOCIntroductionDataGlobal PatternNAM DustNAM SmokeNAM Total PM The seasonal aerosol aerosol pattern at the IMPROVE sites is examined using two methodologies: –Seasonal Percentile Frequency Charts

15. Method 2: Seasonal Percentiles, 1992-99 At Lye Brook, VT, the clean days (20 percentile) corresponds to ~4 ug/m3 throughout the year The dirty days are (80-90%-ile) have 2-5 times higher concentration than the clean days. Great Smoky Mtn. Lye Brook Clean days (20%) ‘Clean’ days (20%) Dirty days, 80-90% At the Smoky Mtn, the clean days in the winter are also ~4 ug/m3. However in the summer, even the ‘clean’ days have 14 ug/m3 PM2.5. The dirty days are have 2-3 times higher than the clean days through out the year. The charts depict the magnitude of seasonal and synoptic variation The synoptic-scale variation (day-to-day) can be measured by the 20-80 percentile spread

16. Regional Grouping of Sites For this presentation the IMPROVE sites were grouped as follows: –New England () –Mid-Atlantic () –Central EUS () –Peripheral () For each region, the seasonality is displayed for: –Chemical Mass Balance –Carbonaceous Mass Balance –Fine Particle Mass Percentiles –Coarse Mass Percentiles –Sulfate Percentiles –Fine Soil Percentiles –Tot. Carbon. + 'Unknown' Percentiles –Smoke Organics Percentiles

17. New England: Fine Soil Percentiles Fine Dust Lye Brook Acadia

18. Mid-Atlantic: Fine Soil Percentiles Fine dust Shenandoah Washington DCBrigantine Dolly SodsJefferson

19. Central EUS: Fine Soil Percentiles Fine dust Upper BuffaloMammoth CaveShining Rock G.Smoky Mtn. Sipsy

20. Peripheral Sites: Fine Soil Percentiles Fine Dust Badlands Big Bend VoyageursAcadia Everglades

21. New England: Coarse Mass Percentiles Coarse mass Lye Brook MoosehornAcadia

22. Mid-Atlantic: Coarse Mass Percentiles Coarse mass Shenandoah Washington DCBrigantine Dolly SodsJefferson

23. Central EUS: Coarse Mass Percentiles Coarse mass Upper BuffaloMammoth CaveShining Rock G.Smoky Mtn. Sipsy

24. Peripheral Sites: Coarse Mass Percentiles Badlands Big Bend VoyageursAcadia Everglades Coarse mass