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Temporal and Spatial Distribution of Asian Dust over North America

Temporal and Spatial Distribution of Asian Dust over North America

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Temporal and Spatial Distribution of Asian Dust over North America

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  1. Temporal and Spatial Distribution of Asian Dust over North America Tony VanCuren California Air Resources Board&Thomas Cahill Delta Group University of California, Davis

  2. Kosa (“Yellow Sand”) in Asia April 1, 1998

  3. Asian Dust in North America April 28, 1998

  4. Why Care About Aerosol Dust? • Condensation Nuclei • Reaction Surfaces • Radiation Effects • Ocean Fertilization • Visibility Impairment • Human Health • Anthropogenic Components

  5. Why Asian Dust? • Dominant over North Pacific • Historical and modern large events • Accompanied by Asian air pollutants • Contributes to downwind “background” • Tracer for hemispheric circulation • May be subject to cycles and trends • Calibration of Pleistocene and modern aerosols for climate modeling

  6. Approach • Define Asian dust chemical signature from known transport events. • Search long term aerosol data bases for chemically similar events. • Control for “overlap” with other dust sources affecting North America (local, Mexico, North Africa, etc.).

  7. NorthAmericanvs. Asian Dust Source Regions

  8. Takla Makan vs U.S. Deserts 200 nm

  9. Takla Makan - Lop Nor

  10. Takla Makan Dust Event

  11. TOMS Aerosol DepthApr 15-May 2 1998

  12. April 29, 1998

  13. Model Confirmation

  14. Western IMPROVE Sites (1998)

  15. A Regional Extreme Event

  16. “SOIL” at 36 IMPROVE SITES 4/15 - 5/6 ‘98

  17. Standardized Si-ratios for 6 Elements7 Days - 33 Sites - 79 Clusters

  18. 2.0 1.5 Normalized Ratio to Silicon 1.0 0.5 0.0 BRID PINN BLIS WHRI CORI BIBE INGA JARB CRLA YELL BRLA CANY BRCA GLAC SNPA DEVA WEMI GRCA LAVO SOLA REDW GRBA GRSA SEQU PORE SCOV YOSE TONT SAGO SALM SAWT CRMO MEVE ROMO 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Chemical Composition Test Set STANDARDIZED COMPOSITION PROFILES 4-29-98 Asian Type 1 Asian Type 2 Fe Al Mg Ca Mn Ti

  19. Dust ClassificationTOP 12 of 640 COMPOSITIONAL CLUSTERSCRATER LAKE, OR

  20. Dust ClimatologyMauna Loa, HI

  21. Dust ClimatologyRedwood N.P., CA

  22. Dust ClimatologyLassen N.P., CA

  23. Eastern Pacific Basin - Monthly Frequency (%) MOUNTRAINIER 436 m

  24. Eastern Pacific Basin - Dust Concentration MOUNTRAINIER

  25. Continental Transect - Monthly Frequency (%)

  26. Continental Transect - Dust Concentration

  27. Atlantic Region - Monthly Frequency (%)

  28. Asian Dust over the Caribbean Sea SEAWifs April 2001NRL Monterey

  29. Frequency at High Altitude

  30. Concentration at High Altitude

  31. Reality Check - Is This Credible? • Was the 1998 event unequivocally Asian? • Is there corroborating evidence for the temporal and spatial structure of the data? • Is there corroborating evidence for the long term consistency? • What new data are on the horizon?

  32. Was the 1998 event unequivocally Asian? • Husar, et al. 2000 • TOMS and SEAWifs imagery show dust clouds • Simultaneity of PM spikes in many data sets • Uno, et al., 1999 • Model dust generation based on wind speed only • Transport using standard CSU-RAMS code • Closes with observational data • Claiborn, et al., 2000 • Dust events at Spokane show elevated urban PM10, small increase in PM2.5, no change PM1 • April 1998 Asian dust events showed elevated PM2.5, PM1

  33. Corroborating evidence for the temporal and spatial structure of the data? • Yienger, et al., 2000 • GCM shows persistent synoptic “pulsating” transport for Asian CO in Western U.S. and Central Canada • Chung & Yoon, 1996 • ROK AF Pilot Reports: “Kosa” commonly observed 600-3000 m AGL • Wang, et al., 2000 • Abundance of fines related to deflation of Loess Plateau • Model calculations show coarse dust near surface w/ fast removal; long-lived fines in elevated layer over E. China, China Sea, and W. Pacific

  34. Corroborating evidence for long term transport consistency? • Canadian Data • Barrie, et al., 1992 POPs & Heavy Metals in NWT • Greenland Data • GRIP - Steffensen, 1997 - Dust size distributions in snow, firn, and ice column show MMD ~2mm with abundant mineral fines • GISP2 - Biscaye, et al., 1997 - 87Sr/ 86Sr, 143Nd/ 144Nd, 206Pb/ 207Pb isotopes show Gobi sand, China loess as source of <5mm dust over last 25,000 years

  35. What new data are on the horizon? • Dust Events 1999, 2000, 2001 • ACE Asia 2001 • Source area monitoring China, Korea, Japan, • Receptor monitoring - Ron Brown (NOAA), Hawaii, Crater Lake. • IMPROVE expanded network • CFCAS - UBC (McKendry) A/C Profiles

  36. Conclusions • Asian transport is persistent except in winter. • Typical tropospheric PM2.5 dust concentrations range from .5 to 1 mg/m3. • MBL strongly limits ground contact at west coastal sites. • CBL limits ground contact below 1000 m except in spring. • Transport layer top is typically near 3000 m. • Tropical transport is limited by seasonal migration of trade wind zone.

  37. Future Work • Calibrate to long term records. • Quantify accompanying anthropogenic gas and aerosol pollutants. • Analyze mineral affinities. • Determine natural and anthropogenic components of the dust.