The Asian Dust Event of April 1998

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The Asian Dust Event of April 1998

• A preliminary report prepared by an
• Ad Hoc Virtual Workgroup
• May 11, 1998
• Draft - Please use the Feedback page for comments

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• This preliminary account of the extreme Asian
  dust event of April 1998 is the result of a
  collaboration (sharing of resources) by a virtual
  web-based community that was created
  spontaneously during the dust event. The shared
  workspace of the community was the Dust Event
  website, http//capita.wustl.edu/ASIA-FAREAST/.
• Virtually all of the forty registered and many
  non-registered participants have contributed
  observations, monitoring data, interpretation or
  helped the creation of the virtual community.
  The institutions of the participants included
  state air quality management agencies, government
  laboratories, universities, and private citizens.
• This is an evolving document, subject to changes
  based on the feedback from the community.

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The Dust Storm in Western China and its Transport
Across the Pacific Ocean
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On April 15th, 1998 an unusually intense dust
storm began in the western Chinese Province of
Xinjiang, just in time for the east Asian dust
season. CNN reported that 12 people were missing
from that singular event.
Area Map of Xinjiang Province
CNN Video Clip of Dust Storm
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On April 16th, routine examination by Washington
University of SeaWiFS satellite images first
detected a distinct yellow dust cloud over
central China.
SeaWiFS Image of Dust Cloud over China on April 16
Animation of the Dust Cloud from GMS-5
(Geostationary Satellite on April 19
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On April 19th another dust front moved across
China. By April 20th, the elongated dust cloud
covered a 1000 mile stretch of the east coast of
China. The Chinese Academy of Sciences reported
a yellow rain in Beijing.
SeaWiFS Image of Dust Cloud on April 19
SeaWiFS Image of Elongated Cloud on April 20
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On April 23rd and 24th, the dust storm was
rapidly moving across the Pacific Ocean. The
dust cloud appeared as a yellow dye and
visualized its own path across the Pacific.
Approximate path of the dust cloud as it
transited the Pacific Ocean
SeaWiFS Image of Cloud Approaching North America
on April 24
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During the trans-Pacific transit the dust plume
was also tracked independently by Washington
University and University of Wisconsin using
GMS-5 and GOES-9 geostationary satellites,
respectively.
GMS-5 Image of Dust over the Central Pacific on
April 24
GOES-9 images of Dust over the Central Pacific on
April 24
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Observations of the Asian Dust Event Over the
Pacific Coast of North America
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By April 27th, the dust cloud rolled into North
America. Goes-10 and SeaWiFS images indicate
that the dust plume split once it reached land -
one branch heading southward along the California
coast and another branch continued eastward
across the Canadian Rockies.
GOES-10 Image of Dust Cloud on April 27
SeaWiFS Image of Dust Cloud on April 27
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The normally blue sky was observed to be notably
milky and washed out over much of the West on
April 27th. University of Nevada monitored the
aerosol optical depth prior and during the event.
Milky Appearance of Sky at Sunset in Reno on
April 27
Aerosol Optical Depth Monitoring at Reno Show AOT
in Excess of 0.5 During Dust Event
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By serendipity, the size distribution of the
Asian dust was measured by the University of
Washington aircraft. The State of Washington
Dept. of Ecology conducted routine monitoring of
PM10 and PM2.5 concentrations.
Size distribution data of the dust indicate that
most of the mass is above 2.5umin diameter.
Surface based monitoring of PM10 and PM2.5
indicates that during the dust event 2/3 of the
PM10 mass was above 2.5um
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LIDAR aerosol data by the Jet Propulsion
Laboratory reveals that height of the dust layer
on April 27 at Pasadena, CA was in the range of 6
- 10 km above sea level.
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Air Quality Management Activities
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The Activities of AQ Management Agencies

• Based on public complaints and monitoring data,
  the State of Washington Department of Ecology
  issued a ban on open burning on April 29th.
• On April 29th, the PM alarm went off at several
  continuous monitoring stations around Vancouver,
  BC, because the concentration exceeded 50 ug/m3.
  The British Columbia Ministry of the Environment
  has investigated the underlying causes of the
  particulate matter event.
• California Air Resources Board scientist have
  explored whether the cause of the high PM10
  concentrations (. 50ug/m3) at many sites could be
  attributed to large prescribed burns in Oregon,
  Idaho, and Washington.
• At the South Coast Air Quality Management
  District in Los Angeles, reduced visibility and
  elevated PM10 measurements were initially
  attributed to large scale prescribed burns in
  Idaho and later to the Asian dust.
• United States Department of Agriculture - Forest
  Service in Idaho was concerned about intense haze
  around Salmon and Challis National Forests and
  the possibility of smoke impact from prescribed
  fires. By April 29th, the Idaho Department of
  Environmental Quality has advised that the haze
  may be due to the Asian dust event.

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The Role of the Virtual Community

• Virtually all the Air Quality management agencies
  have participated in creating an instant virtual
  community and have benefited from the information
  resources on the Website in making their quick
  decisions.
• On April 30, the State has issued an explanation
  to the public that now seems fairly certain
  that the Eastern Washington air stagnation event
  is due mostly to Chinese dust rather than locally
  generated pollutants. In the press release, the
  Dust Event Website address was given to the
  public for further information on the event.
• It could be said that the community and its
  shared web resources have contributed certain
  amount of JITERS (Just In Time Environmentally
  Relevant Science) to the AQ managers.
• Evidently, the trust of the managers in the
  available science support arose from the
  multiplicity of independent observations, and
  from weight of the evidence. (Managers, is this
  true?)

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Acknowledgements

• Anderson, T.
• Arimoto, R.
• Bachmeier, s.
• Brock, C.
• Chavez, P.
• Conel, J.
• Dubois, D.
• Durkee, K.
• Falke, S.
• Gasso, S.
• Gill, T.
• Hansen, T.
• Helmlinger, M.
• Hennessey, J.

Holben, B. Huebert, B. Husar, R. Husar,
M. Jackson, G. Jaffe, D. Johnson, B. Juric,
S. Li, F. Lyle, K. Lyons, W. Merrill, J. Miller,
R. Mims, F.
Porter, J. Redmond, K. Reheis, M. Reynolds,
R. Rogers, W. Sakiyama, S. Schichtel, B. Schnell,
R. Tratt, D Van Hook, B. VanArsdale, A. and
many others