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Update:  A second Asian haze event began late in the day on Sunday, April 22nd, persisted on April 23rd before clearing out on Tuesday, April 24.  NOAA Research, Boulder, Colorado confirmed this second event in an April 24th Press Release.
This second haze layer was confined in a layer 7-9 km aloft.  It did not mix down to the ground like the April 12th event.

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Second Documented Asian Haze Event - Page, Arizona - April 23rd.


The Easter Weekend 2001 - Great Basin Event  

Impact on Northern Arizona and Southern Utah

"So thick was the dust over Easter weekend that visitors to western U.S. national parks have reportedly been asking rangers where the "fire" is.  Normally only smoke from major fires causes such haze."  
                                                                                                                           Discovery Channel Earth Alert

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Figure Caption: The Mongolian desert dust cloud which passed over Boulder, Colorado during the April 13-18 period apparently also contained carbon monoxide, possibly entrained as the cloud passed over industrial regions between Asia and the U.S. The figure shows the vertical profile of the dust particles, as obtained by laser radar (lidar) at Boulder, and of the profile of carbon monoxide, as obtained with an automated aircraft flask air sampler. The two measurements were not made simultaneously but about 36 hours apart (April 15 - pm, April 17 - am). However, both visual and photometer measurements from the surface at Boulder indicated that the cloud persisted throughout this period with optical depths of 0.3 to 0.4 at 500 nm wavelength.  (Figure and caption - NOAA Climate Monitoring & Diagnostics Laboratory)


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Asian Dust Cloud Over Page, Arizona - April 14, 2001 - Two days after first arrival


Haze at Bryce Canyon on April 14, 2001
Photo by Dave Tarkington

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                              Grand Canyon Without Haze                                                  April 15, 2001
                                   Photo by Alan Piper                                                        Photo by Alan Piper


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  Page, Arizona Looking East Toward Navajo Mountain                                              April 16, 2001                             

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         Glen Canyon National Recreational Area                                                         April 16, 2001
         Looking toward the Kaiparowits Plateau

The April 13 - 15, 2001 Great Basin Event

Update:  This event has been officially confirmed by:
Jay R. Herman, Principal Investigator for TOMS Aerosol/UV projects, NASA/Goddard Space Flight Center
Douglas L. Westphal, Naval Research Laboratory in Monterey, California
Gene Feldman, NASA/Goddard Space Flight Center
Russ Schnell, Director of Observatory Operations, NOAA, Boulder, Co.

The front edge of a huge Asian dust cloud reached Page, Arizona at 5 p.m.on Thursday, April 12th with a dramatic and very distinct frontal boundary.  Within hours, a thick veil of dust covered the entire sky.

The haze layer was initially confined to layers aloft (April 12 and 13th) but by April 14th and 15th as subsidence set in with a developing high pressure system, the main band of aerosol moved down to lower levels and the local visibility which is normally unlimited (over 100 miles) was reduced down to 30 miles or less.  The trapped hazed layer persisted in Page, Arizona until the April 16th.

The Asian Cloud at higher levels was eventually tracked into the Midwest region of the United States.  On Wednesday, April 18th, Tucson reported an east wind (backdoor transport event) that accompanied a pronounced haze event that briefly lowered visibility to less than 10 miles.  This air mass had a long history and was obviously subject to numerous pollution sources along the way (the Midwest, El Paso, Mexican agricultural burning) but could it have also contained a small remaining percentage of Asian haze?  If so, it would have represented the last hurrah and the official end of the impact of the Asian Dust Cloud to Arizona.

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Field Observations

A Bishop’s Ring around the Sun was very prominent from Flagstaff over the weekend once the dust event started.  Bishop's Rings are typically associated with volcanic ash clouds.  - Brian Skiff, Lowell Observatory

Now in its fifth day, slowly clearing in western NV, very high concentrations, fairly large particles. Really poor visibility in much of the West, even at our mountaintop lab at Steamboat Springs CO, where they noted 40 micrograms/m^3. Sunlight reduction about 1-3 percent. Leading edge nucleated precip in the upper Midwest over the weekend, passed over CPC a day or two ago and is now well on its way to visit Paris. Must have been a really enormous mass overall; seems to considerably exceed the 1998 episode. -  Kelly Redmond, Desert Research Institute, Reno, Nevada

The huge Chinese dust storms that started early in April have continued, essentially unabated. Meanwhile the dust generated from these early storms has crossed the Pacific and has caused widespread haze in the western states. I will start off my coverage by reviewing the dust activity that occurred in China over the past week. Then I will focus on the observations of dust in the western US. My last report was on 11 April. In this report I will present in-depth coverage because I feel that these series of dust storms will be studied for years to come.  - Joe Prospero,

On April 12th, Norman Kuring (NASA Goddard: sent a link to a high resolution Seawifs image showing a heavy band of dust off the west coast of the US.

On 15 April Ken Sassen ("" <>) reports: Subject: Dust over Salt Lake City, Utah.  We have had hazy skys for the past three days, with reduced visibility today.  At 2000 UTC today (15 April) my lidars detected aerosols from ~2.0 to 6.3 km MSL.  The strongest backscattering region from 4.2 to 4.7 km MSL produced strong depolarization at 0.532 micron, indicating relatively large nonspherical particles.

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Salt Lake City LIDAR


On April 17th, Norman Kuring <> sends two high resolution Seawifs image links for the 15th and 16th of April; these show dust off the west coast of the US. Concentrations are lower than on the 12th and 13th but they are significant.

I was out in Death Valley and along the east side of the Sierra Nevada over the weekend and everyone was puzzled by an extraordinary haze that lasted through yesterday. The visibility in Death Valley, normally limitless, was down to ten miles or less. Some folks -- including the National Park Service rangers -- thought it was from fires somewhere, except there were no large  fires burning. I'm curious whether it was the dust from China. That last picture you sent of the dust behind the cloud front off the Pacific coast is compelling. - Larry O'Hanlon


News Articles

Could Dust Storm Be China's Revenge?
        PAGE, Arizona - A yellow haze that has hung over northern Arizona and southern Utah for nearly a week wasn't
        caused by the usual suspects.  Not smoke from a forest fire, not dust from high local winds. The culprit -- a likely
        one of late for other scenarios -- is China, according to the National Weather Service.  A monstrous dust storm in
        the Gobi Desert 12 days ago is responsible for the yellowish sky, low visibility and, for Page residents, Sunday's
        disappearance of Navajo Mountain from view.
          Tues  Apr 17 15:00 EST Arizona Daily Sun - Flagstaff AZ - Mongolian storm pollutes North America - April 18, 2001
HONG KONG, China - A dust storm from Mongolia has dispersed dust from the Gobi Desert and industrial pollution from China across a quarter of the mainland United States and Canada, according to atmospheric scientists. The whitish haze has been seen from Calgary, Canada in the north, to Arizona in the south and as far east as the ski-fields of Aspen, Colorado, The weekend levels...
Wed Apr 18 01:01 EST Turner Broadcasting - Atlanta GA
Dust from China mingles with Chinese pollution across West
Dust from China mingles with Chinese pollution...
Wed Apr 18 04:04 EST Lake Tahoe News Network - Carson City NV
Asian Storm Dusted State
Talk about a big dust storm. One blew in last week from - get this - the Gobi Desert in Mongolia. The whitish haze traveled about 7,000 miles to get here and was detected in northern Arizona by an eagle-eyed meteorologist.
Wed Apr 18 04:46 EST Phoenix Newspapers, Inc - Phoenix AZ
Gobi dust coats West with haze
A haze obstructs the usually clear views of the La Plata Mountains on Monday near Durango. Scientists and the National Weather Service say the haze is the result of a massive dust storm over China s Gobi Desert earlier this month as well as pollution from the Asian continent. The brown cloud is affecting the entire western United States from the Canadian border to Arizona. By Tom...
Wed Apr 18 09:46 EST Durango Herald - Durango CO
CBS News | Mongolian Haze Floats To U.S. | Wed, 18 Apr 2001 13:20:08 EDT
"We know that it is having a visible impact across much of the state." Chris Dan Colorado Department of Health and Environment Mongolian Haze Floats To U.S. Huge Dust Storm Has Long Reach April 18, 2001 AP An April 10 satellite image of the dust cloud. (AP) A dust storm from Mongolia is dispersing dust from the Gobi Desert and industrial pollution from China across a quarter of...
Wed Apr 18 11:41 EST CBS News - New York NY
A storm that kicked dust up into the jet stream in Mongolia sends a mustard-colored cloud across mainland Asia, left, and over the Sea of Japan on April 10. SALT LAKE CITY (AP) — The haze across much of Utah the last few days is a dust cloud that originated 12 days ago in the Gobi Desert of Mongolia and China. Upper-level winds blowing across the Pacific brought the large cloud...
Wed Apr 18 16:06 EST USA Today - Arlington
The Weather Channel - Top Stories Index
The dust storm stirred up accidents involving eleven cars on Oregon's Highway 97. "I knew it was something big - a forest fire, a volcanic eruption, something," said Paul Ostapuk, a meteorologist with the Salt River Project in Utah. "We're so clean and pristine up here, so it's immediately noticeable." Ostapuk was referring to the huge, mustard-colored dust cloud that moved eastward...   Note: The car pileup stories were inaccurately linked to the Asian Haze
Wed Apr 18 20:17 EST The Weather Channel - Atlanta GA
A dust storm that began two weeks ago on the Mongolian-China border reached the U.S. this week, blanketing areas from Canada to Arizona with a layer of dust. In Denver and along the foothills of the Rockies, the mountains were obscured by the haze.
          Wed Apr 18 - National Oceanic and Atmospheric Administration
Official NASA Goddard Space Flight Center Statement
        Despite experts predictions that the Asian dust storms that originated two weeks ago in Mongolia would not make 
         it to the Eastern United States, satellite photos from the SeaWiFS confirms that the dust storms indeed did hit the Eastern
         U.S. by storm. 
Fri  Apr 20  NASA Goddard Space Flight Center

Massive dust cloud to travel over N.E.
    A massive dust cloud containing minute pieces of rock, dinosaur fossils and even mummified human remains will be floating
     over New England today.
     Fri Apr 20  The Boston Globe

Second Asian Dust Storm Over U.S.
        April 24, 2001 — A small Asian dust storm, with about one-fifth the haze effect of the previous storm, is passing over
        Colorado Tuesday. The storm came from the same region of the China-Mongolia area as the previous storm, which
        blanketed Colorado from April 14 to 18.
  Apr 24  NOAA Research, Boulder, Colorado

My, How Dust Travels
        When Mongolian Winds Whipped Through the Gobi Desert, Arizona Got Dusty.  Paul Ostapuk thought a band of dark
         air extending across the western horizon looked a bit odd as his plane descended into Page, Ariz., but he had no way of
         knowing then just how odd it would turn out to be.
        Thu Apr 26

Information Sources

Today's Aerosol Conditions from Earth Probe TOMS*

The Perfect Asian Storm

          Climate Monitoring & Diagnostics Laboratory
Golden Gate Weather Service's April 2001 Asian Dust Cloud page

ACE-Asia (Asian-Pacific Regional Aerosol Characterization Experiment)

SeaWifs Images

Field Notes - Chinese Dust Impacts Western US! - April 2001 Event


The Asian Dust Events of April 1998

JPL ground-based backscatter lidar measurements during the April 1998 event

Sven Hedin’s Account Of the Takla-makan desert, 1895

          Long range transport of mineral dust in the global atmosphere - Joe Prospero


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