Update on Assessment of the Major Causes of Dust-Resultant Haze in the

WRAP

Vic Etyemezian, Jin Xu, Dave Dubois, and Mark Green

Update• Categorized the events based on the spatial scale of the

events (hazagon maps, spatial analysis) - Transcontinental events, Regional events, Local events

• Identified aerosol signatures of the transcontinental dust. Identified days/sites that are possibly influenced by Asian/African dust based on aerosol signatures, satellite images, NRL modeling results, back trajectories, etc.

• Collected surface meteorology data and built database. • Linking each IMPROVE site with one or more weather

stations• Studying relationship between meteorology data (WS,

WD) and dust concentrations in all 20% worst dust days

Asian Dust Event Arizona Regional Dust Event

Dust Emission/Wind Correlations

• Correlate surface wind measurements with IMPROVE dust concentrations

• Look for relationships between high wind days and high fugitive dust across the IMPROVE network in the WRAP region

• Questions to answer:– Can we extract wind speed thresholds for high wind

events in the IMPROVE data set?– What wind metric is appropriate to flush out these

events?– How can this help to distinguish high dust events that

are local, regional, or large scale?

Dust Emission/Wind Correlations

• Choose wind measurements from nearby representative weather station(s) and rank them

• What is representative? Take in consideration:– Intervening terrain– Nearby geographic features– Distance– Elevation differences between site and met station

Dust Emission/Wind Correlations

• Found reliable multiyear source of surface hourly meteorology for all of US

• Based on Integrated Surface Hourly (ISH) database from the National Climatic Data Center

• Built database of airport surface meteorology from 1999-2002 that we can query and develop a tool to do the comparison

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SAAN1

PEFO1

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GUMO1

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Salt CreekWilderness

Yellow dots are ISH met sitesRed dots are IMPROVE sites

Salt Creek Example4/8/00-12/31/02 IMPROVE dataUsing Roswell AirportASOS winds

Roswell Airport

Wilderness Area Dairies, feedlots,

goat and sheepranches are the major nearbyagricultural sources

farms

farms

farms

grasslands

grasslands

#S

#S

#S

#S#S

Bosque del ApacheWA

Salt Creek WAWhite Mountain WA

Guadalupe Mountains NP

San AndresNational Wildlife Refuge

White Sands

Carlsbad Caverns NP

Samalayuca Dunes

40 0 40 80 MilesN

Dust sources in southern NM

More playas

Ag lands

Ag lands

Ag lands

Ag lands

Yellow shaded areas are locations of potential dust sources

Salt Creek

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Max Gust (mph)

Fine

Soi

l Con

c (µ

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Hourly maximum gust during the sample dayfor all IMPROVE samples

(knots)

Gust not reported for these points

Salt Creek

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0 5 10 15 20 25 30 35 40

Max Hourly Wind Speed (mph)

Fine

Soi

l Con

c (µ

g/m

3 )

Maximum hourly wind speed during the sample dayfor all IMPROVE samples

(knots)

Salt Creek

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Mean 24-hour Wind Speed (mph)

Fine

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Mean 24-hour wind speed during the sample dayfor all IMPROVE samples

(knots)

Can see somewhat of a threshold here

Dust Emission/Wind Correlations

• Next step is to apply this exploratory method to many sites and flush out

• Use coarse mass in addition to fine soil• Working on a code in Access to run query

and generate plots of wind vs dust concentration

• Coordinate with the spatial analysis to catalog events

Asian Dust Analysis

On April 19, 1998, a big Asian dust storm was generated over the Gobi Desert by springtime cold low pressure systems descending from the northwest. It crossed the Pasicic ocean, and subsided to the surface of the western United States around April 29

Comparison of aerosol properties on April 29, 1998 and the averages of year 1998 and 2001

Date Sites Al/Ca Al/Si Ca/Si Fe/Si K/Fe CM/Soil4/29/1998 Worst Case Day Sites-17 Average 2.1 0.52 0.25 0.29 0.59 2.11

STDEV 0.3 0.06 0.03 0.04 0.07 0.94

Year 2001 worst dust days Average 1.4 0.31 0.22 0.27 0.67 7.10

Year 2002 worst dust days Average 1.7 0.43 0.25 0.25 0.72 16.02

17 of the WARP IMPROVE monitoring sites were in 20% worst case days on April 29, 1998. The ratios of Al/Si, K/Fe, AL/Ca and CM/Soil are quite different to the average numbers.

Asian Dust Signatures

• Al/Ca = 2.1 + 0.3• K/Fe = 0.59 + 0.07• Al/Si = 0.52 + 0.06

Rating Each Worst Dust Days• Score = 1 / (Zscore %Uncertainty of Measured Ratio)

Zscore = |Measured Ratio – Mean Asian Dust Ratio| / SQRT(Uncertainty of Measured Ratio^2 + Standard Deviation of Asian Dust Ratio^2)

%Uncertainty of Measured Ratio = SQRT(%Uncertainty of A^2 + %Uncertainty of B^2)

The higher the score, the higher the confidence that the measured ratios are close to the Asian dust ratios based on data from April 19, 1998 Asian dust storm

Number of sites with Score > 2000 in the Year 2001

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1115

4/16/2002

5/10/2001

Figure 3. Satellite images in China (top) and US(Bottom) on April 6 and April 16, 2001, respectively.

• On April 7, The NRL dust model shows the dust cloud emerging from the Gobi desert

• A week later, part of the dust cloud passes over N.America toward the Atlantic

Figure 7. NRL aerosol model outputs on May 10 2001

Number of sites with Score > 2000 in the Year 2001

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0117

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0321

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0426

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0707

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0731

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0827

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0926

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1107

4/26/2002

5/8-11/2002

Figure 8. NRL aerosol model outputs on April 26 2002