prepared by: ilias kavouras, vic etyemezian, dave dubois, mark green, marc pitchford, jin xu

Preliminary assessment of the principal causes of dust-resultant

haze at IMPROVE sites in the Western United States

Prepared by: Ilias Kavouras, Vic Etyemezian, Dave DuBois, Mark Green, Marc Pitchford, Jin Xu

Division of Atmospheric Sciences, Desert Research Institute

Prepared for: Western Regional Air Partnership, Dust Emissions Joint Forum

Tempe, 11/15/2005

i. Introduction – scope of the studyii. Development of Empirical/Heuristic Approach

(EHA)• Description of tools• Integration into GIS• Interpretation of EHA outcomes

iii. Case studiesiv. Results v. Seasonal and spatial variation of dust sourcesvi. Future studies

Outline

Scope of the studyIdentify events resulting in dust on worst dust days in WRAP

(worst dust day: A 20% worst-case visibility day when dust was the largest contributor)

1. Long-range transport (Intercontinental)

2. Windblown events

3. Upwind transport

4. Undetermined sources

(2) and (3) sources/events were further identified as Local (1 site affected) or Regional (multiple sites affected in the area)

1. Developed an empirical/heuristic approach (EHA) usinga. Elemental concentration ratiosb. Multivariate linear regression analysis c. Air mass backward trajectories;d. Land use/land cover data for US;e. USGS Wind erodibility group (soil erosion metric) for US

2. Use of the EHA to assign worst dust days into a source/eventa. Integrate all tools into a geographical information system (GIS)b. Develop a set of guideline criteriac. Generate maps for each worst dust day

Methodology

April 29,1998: 17 of the WRAP IMPROVE monitoring sites had 20% worst dust days.

Period Elemental ratiosAl/Ca Al/Si Ca/Si Fe/Si K/Fe CM/Soil

Year 2001 1.4 0.31 0.22 0.27 0.67 7.10

Year 2002 1.7 0.43 0.25 0.25 0.72 16.02

April 29, 1998 Mean 2.1 0.52 0.25 0.29 0.59 2.11

St. dev. 0.3 0.06 0.03 0.04 0.07 0.94

Asian Dust

x/y%Ux/yΖΠ1ADS

2refyxσ

2

dayyxU

refyxdayyx

x/yZ

2

100yU

2

100xU

dayyxU

Zx/y is the Z-score for the ratio X/Y;Ux/y is the uncertainty of the ratio X/Yx/yday is the ratio of X/Y during a given day;x/yref is the reference ratio of X/Y estimated based on April 29,1998 event ;σ(x/y) is the standard deviation of reference X/Y ratios and;Ux and Uy are the measurement uncertainties for elements X and Y

Asian Dust Score (ADS)

Reference Asian Dust Ratio (based on 04/29/1998 episode): Al/Ca = 2.1 + 0.3; K/Fe = 0.59 + 0.07; Al/Si = 0.52 + 0.06

AGTI (12/19/02) BIBE (03/09/02) BAND (04/25/01)

Al/Ca 1.02 (0.21) 1.50 (0.13) 1.17 (0.10)

K/Fe 0.61 (0.05) 0.61 (0.04) 0.59 (0.04)

Al/Si 0.32 (0.07) 0.39 (0.03) 0.49 (0.04)

ADS 201 1809 40943

ADS Interpretation

0-750 Small signature; Unlikely Asian dust

750-1500 Moderate signature; Asian dust influence should be considered

> 1500 Strong signature; Asian dust influence is indicated by chemical analysis, confirmation using external tools is required

ADS interpretation

Multivariate linear regression analysis to estimate Locally-

generated Windblown Dust (LWD)eakxkb1kx1kb.....2x2b1x1bepymy

ym is the measured dust mass concentration on a given site and date;yp is the dust concentration estimated by a linear combination of independent variables that describe the wind conditions;b1, b2,……., bk are the regression coefficients of the independent variables;x1, x2,……., xk are the values of independent variables that describe the wind conditions;a is the intercept which corresponds to yp when x1, x2,……., xk are equal to 0 and;ε is the residual error - the difference between the ym and yp

kGkb1kG1kb.....2G2b1G1bLWD

CASTNET AZDEQ

NPSISH

RAWS

NASA

1-h Central Meteorological

Database

•Days with precipitation for more than 10h

•Precipitation occurred after 12:00 p.m.

1-h Modified Central

Meteorological Database

A B

WD1 0o - 90o < 45o or > 315o

WD2 90o - 180o 45o - 135o

WD3 180o - 270o 135o - 225o

WD4 270o - 359o 225o - 315o

Wind speed

WS1 < 14 mph

WS2 14 – 20 mph

WS3 20 – 26 mph

WS4 > 26 mph

WS1 WS2 WS3 WS4

WD1 G1 G2 G3 G4

WD2 G5 G6 G7 G8

WD3 G9 G10 G11 G12

WD4 G13 G14 G15 G16

Σ( (24-h

Database development

24-h Modified Central

Meteorological Database

24-h “Dust” Database

IMPROVE data2001-2003

Regression analysis• Only wind conditions groups corresponding to wind speed higher than 14 miles/hour• Least-squares method• Forward, backward and stepwise variable screening methods• Regression coefficients significant at p-value < 0.10 or 0.15• Regression coefficients with Variance infiltration factor VIF > 10 were rejected• Null hypothesis (H: μ1= μ2=..... = μk= 0) for both regression coefficients and model was

investigated• Only measurements with LWD – 2 standard error 0 were considered

MLRAnalysis

IMPROVE sites where dust/wind relationship exists

Overall: 129 IMPROVE sites 71 sites with available meteorological data43 sites with statistically significant MLRA results41 sites with reliable Local Windblown Dust (LWD) results

Example: Regression coefficients by quadrant

Badlands National Park, SD Bosque del Apache, NM

WD1WS3: 0.438 0.247 WD1WS2: 39.278 8.138

WD2WS3: 2.272 0.694 WD3WS3: 7.924 1.060

WD3WS2: 1.590 0.177

Although regression coefficients can be used to predict the dependent variable using a set of independent variables, it provides no information about the relative contribution of each independent variable because independent variables means and variances were not considered.

The standardized z-score coefficients were estimated, thus all independents variables have mean value of 0 and standard deviation of 1. The standardized regression coefficients (β1, β2,......, βn) provide enough evidence of the relative contribution of the independent variables.

Badlands National Park, SD

Bosque del Apache, NM

Example: Standardized regression coefficients by quadrant

LWD vs. Total Measured Dust

#WDD with predicted LWD / total WDD (number shows the total number of WDD)

Mean LWD / total TMD (number shows the mean dust conc for WDD)

LWD and TMD for reliable MLRA results

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DustWindblown dust

Air masses backward trajectoriesNOAA HYSPLIT trajectory model

For all sites and worst dust days:

Duration: 48-h and 192-hFrequency: Every 3 hours (8:00, 14:00 and 20:00)Resolution: 1 hourStarting heights: 10, 500 and 1500 m.a.g.l.

Trajectory speed (km/h) = distance between two trajectory points• 0 – 14 miles/hour• 14 – 20 miles/hour• > 20 miles/hour

Trajectory endpoint at 8:00 a.m. (CST)"

""

!!

!

###

0.00 < speed < 14.00 mph14.00 < speed < 20.00 mphspeed > 20.00 mph



Trajectory endpoint at 8:00 p.m. (CST)


Trajectories

Air masses backward trajectories

Land use / Land coverNational Land Cover Dataset 1992 (NLCD 1992)

Landsat Thematic Mapper satellite data (U. S. Geophysical Survey and U. S. Environmental Protection Agency)

Resolution: 30 meters

21 classes of land cover (Anderson Land Cover Classification)

11. Open Water12. Perennial Ice/Snow21. Low Intensity Residential22. High Intensity Residential23.Commercial/Industrial /Transportation32. Quarries/Strip Mines/Gravel Pits33. Transitional81. Pasture/Hay82. Row Crops83. Small Grains84. Fallow85. Urban/Recreational Grasses

41. Deciduous Forest42. Evergreen Forest43. Mixed Forest91. Woody Wetlands92. Emergent Herbaceous Wetlands61. Orchards/Vineyards/

51. Shrubland71. Grasslands/Herbaceous31. Bare Rock/Sand/Clay

Data were obtained from: http://landcover.usgs.gov

Land use / Land cover

Land use / Land cover: 3 categories

Wind Erodibility Group (WEG)

.

• Indicator of susceptibility to wind erosion based on:

• soil texture,• organic matter content, • effervescence due to carbonate reaction with HCl, • rock and para-rock fragment content • minerology.• Soil moisture and the presence of frozen soil also influence soil blowing.

. The range of valid entries for wind erodibility group data is 1, 2, 3, 4, 4L, 5, 6, 7, and 8

Source: US Department of Agriculture. National Resources Conservation Services National Soil Survey Handbook: Soil Properties and Qualities (Part 618)

Data were obtained from: http://water.usgs.gov/GIS/dsdl/muid.e00.gz

Wind Erodibility Group (WEG)

Combination of Land Use / Land Cover and Wind Erodibility Group

layers

X =

Human influenced layer

Grass- and shrub-lands layer

Forest s and wetlands layer

Background layer for GIS analysis

Forests & wetlandsLow erodibility based on soil texture High erodibility based on soil texture

Shrubland and grassland areas

Low erodibility based on soil texture

High erodibility based on soil texture

Human-induced areasLow erodibility based on soil texture

High erodibility based on soil texture

Land use and wind erosion

B

Precipitation occurred at the site

! IMPROVE site with a valid sample

Ï IMPROVE site without a valid sample

IMPROVE site

Trajectory endpoint at 8:00 a.m. (CST)"

""

!!

!

###






TrajectoriesAsian Dust Score (only shown for worst dust days)

3 ADS < 7503 750 < ADS < 1500

3 ADS > 1500

Local windblown dust (only shown for worst dust days

§ No Met data

! LWD/TMD = 0.00

! LWD/TMD < 0.25

! 0.25 < LWD/TMD < 0.50

! 0.50 < LWD/TMD < 1.00

! LWD/TMD > 1.00

Representation of multiple linear regression of wind conditions vs. total measured dust available for this site day

Low/moderate erodible forest areas

Low/moderate erodible human-

influenced areas

Moderate/high WEG shrubland areas

IMPROVE site without a valid sample Precipitation occurred

at this IMPROVE site

IMPROVE sites with a valid sample but not a

worst dust day

The ADS is higher than 1500 and the LWD/TMD is lower

than 0.25

The ADS is higher than 1500 and no LWD was calculated

because of no meteorological data

The ADS is not calculated due to absence of reliable

chemistry data and the LWD/TMD is between 0.50

and 1.00The ADS is higher than 1500

and the LWD/TMD is 0.00

No ADS and LWD/TWD were calculated because

meteorological and chemical data were not available

High speed 14:00 trajectory for WICA over moderate/high erodible shrubland

areas that are more than 24 hours away from the site

Moderate speed 8:00 trajectory over low/moderate

erodible shrubland areas

Moderate speed 20:00 trajectory over Mexico

Low speed trajectories at and near the site

Moderate/high speed trajectories upwind of the site

Event/Confidence Level

Educated guess(+)

Somewhat confident(+++)

Very Confident(++++)

1. Asian Dust Case 1: Asian Dust Score Available for site

{Asian Dust score > 1500 at multiple sites}

OR{(Asian dust score >1500 at

one site) AND

(back trajectories suggest air mass originated over Pacific

Ocean)}

Case 2: Asian Dust Score not available for site

{(Asian dust scores at multiple sites surrounding the site of

interest >1500) AND

(back trajectories suggest air mass originated over Pacific

Ocean)}

Case 1: Asian dust score available for site

{(Asian Dust Score > 1500 at multiple sites)

AND (back trajectories suggest air mass originated over Pacific

Ocean)}

Case 2: Asian Dust Score not available for site

{(Asian dust is primary event causing dust at multiple sites

surrounding the site of interest with a confidence of +++++)

Case 1: Asian dust score available for site

{(Asian Dust Score > 1500 at multiple sites

AND (back trajectories suggest air mass originated over Pacific

Ocean)AND

(satellite or models indicate large scale transport of dust

from Asia)}

Asian dust event

Asian dust example (***** for NOAB, SIAN, YELL and ZION)


Educated guess(+)



2. Windblown Dust

Case 1: Meteorological data available and MLRA showed

significant relationship between high wind conditions and dust

measured{(LWD to total measured dust ratio

>0)AND

(Back trajectories show high wind speed (>20 mph) at or near the site

over terrain with moderate or greater wind erodibility)}

Case 2: Meteorological data not available for day of interest but

MLRA showed significant relationship between high wind

conditions and dust measured at site of interest

{(Back trajectories show high wind speed (>20 mph) at the site over terrain with moderate or greater

wind erodibility) AND

(Worst dust days at one or more sites near the site of interest are caused by windblown emission

with confidence of “+++” or higher)}

Case 1: Meteorological data available and MLRA showed

significant relationship between high wind conditions and dust

measured{(LWD to Total measured dust ratio

>0.25) AND

(back trajectories show high (>20 mph) wind speed at or near the site

over terrain with moderate or greater wind erodibility)}

Case 2: Meteorological data not available for day of interest but

MLRA showed significant relationship between high wind

conditions and dust measured at site of interest

{(Back trajectories show high wind speed (>20 mph) at the site over terrain with moderate or greater

wind erodibility) AND

(Worst dust days at one or more sites near the site of interest are caused by windblown emission with confidence of “+++++” or

higher)}

Case 1: Meteorological data available and MLRA showed significant

relationship between high wind conditions and dust

measured{(LWD to total measured dust

ratio > 0.5) AND

(back trajectories show high (>20 mph) wind speed at or

near the site over terrain with moderate or greater wind

erodibility)}

Windblown dust event

Windblown dust example (*****)


Educated guess(+)



3. Transport from windblown dust sources upwind

Case 1: Meteorological data available

ANDNo evidence of local

windblown dust (LWD=o or not calculated)

(back trajectory for site shows up to three hours of high winds (>20 mph) over terrain with moderate or greater wind erodibility within one day of transport of the site)}

OR (back trajectories for multiple

sites shows up to 3 hours of high winds (>20 mph) over terrain with moderate or greater wind

erodibility within one day of transport of the site)}

Case 2: Meteorological data not available for day of

interest but MLRA showed significant relationship

between high wind conditions and dust measured at site of

interest{(back trajectory for site shows up to three hours of high winds

(>20 mph) over terrain with moderate or greater wind

erodibility within one day of transport of the site) but absence of high winds over the site itself}




(back trajectory for site shows up to 8 hours of high winds (>20 mph) over terrain with moderate or greater wind erodibility within one day of transport of the site)}

OR (back trajectories for multiple

sites shows up to 3 hours of high winds (>20 mph) over terrain with moderate or greater wind


Case 2: Meteorological data not available for day of

interest but MLRA showed significant relationship

between high wind conditions and dust measured at site of

interest{(back trajectory for site shows up to eight hours of high winds

(>20 mph) over terrain with moderate or greater wind





(back trajectory for site shows up to 15 hours of high winds (>20 mph) over terrain with moderate or greater wind


Case 2: Meteorological data not available for day of interest but MLRA showed significant

relationship between high wind conditions and dust

measured at site of interest{(back trajectory for site shows up to 15 hours of high winds (>20 mph) over terrain with moderate or greater wind


Upwind transport example (*****)


Educated guess(+)



2-3a. Windblown Dust: Regional

Event

{(Same as for 2 or 3.) AND

{(back trajectories for multiple sites indicate a common regional flow pattern)}

{(Same as for 2 or 3.)AND

{(back trajectories for multiple sites indicate a common regional flow

pattern)}

{(Same as for 2 or 3.)AND

{(back trajectories for multiple sites indicate a common regional flow

pattern)}

Regional windblown or upwind transport events

Regional event example: R1: ZION and BRCA; R2: MEVE and WEMI

prepared by: ilias kavouras, vic etyemezian, dave dubois, mark green, marc pitchford, jin xu

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