Armosphmc Enur~~nmenr Vol IO. pp. 813 -825. Pergamon Press 1976. Printed in Great Britam 

FREQUENCY AND DIURNAL VARIATION OF DUST 

STORMS IN THE CONTIGUOUS U.S.A.* 

M. M. ORGILL and G. A. SEHMEL 

Atmospheric Sciences Department, Battelle, Pacific Northwest Laboratories, Richland. 

WA 99352, U.S.A. 

(First received 8 January 1976 and in final form 19 March 1976) 

Abstract-Studies of regional wind erosion and the translocation of suspended particles are important 

for accurate surveys of air pollution. This category of investigation has nationwide implications for 

planning and regulatory purposes. However, most regional studies of wind suspension (airborne dust) 

have centered around the Great Plains without much consideration given to other areas of the country. 

The purpose of this study is to quantitate the wind translocation problem throughout the contiguous 

United States by using visibility as an index. National Weather Service and military surface observations 

on dust were analyzed for annual, monthly and diurnal periods. Frequency of dusty periods were 

based on hourly weather observations from stations recording dust, blowing dust, and blowing sand 

when visibility was 7 miles or less. 

Mountainous, forested, and predominantly maritime regions are generally free from major dust 

storms. The highest dust frequency is in the Southern Great Plains. Secondary dust frequency maxima 

occur in the Western States, Northern Great Plains, southern coastal Pacific and inland valleys and 

the Southeast. 

Maximum dust frequency occurs in early and late spring months for most regions but some regions 

experience additional dust in summer or fall. Hourly observations show higher dust frequencies occur 

in the afternoon between 12.00 and 20.00 LST, or during the period of maximum thermal instability. 

Regional dust frequency patterns are discussed in relation to the principal factors which govern 

natural wind-caused suspension, i.e. (1) surface properties, (2) particle properties, and (3) meteorological 

conditions. 

INTRODUCTION 

Studies concerning regional wind translocation of soil 

particles are important to better understanding of air 

pollution processes. Selection of sites for future energy 

installations and related facilities must include thorough consideration of the location’s potential for 

wind resuspension of pollutants. There are diverse 

regions in the United States subject to varying 

degrees of suspended dust. The regional processes of 

particulate resuspension should be understood. Planning for the nation’s energy needs should incorporate 

all possible strategies for control of environmental impacts through competent regulatory and design criteria. Thus it is vital that the frequency, duration and 

intensity of suspended dust episodes be determined 

for candidate sites, as well as existing locations of 

energy-related activity. 

Most wind translocation dust studies have centered 

around the Great Plains (Hagen and Woodruff, 1973) 

with little attention given to other regions of the 

country. Other regions are generally known to experience significant dust storms (Clements et al., 1963; 

Orgill et al., 1974) but there are no comprehensive 

reports concerning the frequency and regional distributions of suspended dust for the entire country. Consequently, the major purpose of this research was to 

quantitate the relative frequency and location of wind 

*This paper is based on work performed under U.S. 

Atomic Energy Commission Contract No. AT(45-l)-1830. 

translocation regions throughout the contiguous 

United States. 

Two methods were considered for analyzing the 

existing data for regional dust frequency. The first 

required examination and analysis of actual airborne 

particulate-concentration data from national and 

local air pollution monitoring stations during suspended dust episodes. Although this method would 

probably be best quantitatively, it was not selected 

for this initial study because of the time and expense 

of collecting and analyzing the vast amounts of data. 

The second method, which was ultimately used, utilized the National Weather Service and Armed Services summarized surface hourly observations of dust 

and prevailing visibility to define regional dust frequencies. This method was more qualitative, but the 

data base for a 15-30 y period could be handled more 

economically and analyzed easily. Consequently, 

National Weather Service, Air Force, Navy, Army 

and Marine summarized surface hourly observations 

on blowing dust and sand were analyzed for annual, 

monthly, and diurnal periods. 

In weather observing practice (Huschke, 1969) a 

dust storm is only reported if blowing dust reduces 

visibility below 5/8 mile (1 km). However, in this 

study we will use the term “dust storm” to include 

all dust events that reduced the prevailing visibility 

below 7 miles (11.3 km). 

The frequency and spatial distribution of dusty 

periods were based on summarized hourly weather 

813 
814 M. M. ORGILL and G. A. SEHMEL 

observations from 343 weather observing stations that 

recorded dust, blowing dust, and sand when the visibility was less than 7 miles (11.3 km). This distance 

is a standard weather observing procedure (NOAA, 

1970). The collected and analyzed data showed, with 

some exceptions, most regions of the continental 

U.S.A. are susceptible to airborne dust due to wind 

translocation. 

PROCEDURES 

Visibility, as a measure of atmospheric opacity, is 

perceived by an observer to be an indicator of the 

quantity of pollution (in this case, dust) in the air. 

Prevailing visibility is the greatest visibility equaled 

or exceeded throughout one-half of the horizon circle 

(NOAA, 1970). It is a subjective measurement which 

depends upon individual ability to both detect and 

recognize distant objects seen against the horizon sky 

by day or to detect distant lights at night. Prevailing 

visibility is taken routinely at National Weather Service observation stations and military installations 

that have observers on duty. 

Charlson (1969) has shown that prevailing visibility 

and particulate concentrations are approximately 

related when the particle size distribution remains 

constant and the relative humidity is less than 70% 

or deliquescent particles are not present in significant 

numbers. 

A theoretical visibility-concentration relationship 

(Hagen and Woodruff, 1973) can be derived by 

assuming: (1) visibility is reduced only by scattering; 

(2) airborne particles are of uniform size; and (3) the 

scattering area coefficient is constant. In this case, 

C = y (mg me3), (1) 

where V is prevailing visibility in km. A nearly identical empirical visibility-concentration relationship at 

1.8 m above the surface was found by Chepil and 

Woodruff (Hagen and Woodruff, 1973) 

C = $$(mgmm3). 

This empirical concentration-visibility relation agrees 

with the theoretical relation when V is about 1 km, 

but has a smaller concentration than the theoretical 

one for visibilities greater than 1 km. 

National Weather Service and military surfade 

observations of dust are only reported when the prevailing visibility is less than 7 miles (11.3 km). If the 

assumptions are met, substitution of 11.3 km into 

equations (1) and (2) gives a dust concentration from 

* The shaded regions of Figs. 2, 5a-d represent regions 

where no hourly observations were found with visibility 

~7 miles due to dust, etc. If dust storms with visibility 

>7 miles were to be included, the relative dust frequency 

would be higher but the location of dusty areas should 

not change significantly. 

2.7 to 5.1 mg mm3. Unfortunately, this criteria eliminates any consideration of dust storms with visibility 

greater than 7 miles or with dust concentrations 

between 75 pg rnw3 (ambient air standard) and 

2700 pg me3. If these data could be included they 

would increase the relative frequency of dust storms, 

but it is not known whether the relative frequency 

distributions of the > 7 mile dust storms are the same 

as the ~7 mile dust storms. We suspect not, but we 

don’t have the data on hand to verify it. Therefore, 

dust frequency data based on prevailing visibility refer 

only to dust storms when the dust concentration is 

from 3 to 5mgm-’ or greater. Measured dust concentrations in dust storms have been reported from 

0.1 to 176 mg me3 depending on stage of storm development (Gillette et al., 1972; Shinn et al., 1974; 

Viletto and Ohman, 1972). 

Hourly observations of prevailing visibility and 

occurrence of dust have been collected over several 

years and are available either from tabulated summaries (Part A) or magnetic tapes at the National 

Climatic Center in Asheville, North Carolina. Tabulated summaries were obtained for 249 weather 

stations and an additional 94 summaries were 

specially processed for this research program by the 

National Climatic Center. Hence, tabulations for 343 

weather stations were utilized in this study. Figure 

1 shows the distribution of stations. 

The data for individual weather stations were tabulated in terms of percentage frequency of occurrence 

for various weather elements for annual, monthly, and 

3-h periods. Data pertaining to percentage frequency 

of dust were extracted, plotted and analyzed. 

The country was divided into seven different 

regions (Fig. 1) depending partially on relative dust 

frequency, spatial dust frequency patterns and geography. To quantify the dustiness in these seven regions 

a simple regional average dust frequency was defined 

as follows: 

i=N c 

RADF = .x’ ;, 

i= 1 

where RADF is the annual or monthly regional average dust frequency;J is the annual or monthly percent frequency of dust occurrence for the ith station 

in each region, and N is the total number of stations 

for each region. 

RESULTS 

Annual distribution of suspended dust and sand 

The frequency of occurrence of suspended dust or 

sand from major dust storms on an annual basis for 

the country (excluding AK and HI) is shown in Fig. 

2. In this figure, frequency isopleths approximate the 

regional dust frequency. The isopleths were drawn 

subjectively with the goal of delineating dust frequency on a broad regional basis. These isopleths 

range from N (none)* to 3% of the total hourly observations. 
Dust storms in the contiguous U.S.A. 815 

North central l 

Fig. 1. Distribution of 343 weather observation stations used in study and seven defined dust regions 

of the country. Dash lines represent the Appalachian Mountains. 

Fig. 2. Annual % frequency of dusty hours based on hourly observations from 343 weather observation 

stations that recorded dust, blowing dust and sand when prevailing visibility was less than 7 miles 

(11 km). Shaded areas (N) represent no observations of dust. Total period between 1940 and 1970, 

approx. 
816 M. M. ORGILL and G. A. SEHMEL 

The occurrence of suspended dust is relatively infrequent. For example, the maximum annual percentage 

frequency for the country is 3.1% at Lubbock, TX. 

This amounts to a total of 5 133 h in a 23-y period 

(105 580 h of observation) or 223 dust h y-l on the 

average. 

A general description of the distribution of annual 

dust frequency in the seven general regions of the 

country as shown in Fig. 2 follows: 

Pacific coast region. Coastal and inland valley 

regions (west of the Cascade Mountains) of WA and 

OR have very few occurrences of major dust storms 

because of the prevailing onshore winds and frequent precipitation, although, strong winds 

(> 7 m s-l) do occur at times. The major areas of 

relatively high incidence are found in the San Joaquin 

Valley (0.24.8x) and Los Angeles basin of CA 

(0.14.4”/,. In central and Southern CA, dutit frequency gradients are very steep, due in part to the 

mountain ranges. 

Rocky Mountain Region. Dust frequency is highest 

in the broad river valleys, deserts, and leeside areas 

of mountain ranges, such as the Mojave Desert in 

southern CA and AZ (0.74.8”/,), Great Salt Lake 

Desert (0.3%), western NV (0.3%), east’ern WA 

(0.1-0.2x) Snake River Valley (0.1x), southern Rio 

Grande Valley (O&> I%), and the higher desert plateaus of AZ (-0.2%) and WY (-0.05%). 

Southern central region. The highest annual dust 

frequency (l-3%) in the country is located along a 

north-south axis, through west TX, OK, KS, and 

eastern CO, approx. 300 km east from the crest of 

the Rocky Mountains. Further east, the frequency of 

dust (- 0.1%) decreases by a factor l&30 in the states 

of MO, AR and LA. 

North central region. The north-south axis of high 

dust frequency from the south central region also 

extends through central NB and eastern S and ND, 

but with lower frequencies. A secondary maximum 

(0.6%) is located in eastern ND. An eastward extension of high dust frequency extends from this area 

through MN toward MI. 

Great Lakes region. The northern Great Lakes area 

has a very low dust frequency (0.05% to N) but areas 

south of the Great Lakes in IL, IN, and OH have 

an increased incidence (0.0254.1%) of dust. Evidently, 

a major part of the suspended dust that occurs in 

the Great Lakes area are due to “dust fronts” moving 

east from the south central regioli and north central 

region (Cohen and Pinkerton, 1966). 

Southeastern region. The southern states, as well as 

TN, KY, WV, and VA have annual dust frequencies 

(0.1-0.2”/,) comparable to some western mountain 

regions. Frequencies are low along the Applachian. 

Mountains, but maximum frequency (0.14.2x) areas 

occur through TN, KY, GA, and the Carolinas. 

Again, “dust fronts” from the south central region 

contribute to the dust frequency in this area. 

Northeastern region. Dust frequency is very low 

(O.oO~.Ol%) in the northeastern portion of the 

Table 1. Annual average regional dust frequency for seven 

regions of the U.S.A. 

South central region 0.61 

Rocky Mountam region 0.17 

North central region 017 

Pacific coast region 0.07 

South eastern regton 0.06 

Great Lakes region 0.04 

North eastern region 0.0 I 

country, and especially along the Applachian Mountains. The urban area between Boston and Washington, D.C., indicates a minor high frequency 

(O.OO%O.lo/,) area of dustiness. The authenticity of this 

feature may be questionable and requires further 

verification. 

A comparison of relative average dustiness of the 

seven regions was made by computing an annual 

average regional dust frequency from equation (3) for 

each region. These are shown in Table 1. 

Comparison of the annual average dust frequency 

for the seven regions shows that the south central, 

Rocky Mountains, and north central regions of the 

country have the highest relative dust frequency. The 

northeast and Great Lakes regions the lowest frequency. The relatively high frequency of dustiness for 

the Pacific coast region is due solely to the influence 

of Central and Southern CA. The coastal regions of 

OR, WA, and NC have one of the lowest (if not the 

lowest) dust frequency in the nation. 

40 m)NrH OF MAXIMUM FREQUENCY 

OF AIRBORNE DUST 

ia 

a 

JAN FEE AWR APR WY JUN JUL AUC SEP CC1 WV DEC JAN 

MONTH 

Fig. 3. The % of observation stations that have a maximum frequency of airborne dust during a particular 

month. 
Dust storms in the contiguous U.S.A. 

KNOXVILLE. TENNESSEE CHATTANOOGA. TENNESSEE 

817 

BRISTOL. SMYRNA. TENNESSEE TENNESSEE 

k 

a4 NONE 

a6 

FE6 

a4 

82 

MAR a4 

a2 

APR ;; 

a4 

MAY 

a2 

a4 

SEP 

a2 

a4 

OCT a2 

NOV ,“: NONE 

I 

a 

DEC NONE 

IiIIII 

a4 

a2 

@HZ M-L-@ 12-14 18-20 

m-6 09-11 15-17 21-23 

TIM 

DATA RECORD: IW-1964 

Ad4 

a2 

APR 

a4 

a2 

a4 

WY 

a2 

a4 

‘UN 

a2 

(16 

JuL a4 

a2 

a4 

0CTa2 

NONE 

a4 

NOV 

a2 

NONE 

(16 

DEC 

a4 

a2 

116 

DEC 

a4 

(16 

OEC 

a4 

a2 a2 

OH?2 W-03 12-14 18-20 Go-a? M-c6 12-14 18-20 m-02 06-08 12-14 18-20 

m-c5 09-U 15-17 n-n m-05 09-11 15-17 21-D m-c6 lx-11 15-17 21-23 

TINE TIME TIME 

DATA RECORD: lW8-1960 DATA RECORD: 1948-1964 DATA RECORD: lp12-1%6 

a4 

JAN 

a2 

NONE 

I 

(16 

FEB a4 

a2 

MARa4 

a2 

hwa4 

a2 

(16 

JUL a4 

a2 

a4 

SEP 

a2 

a4 

OCTaz 

a4 

NOV 

a2 

a4 

JAN 

a2 

(16 

FE8 a4 

a2 

MARa 

a2 

A,,;: 

a4 

“uya2 

a4 

‘UN 

a2 

L16 

JUL a4 

a2 

a4 

AUG 

a2 

a4 

SEP 

a2 

a4 

OCTa2 

a4 

NOV 

a2 

Fig. 4. Four stations in TN showing a definite dust frequency maxima during the Spring months 

as well as diurnal variations. 

Seasonal and monthly variation of suspended dust and 

sand 

The maximum frequency of suspended dust for the 

country occurs during the months of March, April 

and May. Figure 3 shows that during this period 

around 72% of the stations showed maximum 

monthly dust frequencies. In March, 41% of the 

stations indicated monthly maximum dust frequencies. Figure 4 shows four observation stations in TN 

that illustrate a definite spring maximum in dustiness. 

This spring maximum in dustiness is largely the result 

of strong winds (~7 m s- ‘) associated with spring 

cyclonic and convective storm activity. A definite 

afternoon maximum in dust frequency is often 

observed in the spring but this feature will be discussed later. 

A much smaller secondary maximum in dust frequency (4-5x of the stations) occurs during the 

months of September and October. This is the result 

of several stations in the Pacific Coast and Rocky 

Mountain regions having their monthly maximum 

dust frequency during the fall months. This is the case 

in eastern WA and the San Joaquin-Sacramento Valleys of CA. 

The spatial distiibution of the monthly dust frequency for the country are shown in Fig. 5(a-d). One 

of the distinguishing characteristics of the monthly 

dust frequency patterns is the persistence of dust 

source regions west of Mississippi River. The spatial 

dust frequency patterns are generally fixed to certain 

regions of available soil, e.g. Mojave Desert, Great 

Salt Lake Desert, and South Great Plains. 

Regions east of the Mississippi River show intermittent and variable regional dust frequency patterns 

from month to month. During the spring months, 

when the frequency of dust generally increases over 
9 

-0 

6 

a 
Dust storms in the contiguous U.S.A. 819 

Fig. 5. Monthly % frequency of dusty hours for January (a), March (b), July (c) and October (d) 

based on hourly observations from 343 weather observation stations that recorded dust, blowing dust 

and sand when prevailing visibility was less than 7 miles (11 km). Shaded areas (N) represent no 

observations of dust. Other months available from authors. 
820 M. M. ORGZLL and G. A. SEHMEL 

JAN FE8 MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN 

MONTH 

Fig. 6. Monthly regional average dust frequencies for 

seven defined dust regions in the contiguous U.S.A. 

the eastern section of the country, fairly persistent 

maximum dust frequency areas appear in the southeast region including TN and KY. Another maximum 

area occurs through the northern Great Lakes area 

and appears to o~ginate from the north central 

region. By the month of June, these rn~~~ dust 

frequency areas have reduced in magnitude and 

become more variable in location, but still have a 

tendency to persist in the southeast and southern 

Great Lakes region throughout the year. 

A monthly regional average dust frequency was 

computed for each of the seven regions of the country 

for each month by equation (3). The results are presented in Fig. 6. One of the most distinguishing 

characteristics of Fig. 6 is the definite maximum in 

dustiness during the spring months for all areas 

except the Pacific Coastaf region. In this latter case, 

the m~imum occurs during the fall and early winter 

months. All the regions show a definite decrease during the summer months. 

At least three of the regions, south central, Great 

Lakes, and Rocky Mountain, have a seasonal bimodal distribution in dust frequency with a primary 

maximum in the spring months and a secondary 

maximum in the fall or early winter months. Also, 

a number of stations in some of the other regions 

show bimodal dust frequency distributions. Four 

selected stations that show bimodal seasonal dust frequencies are shown in Fig. 7. Each station shows the 

characteristic dust frequency maxima in the spring 

months, the decrease during the summer months, 

another maxima in dustiness during the fall months 

and then another decrease during the winter months. 

Diurnal variation of dust jPequency 

Three-hour dust frequency data were examined for 

a number of stations. The diurnal dust frequency was 

generally classified into four types. These are: (1) the 

afternoon maximum; (2) random; (3) mixed; and (4) 

late afternoon and evening. Examples of these four 

diurnal dust fr~uency types are presented in Fig. 8. 

The afternoon maximum in dust frequency is very 

common and occurs at many locations. Lubbock, TX, 

as well as the stations in Fig. 7 illustrate this diurnal 

variation. The highest dust frequencies occur during 

afternoon hours when the atmospheric boundary 

layer is normally deep and turbulent mixing is more 

pronounced. 

The random diurnal dust pattern is illustrated by 

Lufkin, TX. The dust frequency variation is devoid 

of any significant peaks in dust frequency. In this case 

the dust distribution is probably due to the random 

occurrence of strong winds (>7 m s- ‘) associated 

with frontal or thunderstorm activity. 

The mixed diurnal dust pattern is illustrated by 

Hanford, WA, and Fig. 4. In this case, the random 

occurrence of storm activity is superimposed on an 

afternoon maximum resulting in peak dust frequencies at different local times depending on the month. 

The late afternoon and evening diurnal dust pattern 

is not very common. It appears best developed at 

Bakersfield, CA, between April and August. Apparently, during these warm months a strong sea-breeze 

front invades the Bakersfield area and, at times, produces late evening dust storms of varying degrees 

(U.S. Dept. of Commerce, 19711. 

DISCUSSiON 

The suspended dust potential of a region depends 

on several closely interrelated factors. Factors which 

may influence soil particle translocation are generally 

divided into particle properties, surface properties, 

and meteorological factors (Hilst and Nickola, 1959). 

These factors and their components have been the 

subject of extensive research by soil scientists and 

others for several years. 

Past studies (Viletto and Ohman, 1972; Ohman er 

al., 1972) have attempted to evaluate the potential 

dustiness of an area by examining the particle distribution and physical characteristics of soil. It was concluded that soils with potential dust particles are very 

common on a world basis so other factors such as 

surface cover properties and meteorological factors 

must be factored in to predict dust suspension. Techniques have been developed by soil scientists for estimating soil loss by wind erosion (Woodruff and Siddoway, 1965; Skidmore and Woodruff, 1968), but the 

problem of particle suspension under various surface 

and met~rological conditions has not been completely solved. 
Dust storms in the contiguous U.S.A. 

JAN 

APR 

JUN 

JULY 

LPT 

NOV 

s E~AR~AFE, CALIF. 

r 1 

MB &ca u-14 w2D DM? a-L.8 u-14 Is-20 awK o&63 u-14 i&20 aI-@ 06-m u-14 18-2D 

B-5 D?iI IS-17 a-23 D3-16 OF11 L5-17 21-23 @3-i?J OF11 B-17 a-z? m-m Dwl 15-17 a-t3 

Tlbtt TIKL TIME TIM 

DATA RECORD: 1962-1965 DA~h~CORD: l~Z-1~ OATAR~COff~ l%U-15'70 DATA RECORD: 1992-1967 

Fig. 7. Monthly and 

3 

MAR2 

1 

2 

APR 

1 

JUN 1 

2 

JULY, 

2 

JAN 

1- 

APR 

z1- 

I 

2- 

JUN l2 - 

JUU '1 - 

AU0 

SEPl 

NOV 

% SIOUXCITY. IOWA 

lJ 

2 - 

NOV 

lkd 

2 

APR 

1 

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JUN 

1 

2 

JUL 

1 

SEP 21 

3 

h5AR2 

1 

diurnal dust frequency variations at four locations that have a seasonal bimodal 

distribution of dust frequency. 

An important factor in assessing the dust potential 

of a region is the presence or absence of protective 

vegetation cover. Dense vegetation which is often 

found in the high mountains and in regions of moderate to high precipitation provides excellent protection 

from strong wind movement. Thus, a large share of 

the coastal Pacific northwest, Rocky and App~achi~ 

Mountains, the Great Lakes region, and the northeast region have very low dust frequencies. However, 

dust may be transported from other regions. Table 

2 shows monthly dust frequencies in mountainous 

regions for the available stations. Table 2 generally 

indicates dust frequencies are quite low in mountainous terrain, but dust is not totally absent. Apparently, a large share of the reported airborne dust originates and is transported from local surrounding 

dust source regions. 

When the vegetative cover is disturbed by mechanical means, such as construction, plowing, strip-mining, etc. the regional dust potential is expected to increase. Since the early spring and fall months are normally the time period in which farmland is prepared 

for future crops, vast areas of disturbed soil become 

available for wind translocation. Appar~tly, agricultural activity is a factor that may explain the high 

frequency of dustiness for the whole country during 

the spring months and possibly again during the fall 

months as indicated in Figs. 3 and 6. 

The ground surface characteristics also changes 

during the winter. In the northern states and in the 

mountanous areas the ground may freeze or become 

covered with snow at times. Dustiness is nearly 

nonexistent during this time, but the snow cover itself 

will be subjected to wind translocation. Blowing 
822 M. M. ORGILL and G. A. SEHMET 

* 

a 

LUEBDCK.TEKAS 

6 

MN b 

2 

0 

I 

JAN 

* BAKERSFIELD, CALIF. * LUFKIN. TEXAS 

I 1 I2 

JAN 1 JAN 2t 

6 

FEB b 

2 

0 

10 

a 

MAR 6 

MR 

I 

APR 

4 

* HANFDRD. WASH. 

.6 

.b 

.2 

.D 

.b 

.2 

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.b 

.2 

.O 

.6 

.b 

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.O 

APR 2 

1 

2 

APR 1 

2 

0 

12 

10 

8 

APR 6 

4 

2 

8 

6 

My 4 

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JUN 

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.2 

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.b 

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2 

JUN 

1 

2 

JUN 1 

JULY 1 

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.6 

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2 

JULY1 

2 

0 

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JUN 

2 

I SEPTl 

0 

JULY o 

AIn? 0 2 2 

SEP7 D OCT .2 

DCT 

1 OCT , 

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NW 2 2 2 

i 

NW NW 

.2 1 No” 1 

D 

(8-Q 09-11 I%17 21-23 ws wn u-17 21-23 ows o)-11 ls-17 21-23 

TIM TIhE TIME 

DATARECOW lW-1%7 DATARECORD: 398-1970 DATARECORD: lW8-I%4 

NONE 

E NM 

(B-05 Dell E-17 21-23 

TIM 

DATARECORR 1@9-15W 

Fig. 8. Four types of diurnal dust frequency variations; afternoon maximum: Lubbock, TX; random: 

Lufkin, TX; mixed: Hanford, WA; late afternoon and evening maximum (warm season): Bakersfield, 

CA. 

Table 2. Monthly dust frequency for stations in mountainous areas (% of total monthly or annual hourly observations) 

station Jan. Feb. Mar. Apr. May Jlllle July Aug. Sept. Oct. NOV. Dec. Year 

Montague. CA NOIX N0Ile 

Blue Canyon, CA NOIX NolIe 

Donna Summit. CA NOIX O.l(“) O.Ol(?) 

Baker, OR 0.008 0.016 0.049 0.016 0.007 

Ely, NV 0.036 0 038 0.053 0.254 0.018 0.018 0.053 0.019 0.055 0.019 0.08 1 0.056 

Bryce Canyon. UT 0.126 0.008 0.011 

FlagshIT, AZ 0.068 0.030 0.008 

Ft. Huacbuca, AZ 0.1 0.2 0.1 0.01 0. I 0.035 

Dillon, MT O.GQ9 O.OOR 0016 0.003 

Kalispell, MT 0.016 0.015 0.015 0.031 0.006 

Eanle. CO 0.065 0.063 0.008 0008 0.012 

Asheville, NC 0.035 0.166 0.008 0 024 0.019 

Roanoke. VA 0.026 0.079 0.047 0.013 

Elkins, WV 0104 0.040 0.008 0.012 

Plattsburgh, NY NolIe NolIe 

Burlington, VT 0.015 0.001 
Dust storms in the contiguous U.S.A. 823 

snow, during the winter, is more common than dust. 

Winter monthly frequencies of blowing snow may 

vary between 1 and 12% of the total hourly observations. These frequencies are substantially higher than 

dust frequencies. However, the role of blowing snow 

in the translocation of radioactive particles or other 

potentially hazardous materials has not been investigated. 

Meteorological systems or events that can cause 

major dust suspension throughout the country are: 

1. Convective weather systems, i.e. squall lines, 

thunderstorms, tornadoes. 

2. Warm and cold frontal passage. 

3. Cyclogenesis. 

4. Low-level winds associated with upper-level jet 

streams. 

5. Diurnal winds. 

6. Mountain katabatic winds, e.g. Chinook and 

Santa Ana. 

NEWYORU. NEWY0RKIJ.F.K. AIRPORT WESTHAMPTON. LONG ISLAND 

JAN 

FEE 

MAR 

APR 

JUN 

JUL 

AUG 

SEP 

a: 

a2 

a4 

(18 

a6 

a4 

a2 

a4 

a2 

a4 

a2 

a4 

a2 

art 

a2 

(16 

t 

NONE 

a4 

a2 

a4 

JPd 

a2 

a4 

MAR 

a2 

I18 

(16 

APR 

a4 

a2 

a4 

MAya 

Jet 

WNE 

a4 

JUL 

a2 

a4 

AUG 

a2 

NONE 

a4 

SEP 

a2 

OCTa4 

a2 

(16 

DEC 

a4 

a2 

m-a? M-m u-14 l8-20 

m-G5 w-11 15-17 21-23 

TIME 

DATARECORD: lW-l%S DATARECORD: lW-1%7 

An interesting climatological feature this study has 

revealed is that many relatively high-dust frequency 

areas in the Rocky Mountain region are located in 

the lee of mountain ranges where katabatic winds 

often occur. The phenomenon is well known east of 

the Rocky Mountains and Sierra Nevadas, and also 

occurs in varying degrees in other locations, such as 

eastern WA, western NV, western and eastern UT, 

the WY desert and the southern Rio Grande Valley. 

This climatic feature is not so apparent east of the 

Mississippi River unless the dust frequency maximum 

which occurs during the spring months in eastern S 

and NC is the result, in part, to the leeside effects 

of the Appalachian Mountains. 

The Los Angeles Basin and southern San Joaquin 

Valley is also another region where katabatic winds 

cause dusty conditions. Warm, dry and dusty Santa 

Ana winds blow from the Mojave Desert westward 

into this region, causing severe dust conditions at 

times. The maximum dust frequency during the late 

CHICOPEEFALLS. MASSACHUSETTS FALAWUTH. MASSACHUSETTSlOTlSA 

NO?“, 

a6 

DEC 

a4 

a2 

Ln-@%-!ze 12-Y 18-2il 

m-a G9-11 1.517 21-a 

TIME 

DATA RECORD: lpll-1%7 

a: 

JAN 

a2 

04 

FEB a2 

a4 

MAR 

a2 

(18 

06 

APR 

a4 

a2 

a4 

mAYa 

JUNG4 

a2 

a4 

JUL 

a2 

a4 

AUGa2 

a4 

SEP 

a2 

(16 

DEC 

a4 

a2 

OI-LQ t-6-13 12-14 18-20 

m-m w-1, u-17 21-B 

TINY 

DATA RECORD: 1pb2-1970 

Fig. 9. Monthly and diurnal dust frequency at selected east coast locations 
824 M. M. ORGILL and G. A. SEHMEL 

DOVER, DEtAWARE 

a6 

a4 

APR 

a2 

a4 

MAY 

a2 

JUN i”, 

a6 

JUL a4 

a2 

a4 

AUC a2 

a4 

SEP 

a2 

DEc t&LLJ IX-CQ M-OB 12-14 18-20 

m-G5 09-11 15-17 21-23 

TIME 

DATA RECORD: lp12-1965 

WRIGHTSTOWN, hEW JERSEY 

a2 

a4 

FEE 

a2 

a4 

MARa 

a6 

a4 

APR 

a2 

a4 

MAY 

a2 

JUN a4 

a2 

a6 

JUL a4 

a2 

a4 

SEP 

a2 

NO” ;“2 

(16 

DEC 

a4 

m-m lx-11 l5-17 21-23 

TIME 

DATA RECORD: Ip12-1970 

LAKEHURST, NfW JERSEY 

JAN a4 

a2 

a4 

MARa 

a6 

adAPR 

a4- 

MAY 

azr 

JUN a4 

a2 

NONE 

116 

JUt a4 

a2 

a4 

AUG 

a2 

a4 

SEP 

a2 

a4 

OCTa2 

13-m M-t3 12-14 18-20 

MIDDLETOWN, PENNSYLVANIA 

JAN ” 

a2 

a4 

:EB 

a2 

a4 

MARa 

Q6 

a4 

APR 

Q2 

a4 

MAY 

a2 

JUN a4 

a2 

a6 

JUL a4 

a2 

AUG 

a4 

rJ.2 

SEP a4 

a2 

a4 

CCT 

a2 

NOV;; 

OS-t6 W-11 15-17 21-23 LB-05 09-n 15-17 21-o 

TIME TIME 

DATA RECORD: 1945-1972 DATA RECORD: 1935-1%7 

Fig. 10. Same as Fig. 9, but for 4 different locations. 

fall and early winter months (Fig. 6) within the Los 

Angeles Basin is the result, in part, to these dusty 

Santa Ana events. 

A surprising aspect of this study was the presence 

of dust events in the eastern section of the country, 

especially between Washington, D.C. and Maine. 

Figures 9 and 10 are a selection of observation 

stations in this region that indicated dust episodes 

but at infrequent periods. The origin of the airborne 

dust, if it is actually dust (possibly observers could 

confuse haze and smoke with dust in these relatively 

high polluted regions), is not known at this time. Even 

though eastern dust events are not particularly significant, further confirmation of these episodes may be 

of interest, but would require a detail examination 

of the hourly observation records of several eastern 

stations and the synoptic charts during suspected dust 

episodes. 

CONCLUSIONS 

This study has shown that many diverse regions 

of the country, such as urban, agricultural, desert, valley, plain and forested areas are subject to suspended 

dust in varying degrees. Regions of the country that 

are mountainous, forested and predominantly maritime are generally free from major “dust storms” (visibility less than 11 km). The highest frequency of dust 

is observed in the southern Great Plains. Secondary 

dust frequency maxima are observed in the western 

states, northern Great Plains, southern coastal Pacific 

and inland valleys and the southeast. 

Maximum dust frequency occurs in the early and 

late spring months for most regions of the country, 

but some areas experience additional dust in the summer or fall. Observations show that the higher frequencies of airborne dust occur in the afternoon 
Dust storms in the contiguous U.S.A. 825 

period between 12:00 and 20:00 LST or during the 

period of maximum thermal instability. 

Details on the different regional patterns of dust 

frequency would require additional studies on the 

principal factors which govern natural wind-caused 

suspension, i.e. (1) soil particle properties, (2) surface 

properties, and (3) meteorological conditions. 

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aerosol mass concentration: A Review. Environ. Sci. 

Technol. 3, 913-918. 

Clements T., Mann J. F., Stone R. 0. and Eymann J. L. 

(1963) A study of windborne sand and dust in desert 

areas. Technical Report ES-& Earth Sciences Div., I/S, 

Army National Laboratories. 

Cohen J. M. and Pinkerton C. (1966) . , Widesnread translocation of pesticides by air transport and rain-out. 

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Gillette D. A., Blifford J. H., Jr. and Fenster C. R. (1972) 

Measurements of aerosol size distributions and vertical 

fluxes of aerosols on land subject to wind erosion. J. 

appl. met. 11, 977-987. 

Hagen L. J. and Woodruff N. P. (1973) Air pollution from 

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of small particles. Bull. AMS 40, 73-77. 

Huschke R. E. (Editor) (1959) Glossary of Meteorology, pp. 

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Ohman H. L., Viletto J., Jr., Ackerson K. T. and Miller 

L. L. (1972) Potential sand and dust source areas. Report 

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Orgill M. M., Sehmel G. A. and Bander T. J. (1974) 

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Skidmore E. L. and Woodruff N. P. (1968) Wind erosion 

forces in the United States and their Use in predicting 

soil loss. Agriculture Handbook No. 346, U.S. Dept. of 

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U.S. Dept. of Commerce (1971) Narrative Climatologicaf 

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Viletto J. and Ohman H. L. (1972) Particulate matter considerations in the design of V/STOL Aircraft. Special 

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Woodruff N. P. and Siddoway F. H. (1965) A wind erosion 

equation. Soil Sci. Sot. 29, 602-608. 

AE. 10/10--c