ARL-TN-0702 ● SEP 2015

US Army Research Laboratory

Measured In Situ Atmospheric Ambient 

Aerosol Size-Distributions, Particle 

Concentrations, and Turbulence Data for RSA 

TA-6 Test Range, Redstone Arsenal, AL, 

April–May 2015

by Kristan Gurton, Stephanie Cunningham, and 

Edward E Montgomery

Approved for public release; distribution unlimited.
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ARL-TN-0702 ● SEP 2015

US Army Research Laboratory

Measured In Situ Atmospheric Ambient 

Aerosol Size-Distributions, Particle 

Concentrations, and Turbulence Data for RSA 

TA-6 Test Range, Redstone Arsenal, AL, 

April–May 2015

by Kristan Gurton

Computational and Information Sciences Directorate, ARL

Stephanie Cunningham and Edward E Montgomery

USASMDC/ARSTRAT Technical Center, Redstone Arsenal, AL

Approved for public release; distribution unlimited.
ii

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1. REPORT DATE (DD-MM-YYYY)

Sep 2015

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05/2015

4. TITLE AND SUBTITLE

Measured In Situ Atmospheric Ambient Aerosol Size-Distributions, Particle 

Concentrations, and Turbulence Data for the RSA TA-6 Test Range, Redstone 

Arsenal, AL, April–May 2015

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Kristan Gurton, Stephanie Cunningham, and Edward E Montgomery

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

US Army Research Laboratory

ATTN: RDRL-CIE-S

2800 Powder Mill Road

Adelphi, MD 20783-1138

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ARL-TN-0702

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12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release; distribution unlimited.

13. SUPPLEMENTARY NOTES

14. ABSTRACT

This report documents a series of in situ measurements designed to characterize atmospheric effects that influences 

electromagnetic (EM) propagation (i.e., ambient aerosol loading and optical turbulence), during the 5-day periods of 

April 20–24 and May 4–8, 2015, at the RSA TA-6 Test Range, located at Redstone Arsenal, Alabama. Specific aerosol 

parameters presented in this report include, ambient aerosol size distributions (0.54 μm < diameter <20 μm), aerosol particle 

concentrations (#/cm3

), and submicron number density (diameter <0.54 μm). In addition, we present a measure of the 

magnitude of the optical turbulence, i.e., the refractive index structure parameter, Cn

2

, which was measured along a horizontal 

path approximately 2 m above the surface of the site. Also presented are the corresponding meteorological conditions that 

influence the formation of ambient aerosols and that influence the relative strength of the optical turbulence at the site, e.g., 

temperature, relative humidity, and visibility.

15. SUBJECT TERMS

Electromagnetic (EM) propagation, aerosols, optical turbulence, particles

16. SECURITY CLASSIFICATION OF:

17. LIMITATION

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 ABSTRACT

UU

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 OF 

 PAGES

26

19a. NAME OF RESPONSIBLE PERSON

Kristan Gurton

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301-394-2093

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iii

Contents

List of Figures iv

Acknowledgments vi

1. Site Measurement 1

2. Data 2

3. Summary and Conclusion 16

Distribution List 18
iv

List of Figures

Fig. 1 Photograph of RSA TA-6 field site and location of the APS 

spectrometer...........................................................................................1

Fig. 2 Ambient particle concentrations (#/cm3) recorded at RSA TA-6 Test 

Range during the week of April 20–24, 2015. Note the identified fog 

event at 12:20 am on April 24, 2015......................................................2

Fig. 3 Ambient particle concentrations (#/cm3) recorded at RSA TA-6 Test 

Range during the week of May 4–7, 2015. Note the identified fog 

events in the early hours of May 5–7, 2015...........................................3

Fig. 4 Daily average size distributions for the week of April 21–25, 2015. 

Please note fog event recorded during the early morning of April 24, 

2105........................................................................................................4

Fig. 5 Daily average size distributions for the week of May 4–7, 2015. Please 

note fog events recorded during the early morning hours of May 4, 6, 

and 7, 2105.............................................................................................5

Fig. 6 Small particle count (d < 0.54 μm) recorded at RSA TA-6 Test Range 

during the week of April 20–24, 2015...................................................5

Fig. 7 Small particle count (d < 0.54 μm) recorded at RSA TA-6 Test Range 

during the week of May 4–7, 2015 ........................................................6

Fig. 8 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on April 20, 2015 ...................................................................................6

Fig. 9 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on April 21, 2015 ...................................................................................7

Fig. 10 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on April 22, 2015 ...................................................................................7

Fig. 11 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on April 23, 2015 ...................................................................................8

Fig. 12 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on April 24, 2015 ...................................................................................9

Fig. 13 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on May 4–5, 2015. Note artificial aerosol events in the morning 

(approx. 7:00 am) and late afternoon due to movement of vehicles as 

the field test gets set up........................................................................10

Fig. 14 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on May 6, 2015. Please note: The obvious aerosol events at 7:22 am 

and later in the afternoon were a result of vehicular travel along the 

road that boarders the TSI aerosol probe. ............................................11
v

Fig. 15 Ambient aerosol size distribution measured at RSA TA-6 Test Range, 

on May 7, 2015. Please note: The obvious aerosol events at 7:06 am 

was a result of vehicular travel along the road that boarders the TSI 

aerosol probe........................................................................................12

Fig. 16 Measured refractive index structure parameter, Cn

2

, for the week of 

April 20–24, 2105 ................................................................................13

Fig. 17 Measured visibility (miles), air temperature (°C), and relative humidity 

(%), for the week of April 20–24, 2105...............................................14

Fig. 18 Measured refractive index structure parameter, Cn

2

, for the week of 

May 4–8, 2105. Please note the refractive structure parameter data for 

May 7 was omitted due to technical problems.....................................15

Fig. 19 Measured visibility (miles), air temperature (°C), and relative humidity 

(%), for the week of May, 4–8, 2105...................................................16
vi

Acknowledgments

We would like to thank the staff of RSA TA-6 Test Range, Redstone Arsenal, for 

their exceptional support during the test period in which this study was conducted. 

We would also like to thank Mr TG Henderson and Dr Justin Munsell for providing 

the metrological and turbulence data presented in this report. 
1

1. Site Measurement

During the 5-day periods of April 20–24 and May 4–8, 2015, a series of 

measurements designed to characterize various aerosol and atmospheric parameters 

were made in support the All Weather Tracker (AWT) Experiment that was 

conducted at the RSA TA-6 Test Range, located at Redstone Arsenal, Alabama. 

Since the primary objective of the experiment was to investigate both active and 

passive polarimetric imaging methods in the short-wave infrared (SWIR), efforts 

were taken to characterize the 2 atmospheric effects that most influence efficient 

electrometric (EM) propagation, i.e., ambient aerosols and optical turbulence.

Aerosol measurements were conducted using a TSI aerodynamic particle sizing 

(APS) spectrometer, Model 3321 that provides high-resolution, real-time 

aerodynamic measurements of aerosol particle diameters within the range 0.5 to 

20 microns. The aerosol probe was located in the field approximately 500 m from 

the source trailers that were used for the optical experiments. The aerosol 

spectrometer was operated 24/7 during each test period in order to characterize 

diurnal variations in the formation of ambient aerosols. The ambient aerosol 

parameters were continuously monitored using a 10-min sample window, in which 

particles were sized and counted for the specified period. The photograph shown in 

Fig. 1 show the RSA TA-6 test range and the approximate location of the TSI 

particle sizing spectrometer. 

Fig. 1 Photograph of RSA TA-6 field site and location of the APS spectrometer
2

2. Data

The aerosol measurements showing the overall particle concentrations (#/cm3), 

daily averaged size distributions, submicron (fine) particle counts (within a 10-min 

sample), and the diurnal variation of the ambient size distributions, are shown in 

Figs. 2–15.

Fig. 2 Ambient particle concentrations (#/cm3) recorded at RSA TA-6 Test Range during 

the week of April 20–24, 2015. Note the identified fog event at 12:20 am on April 24, 2015. 
3

Fig. 3 Ambient particle concentrations (#/cm3) recorded at RSA TA-6 Test Range during 

the week of May 4–7, 2015. Note the identified fog events in the early hours of May 5–7, 2015. 
4

Fig. 4 Daily average size distributions for the week of April 21–25, 2015. Please note fog 

event recorded during the early morning of April 24, 2105. 
5

Fig. 5 Daily average size distributions for the week of May 4–7, 2015. Please note fog events 

recorded during the early morning hours of May 4, 6, and 7, 2105. 

Fig. 6 Small particle count (d < 0.54 μm) recorded at RSA TA-6 Test Range during the 

week of April 20–24, 2015
6

Fig. 7 Small particle count (d < 0.54 μm) recorded at RSA TA-6 Test Range during the 

week of May 4–7, 2015

Fig. 8 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on April 20, 

2015
7

Fig. 9 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on April 21, 

2015

Fig. 10 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on April 22, 

2015
8

Fig. 11 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on April 23, 

2015
9

Fig. 12 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on April 24, 

2015
10

Fig. 13 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on May 4–5, 

2015. Note artificial aerosol events in the morning (approx. 7:00 am) and late afternoon due 

to movement of vehicles as the field test gets set up. 
11

Fig. 14 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on May 6, 

2015. Please note: The obvious aerosol events at 7:22 am and later in the afternoon were a 

result of vehicular travel along the road that boarders the TSI aerosol probe.
12

Fig. 15 Ambient aerosol size distribution measured at RSA TA-6 Test Range, on May 7, 

2015. Please note: The obvious aerosol events at 7:06 am was a result of vehicular travel along 

the road that boarders the TSI aerosol probe. 

Figures 16–19 shows the turbulence and metrological data.
13

Fig. 16 Measured refractive index structure parameter, Cn

2

, for the week of April 20–24, 

2105
14

Fig. 17 Measured visibility (miles), air temperature (°C), and relative humidity (%), for the 

week of April 20–24, 2105
15

Fig. 18 Measured refractive index structure parameter, Cn

2

, for the week of May 4–8, 2105. 

Please note the refractive structure parameter data for May 7 was omitted due to technical 

problems. 
16

Fig. 19 Measured visibility (miles), air temperature (°C), and relative humidity (%), for the 

week of May, 4–8, 2105

3. Summary and Conclusion

A simple comparison conducted between the weeks of April 20–24 and May 4–7, 

2015, show an obvious increase in aerosol mass that is best seen by comparing the 

aerosol concentrations shown in Figs. 2 and 3. One can only speculate on the exact 

cause, but it is well known that there is a seasonal transition from early to midspring in which ambient aerosol characteristics in rural environments are quite 

dynamic. Also lending to the uncertainty was the noted mowing of grass at the field 

site during the week of May 4–7, 2015, which undoubtable affected the overall 

particle concentration and number densities measured during that week. Similarly, 

the aerosol probe (particle sizer) was affected by transient events due to vehicle 

movement around the RSA TA-6 Test Range, see Figs. 14 and 15, for example. 

Observation of the daily average size distributions (where the transient events have 

been omitted), which are shown in Figs. 3 and 4, show a degree of consistency from 

day to day, and even week to week. The exceptions, of course, take place during 

the evening/early morning hours of April, 24, and May, 5, 6, and 7, in which fog 

event(s) were observed at which time air temperatures fell to a minimum and 

relative humidity climb to 100%. Under these condition warm water vapor (relative 
17

to the particle) condense on the nuclei particles, which causes the aerosol particle 

to grow in diameter, see Fig. 5. 

Figure 4 clearly shows the formation of fog generated particles (small nuclei 

particle encapsulated by water) resulting in a significant increase in the number of 

submicron particles, mid-size particle (4–9 μm range) and large particle >20 μm. 

Finally, we should note the consistent form of the daily variation in the measured 

refractive index structure parameter, Cn

2

, shown in Figs. 16 and 18. As one can see 

in the figures, optical turbulence is generally less in the evening hours as compared 

to the daytime, decreases to a minimum during dusk and dawn, and reaches 

maximum intensity during the afternoon hours. Finally, all data presented in this 

report will be made available in ASCII form to any interested parties upon request 

to the authors. 
18

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