Surface Layer Stability Transition Research Maximum 

Time Delay from Sunrise/Non-Ideal Conditions: 

2001 June Case Study 

by Gail-Tirrell Vaucher and Manny Bustillos 

ARL-TR-2823 May 2003 

Approved for public release; distribution is unlimited. 
NOTICES 

Disclaimers 

The findings in this report are not to be construed as an official 

Department of the Army position, unless so designated by other 

authorized documents. 

Citation of manufacturers’ or trade names does not constitute an 

official endorsement or approval of the use thereof. 
Army Research Laboratory 

White Sands Missile Range, NM 88002-5501 

ARL-TR-2823 May 2003 

Surface Layer Stability Transition Research Maximum 

Time Delay from Sunrise/Non-Ideal Conditions: 

2001 June Case Study 

Gail-Tirrell Vaucher and Manny Bustillos 

Computational & Information Sciences Directorate, ARL 

Approved for public release; distribution is unlimited. 

iii 

Contents 

Preface vi

Acknowledgements vii

Executive Summary 1

1. Introduction 2

1.1 U.S. Army Interest in Atmospheric Stability Transition Research .................................2 

1.2 Civilian Interest in Atmospheric Stability Transition Research......................................3 

1.3 Purpose and Overview.....................................................................................................3 

1.4 Background of the Stability Transition Study.................................................................4 

1.5 Character of the Stability Transition ...............................................................................6 

1.6 Ideal and Non-ideal Stability Transition Forecast Standards..........................................8 

2. Seasonal Algorithm Statistical Maximum Test 9

2.1 2001 June Solstice-Atmospheric Surface Layer Test Overview.....................................9 

2.2 Test Execution...............................................................................................................10 

2.3 Test Summary................................................................................................................10 

2.3.1 Characterization of Nighttime, Transition, Daytime Atmospheric Conditions.11 

2.3.2 Unique Neutral Events ......................................................................................11 

3. Discussion of Results 12

3.1 Extended Stability Transitions ......................................................................................13 

3.2 Multiple Stability Transitions........................................................................................13 

4. Conclusion 14

Acronyms 15

References 16

Appendix A: Thompson Tower Data 19
iv 

Appendix B: Rawinsonde Data 37

Report Documentation Page 50 

List of Figures 

Figure 1. Local Sunrise, SRNE Rule of Thumb, and NE Times, 1994 February-1995 June 

(Raw Data)........................................................................................................................5 

Figure 2. SRNE Rule of Thumb, Raw and Monthly Averaged NEs, 1994 February-1995 June....5 

Figure 3. Monthly Averaged Sunrise Neutral Event Time Differences, 1994 April-1995 June .....6 

Figure 4. Coincident Cn

2

, Temperatures, and Insolation Time Series along a 1–km path for 

24 March 2001 at HELSTF, NM ......................................................................................7 

Figure A1. Thompson Tower-2001 June 19: Temperature ...........................................................20 

Figure A2. Thompson Tower-2001 June 19: Relative Humidity ..................................................20 

Figure A3. Thompson Tower-2001 June 19: Wind Speed ............................................................21 

Figure A4. Thompson Tower-2001 June 19: Wind Direction.......................................................21 

Figure A5. Thompson Tower-2001 June 19: Pressure ..................................................................22 

Figure A6. Thompson Tower-2001 June 19: Solar Radiation.......................................................22 

Figure A7. Thompson Tower-2001 June 19: Delta-T ...................................................................23 

Figure A8. Thompson Tower-2001 June 20: Temperature ...........................................................24 

Figure A9. Thompson Tower-2001 June 20: Relative Humidity ..................................................24 

Figure A10. Thompson Tower-2001 June 20: Wind Speed ..........................................................25 

Figure A11. Thompson Tower-2001 June 20: Wind Direction.....................................................25 

Figure A12. Thompson Tower-2001 June 20: Pressure ................................................................26 

Figure A13. Thompson Tower-2001 June 20: Solar Radiation.....................................................26 

Figure A14. Thompson Tower-2001 June 20: Delta-T .................................................................27 

Figure A15. Thompson Tower-2001 June 21: Temperature .........................................................28 

Figure A16. Thompson Tower-2001 June 21: Relative Humidity ................................................28 

Figure A17. Thompson Tower-2001 June 21: Wind Speed ..........................................................29 

Figure A18. Thompson Tower-2001 June 21: Wind Direction.....................................................29 

Figure A19. Thompson Tower-2001 June 21: Pressure ................................................................30 

Figure A20. Thompson Tower-2001 June 21: Solar Radiation.....................................................30 

Figure A21. Thompson Tower-2001 June 21: Delta-T .................................................................31 

Figure A22. Thompson Tower-2001 June 22: Temperature .........................................................32 

Figure A23. Thompson Tower-2001 June 22: Relative Humidity ................................................32 

Figure A24. Thompson Tower-2001 June 22: Wind Speed ..........................................................33 

Figure A25. Thompson Tower-2001 June 22: Wind Direction.....................................................33 

Figure A26. Thompson Tower-2001 June 22: Pressure ................................................................34 

Figure A27. Thompson Tower-2001 June 22: Solar Radiation.....................................................34 
v 

Figure A28. Thompson Tower-2001 June 22: Delta-T .................................................................35 

Figure B1. Thompson Tower RAOB Launch-2001 June 19: Temperature...................................38 

Figure B2. Thompson Tower RAOB Launch -2001 June 19: Relative Humidity ........................38 

Figure B3. Thompson Tower RAOB Launch-2001 June 19: Wind Speed ...................................39 

Figure B4. Thompson Tower RAOB Launch-2001 June 19: Wind Direction..............................39 

Figure B5. Thompson Tower RAOB Launch-2001 June 19: Pressure .........................................40 

Figure B6. Thompson Tower RAOB Launch-2001 June 19: ELR ...............................................40 

Figure B7. Thompson Tower RAOB Launch-2001 June 20: Temperature...................................41 

Figure B8. Thompson Tower RAOB Launch-2001 June 20: Relative Humidity .........................41 

Figure B9. Thompson Tower RAOB Launch-2001 June 20: Wind Speed ...................................42 

Figure B10. Thompson Tower RAOB Launch-2001 June 20: Wind Direction............................42 

Figure B11. Thompson Tower RAOB Launch-2001 June 20: Pressure .......................................43 

Figure B12. Thompson Tower-2001 June 20: ELR.......................................................................43 

Figure B13. Thompson Tower RAOB Launch-2001 June 21: Temperature.................................44 

Figure B14. Thompson Tower RAOB Launch-2001 June 21: Relative Humidity .......................44 

Figure B15. Thompson Tower RAOB Launch-2001 June 21: Wind Speed .................................45 

Figure B16. Thompson Tower RAOB Launch-2001 June 21: Wind Direction............................45 

Figure B17. Thompson Tower RAOB Launch-2001 June 21: Pressure .......................................46 

Figure B18. Thompson Tower RAOB Launch-2001 June 21: ELR .............................................46 

Figure B19. Thompson Tower RAOB Launch-2001 June 22: Temperature.................................47 

Figure B20. Thompson Tower RAOB Launch-2001 June 22: Relative Humidity .......................47 

Figure B21. Thompson Tower RAOB Launch-2001 June 22: Wind Speed .................................48 

Figure B22. Thompson Tower RAOB Launch-2001 June 22: Wind Direction............................48 

Figure B23. Thompson Tower RAOB Launch-2001 June 22: Pressure .......................................49 

Figure B24. Thompson Tower RAOB Launch-2001 June 22: ELR .............................................49 
vi 

Preface 

In 2001, the U.S. Army Research Laboratory, Meteorological-sensors Integration Team, 

conducted a series of three field tests in the southwestern desert of the United States. The 

purpose was to identify, characterize, and exploit repeatable atmospheric patterns found in the 

lowest layer of the Boundary Layer, the Surface Layer. The repeatable pattern selected was the 

Surface Layer Stability Transition. Each field test was timed with the purpose of validating a 

seasonal extreme in the annual morning Stability Transition (ST) timing cycle. The seasonal 

minima, equated with the Equinox months, are documented in separate technical reports. This 

technical report focuses on the seasonal maximum point occurring in the Solstice month of June. 

Each field test serves as a building block in the overall goal of modeling the ST. The 

information gained from these field tests has three fundamental links to the U. S. Army and to 

the military in general: 

1. This research expands on U.S. Army Chief of Staff Shinseki’s vision. 

2. The knowledge of exploitable atmospheric characteristics, such as an ST, enhances electrooptical weapon effectiveness and efficiency. 

3. The accurate ST forecasts provide crucial initializing information for atmospheric models 

that forecast chemical and biological weapon effects, as well as transport and diffusion 

effects. 
vii 

Acknowledgements 

Appreciation is extended to the Meteorological-sensors Integration Team (MIT) members for 

their successful execution of the 2001 June Atmospheric Surface Layer Field Test. The MIT 

Team members included: Robert Brown, Edward Creegan, Doyle “Scott” Elliott, Alfred 

Gutierrez, David Quintis, Gail Vaucher (Team Leader) and Jimmy Yarbrough. Also, 

appreciation goes to Ms. Nancy Fudge, for her efforts in linking the remote site field test 

activities with the demands of the standard work hour routines. 
1 

Executive Summary 

U.S. Army Chief of Staff Shinseki stated that his U.S. Army vision was to see first, act first, and 

kill first. In GovExec.com’s Daily Briefing, Freedberg Jr. wrote that the most powerful, accurate 

and quickest weapon on the planet is the laser. Both military concerns have one major hurdle, 

“seeing” through the atmosphere. The Surface Layer Stability Transition (SLST) Research has 

been investigating naturally occurring atmospheric patterns that enhance or detract from the 

successful “seeing” mission. These same Stability Transition (ST) patterns also provide 

knowledge of when the effects of chemical and biological weapons will shift from foe (toxic 

concentrations in a limited area) to friendly (non-toxic concentrations in a broad area), and vice 

versa. Likewise, initializing the convective Boundary Layer growth phase (ST) impacts civilian 

and military Atmospheric Dispersion/Diffusion Model accuracy. For the military, knowing when 

a smoke screen will “clear”, for example, could prove to be a significant strategic advantage on a 

battlefield. 

In 2001, the Meteorological-sensors Integration Team conducted three field tests with the 

primary purpose of characterizing, modeling, and exploiting repeatable patterns in the lower 

portion of the Atmospheric Boundary Layer. The repeatable patterns investigated were the 

morning ST, or Neutral Events (NE). The 2001 June 20–22 dates were selected based on a 

forecasted maximum time interval between the local Sunrise and an Ideal ST case. Two other 

correlated field tests address the seasonal sunrise-to-NE time interval minima (March, 

September, 2001). These latter tests are documented separately. 

The SLST research pursued two measurement and analysis methods: Eulerian (Tower data) and 

quasi-Lagrangian (Rawinsonde data). The June 2001 results unexpectedly provided a healthy 

dataset for Non-ideal ST conditions. Within these three days were excellent examples of a predawn NE, extended NEs, and multiple NEs. The information documented here serves as a useful 

building block in support of their primary purpose. 
2 

1. Introduction 

This publication is the second of three technical reports documenting the 2001 Surface Layer ST 

Field Tests. Sections 1.1 and 1.2 are reproduced from the Surface Layer Stability Transition 

Research, Minimum Time Delay from Sunrise: 2001 March Case Study (Vaucher et al., 2003). 

1.1 U.S. Army Interest in Atmospheric Stability Transition Research 

Atmospheric Stability Transition (ST) Research links to military interests in at least three arenas. 

In the July 2002 Army Materiel Command Newsletter, U.S. Army Chief of Staff Shinseki stated 

that his vision for the U.S. Army was “to see first, act first, kill first...To see first, we must have 

persistent and pervasive intelligence-gathering capabilities” (Burlas, 2002). The atmosphere is 

one of the major hurdles retarding the efficiency of “seeing first.” The Boundary Layer 

Exploitation Task-Surface Layer Stability Transition (SLST) Research has been investigating 

naturally occurring atmospheric patterns that enhance or detract from the successful “seeing 

first” capability. Under favorable atmospheric conditions, target identification is potentially 

done quicker, making the last two actions of the Shinseki’s U.S. Army vision more efficient and 

effective. 

Sydney Freedberg Jr. wrote in his GovExec.com Daily Briefing, that the most powerful, most 

accurate and quickest weapon on the planet, the laser, has one major obstacle, the weather 

(Freedberg, 2001). To quantify the atmospheric impact on this, or any other electro-optical (EO) 

weapon, one needs to understand a parameter called “seeing”. To an astronomer, “seeing” is the 

arc second or angle occupied by the star image at the full-width and half-maximum of its 

intensity profile, as viewed from a specific point in the atmosphere (Businger et al., 2002). 

“Seeing” improves or degrades with changes in the atmospheric optical turbulence strength and 

location as quantified by profiles of the refractive index structure function Cn

2

. The SLST 

Research grew out of EO propagation research, and now serves as a building block for 

understanding and forecasting the naturally occurring atmospheric cycles that are both favorable 

and non-favorable for the laser and any subset of this weapon type. 

Finally, a significant urban warfare hazard is the release of chemical and biological weapons. 

The atmosphere, specifically the Boundary Layer convection, can enhance or detract from the 

weapon’s effectiveness. From a military perspective, knowledge of a ST means knowledge of 

when the chemical and biological weapon’s effect will shift from foe (toxic concentrations in a 

limited area) to friendly (non-toxic concentrations in a broad area), and vice versa (Angevine et 

al., 2001). 

Likewise, initializing the convective Boundary Layer growth phase (the ST) is a primary interest 

to civilian and military Convective Boundary Layer and Atmospheric Dispersion/Diffusion 
3 

Modelers. Model results often reflect the initial input accuracy. For the military, knowing when 

a smoke screen will “clear”, for example, could prove to be a significant strategic advantage on a 

battlefield. Thus, the ST pattern ties to both military and civilian applications (Angevine et al., 

2001). Additional civilian interests will be described in the next section. 

1.2 Civilian Interest in Atmospheric Stability Transition Research 

The Atmospheric Boundary Layer behavior during the period between the fully developed 

convection of mid-day and the stable conditions of the nocturnal Boundary Layer is poorly 

understood, but is of interest in several fields, including chemical and pollutant modeling 

(Grimsdell and Angevine, 2002). Grimsdell and Angevine focused their work on the afternoon 

ST in agricultural environments. However, their assessment regarding the poor understanding is 

also true for the morning Surface Layer ST in a desert environment. 

Finally, in the June 2002 Bulletin of the American Meteorological Society, Businger et al., 

describe the unique weather forecasting requirements for the highly technical stellar viewing at 

Hawaii’s Mauna Kea Observatories. Clear air turbulence in both the free atmosphere and in the 

Boundary Layer were flagged as causes for image distortion and blurring for their ground-based 

telescopes. Forecasting the observing quality for seeing parameters accurately is a key factor in 

the successful scheduling of these very expensive civilian optical and infrared instruments. 

Knowing when the atmospheric impact would be minimal, such as during a ST, would be a 

significant improvement and enhancement for the astronomical community (Businger et al., 

2002). 

1.3 Purpose and Overview 

The purpose of this report is to document the results and new understanding gleaned from the 

2001 June Solstice-Atmospheric Surface Layer Field Test, conducted by the U.S. Army 

Research Laboratory (ARL), Meteorological-sensors Integration Team (MIT). This test was 

executed at Thompson Tower (Lat: 32.35, Long: -106.47), White Sands Missile Range (WSMR), 

NM. The overriding mission of this second of three fiscal year 2001 (FY01) field tests, was to 

validate the proposed Seasonal Algorithm used in forecasting the exact time of the morning ST. 

This goal stemmed from a larger Atmospheric Boundary Layer investigation: to characterize and 

exploit the repeatable patterns found within the lower portion of the desert Atmospheric 

Boundary Layer (Surface Layer). A routine mechanism for describing the Surface Layer is 

turbulence (Tatarski, 1961). Turbulence directly impacts the stability of the Surface Layer, 

which in turn affects the U.S. Army’s ability to function efficiently. Thus, the research results 

feed both the scientific goals of better understanding the Atmospheric Boundary Layer 

dynamics, and the U.S. Army’s need to improve their efficiency while working in the Surface 

Layer. 
4 

1.4 Background of the Stability Transition Study 

The following historical review of the ST study is reproduced from the Surface Layer Stability 

Transition Research, Minimum Time Delay from Sunrise: 2001 March Case Study (Vaucher et 

al., 2003). 

The initial ST study was funded by the Atmospheric Science Laboratory and conducted at the 

U.S. Army-owned High Energy Laser Systems Test Facility (HELSTF), NM in the mid-1990s 

(USASL Contract). This study was prompted by an operational need to minimize the impact of 

atmospheric optical turbulence (AOT) on the High Energy Laser (HEL) when propagating along 

a 1 km path. Based on observations, the HELSTF meteorologists noted that twice a day the 

AOT would drop to a minimum. These AOT minima correlated closely with the morning and 

evening STs. 

Over time, ARL meteorological operational researchers developed a “rule of thumb” approach 

for forecasting the morning and evening STs. This “rule of thumb” suggested that a minimum 

amount of AOT occurred when the atmosphere was neither stable, nor unstable, and that such a 

“Neutral Event (NE)” occurred 60 min after sunrise, and 40 min before sunset. While the “rule 

of thumb” was able to yield a ballpark accuracy, the high cost of HEL testing quickly demanded 

a more precise forecast. Thus, a more rigorous investigation began. 

In 1994, Vaucher and Endlich published results from the first of two significant studies. 

According to their 2-month study, the average occurrence of the morning NE was about 70 min 

after sunrise. The time difference between sunrise and the associated NE ranged between 40 and 

133 min after sunrise. The evening NE occurred an average of about 60 min before sunset, with 

a Sunset-NE time difference ranging between 98 and 12 min before sunset (Vaucher and 

Endlich, 1994). They also noted that there was an implied trend in their statistical findings. 

Consequently, a follow-on study was pursued. 

In 1995, Vaucher and Endlich published the results from a 16-month AOT NE study conducted 

at HELSTF, NM. Recognizing the local heat flux as the primary contributor to AOT, the authors 

isolated three variables (Sunrise/Sunset time, Delta-T and Insolation) related to the heat flux, and 

observed their relationship to the NE over a 1 km desert path. The 16 m minus 2 m Temperature 

(T) difference (Delta-T) was examined at the start and end of the sampling path. Results 

reported near-surface, slightly dry adiabatic conditions present during a NE. The NE-insolation 

values showed that the ranges of insolation magnitudes at the Sunrise-NE were about twice those 

sampled at the Sunset-NE. This observation was explained as a function of the sun’s elevation. 

The most significant discovery of the 1995 study, with respect to ST forecasting, came while 

overlaying local sunrise and NE times. The minimum average time difference between local 

sunrise and NE was reported in the Equinox months. The maximum monthly time difference 

average occurred in the Solstice months. Vaucher and Endlich theorized that the skewed diurnal 

heating-cooling cycle of the solstice periods generated strong near-surface temperature 
5 

inversions that delayed the transition into the near-dry adiabatic atmosphere required for a NE. 

During the Equinox, the 24-h heating-cooling cycle was nearly equal. Therefore, minimal time 

was needed for the day or nighttime atmosphere to transition into the near-dry adiabatic 

environment (Vaucher and Endlich, 1995). 

Figure 1 displays the seasonal effect discovered by Vaucher and Endlich. In this figure, the 

Sunrise NE (SRNE) Rule of Thumb Forecast is contrasted with the actually observed NE time. 

Figure 1. Local Sunrise, SRNE Rule of Thumb, and NE Times, 1994 February-1995 

June (Raw Data). 

To display the oscillation more plainly, figure 2 shows the “rule of thumb”, the monthly 

averaged NE time, and the actual NEs. 

Figure 2. SRNE Rule of Thumb, Raw and Monthly Averaged NEs, 1994 February-1995 June. 
6 

Removing the actual data, figure 3 shows the annual cycle of average NE by month. Note he 

Equinox NE minima (September, March) and the Solstice NE maxima (June, December). The 

first minimum is ignored due to the lack of data for the initial month. 

Figure 3. Monthly Averaged Sunrise Neutral Event Time Differences, 1994 April-1995 June. 

Based on the 16-month study, Vaucher and Endlich updated the Rule of Thumb NE Forecast 

approach by introducing a seasonal correction curve. The coefficients produced by the Fourier 

Waveform Analysis can be found in their 1995 Battlefield Atmospheric Conference paper 

(Vaucher and Endlich, 1995). 

The 16-month study left some unanswered questions: 

1. Are the updated Rule of Thumb NE Forecast algorithms site specific? What about a nondesert environment? What about other latitudes? 

2. Is the seasonal oscillation real or a coincidence? 

3. The current model works under Ideal atmospheric conditions. What about under Non-ideal 

conditions (see section 1.6)? 

ARL addressed some of these questions during the FY01 field tests. First, however, this report 

examines the ST character and the Ideal versus Non-ideal atmospheric conditions.

1.5 Character of the Stability Transition 

The ST character is best understood by examining a full 24-h stability cycle. Figure 4 presents a 

“typical” diurnal (a March Equinox AOT time series over a high elevation desert site in the 

southwestern United States) and can be used as a visualization tool for the following stability 

cycle description. Additional information on typical stability cycles can be found in 

Meteorology for Scientists and Engineers (Stull, 2000) and An Introduction to Boundary Layer 

Meteorology (Stull, 2001). 
7 

1E- 19

1E- 18

1E- 17

1E- 16

1E- 15

1E- 14

1E- 13

1E- 12

1E- 11

1E- 10

0 3 6 9 12 15 18 2 1 2 4

Local Time (Dec Hr - MST)

Cn

2 (m-2/3)

Cn2 : 1km, 8 m AGL

S unrise ( 6 .0 7 MS T)

S unse t ( 18 .3 3 MS T)

 

0

5

10

15

20

25

0 3 6 9 12 15 18 21 24

Local Time (Dec Hr - MST)

Temperature (C)

Tem perat ure (2 m)

Tem perat ure (1 6m )

Sunrise (6.07 MST)

Sunset (1 8.33 MST)

0

200

400

600

800

1000

1200

0 3 6 9 12 15 18 21 24

Local Time (Dec Hr - MST)

Insolation (W/m2

)

Insolation

Sunrise (6.07 MS T)

Sunset (18.33 MST)

Figure 4. Coincident Cn

2

, Temperatures, and Insolation Time Series 

along a 1–km path for 24 March 2001 at HELSTF, NM. 

0000-Sunrise. Under clear skies, calm winds, and low ground moisture, the desert basin at 0000 

hours Local Time is stably stratified. The coldest temperatures are at the lowest levels (Delta-T 

> 0). The heat flux is negative, and the AOT is a moderate-to-low level. Katabatic flow off 

neighboring mountains serves as a catalyst for overturning and mixing the nighttime stable 

atmospheric layers. The result is a mélange of density variations, which produces intermittent 

maxima of AOT. If winds decrease, AOT will return to the normal moderate-to-low level. 

Sunrise occurs. The rays of sunrise start warming the ground, which radiates heat into the lowest 

atmospheric layer. The heat flux steadily increases, causing the stable atmosphere to become 

isothermal and “neutral.” Cn

2

, coincidently, drops to a minimum. This is the morning, or 

Sunrise AOT NE. 
8 

Daytime. As the sun continues warming the ground throughout the morning, the neutral stability 

shifts into an unstable state. The heat flux is positive. The vertical temperature differences are 

now negative and Cn

2

 increases. Atmospheric convection attempts to rebalance the unstable 

conditions by mixing the near surface warm air into the cooler air aloft. The persistent sun 

strengthens the unstable state, deepening the mixed layer. The constant mixing intensifies the 

atmospheric density variations and the AOT further increases. AOT reaches a peak around 

midday, or soon after. 

The waning of the sun in the clear afternoon skies reduces the insolation and decreases the 

negative Delta-T magnitudes. Subsequently, AOT decreases. Just prior to sunset, the 

atmosphere briefly becomes near-dry adiabatic (neutral) and Cn

2 drops to a minimum. The heat 

flux goes to zero and the day’s second NE takes place. 

Sunset occurs. Civil, Military and Astronomical Twilights quickly evolve until there is the 

nighttime darkness. The previously warmed soil strongly emits the Solar Radiation absorbed 

during the daylight hours and cools rapidly. Delta-T becomes positive, confirming the presence 

of a stable atmosphere. Colder, heavier air, from the surrounding mountains and hills, drains 

into the valleys, serving as a mixing tool. The non-uniform radiative cooling and clear sky 

drainage flow creates an ambient mixing, which keeps the AOT at a moderate level throughout 

the night. The moderate AOT is punctuated by occasional, intermittent AOT maxima. 

Within the diurnal cycle just described, the two primary NE times are clearly linked with the 

local sunrise and sunset. As the stable nighttime conditions transition to unstable daytime 

conditions, a Sunrise NE occurs. Likewise, as the unstable daytime evolves to a stable nighttime 

atmosphere, a Sunset NE occurs. Common to both scenarios is a period in which the atmosphere 

is near-dry adiabatic, exhibiting the least variations of Cn

2 along a horizontal and vertical path. 

The target of the SLST research is to successfully forecast the initial time for these transition 

events (Vaucher et al., 2003). 

1.6 Ideal and Non-ideal Stability Transition Forecast Standards 

Two distinct scenarios, Ideal and Non-ideal atmospheric conditions, were observed during the 

mid-1990 ST studies: 

1. Ideal atmospheric conditions were defined as clear skies, low winds and low ground 

moisture. 

2. Non-ideal atmospheric conditions included all other atmospheric traits, especially any 

cloud occultation of the sun during sunrise/sunset. 

Local atmospheric conditions determined the ST duration. Under Ideal conditions, the transition 

was often less than 2 min. Ironically, the Ideal condition ST forecast (with seasonal correction 

algorithms) produced the best results for the HELSTF, WSMR, NM site. In fact, one could 

accurately forecast to the minute when a Sunrise NE would occur 9 months in advance of the 

forecast, presuming that the day of validation had Ideal atmospheric conditions. 
9 

Forecasting for the Non-ideal atmospheric scenario was another story. First, the NE duration 

was anywhere from 1 min to over 20 min. In this technical report, the 2001 June SolsticeAtmospheric Surface Layer Test data will show an atmospheric transition state being sustained 

for at least 26 min. Another characteristic of Non-ideal scenarios was the generation of multiple 

NEs. Some major contributors to these Non-ideal NE conditions included: 

1. Solar disc occultation during sunrise/sunset. 

2. Sun ray obscuration after sunrise/before sunset. 

3. The presence of local ground moisture. 

4. The presence of non-standard local forcing (such as a frontal passage). 

2. Seasonal Algorithm Statistical Maximum Test 

In section 1.4, “Background of the Stability Transition Study,” figure 3 showed the statistical 

maximum in the seasonal algorithm to be in the Solstice month of June. Climatologically, June 

in New Mexico is hot, dry, and dominated by clear skies. The probability for accomplishing our 

desired objective was high. 

2.1 2001 June Solstice-Atmospheric Surface Layer Test Overview 

The 2001 June Solstice-Atmospheric Surface Layer Test was executed in two phases: a Pre-Test 

was conducted 5–7 and 19 June; and the actual Test occurred 20–22 June. The test site used was 

the 100 ft Thompson Tower site at WSMR, NM, with a scintillometer path extending about 1 km 

west-southwest to the Ammo Site. Participants of the Test included the members of the MIT, 

Dave Tofsted of ARL’s Weather Exploitation Branch and Carlos Marrerro (a visiting student). 

The Test Coordinator was Gail Vaucher. The purposes of the Test, with their point-of-contacts 

(POC), were: 

1. To be the second of three FY01 sampling sets aimed at verifying the maximum and 

minimum magnitudes of the Neutral Event Forecasting Model seasonal effects (POC: Gail 

Vaucher). 

2. To quantitatively characterize the desert Atmospheric Surface Layer by studying the 

atmospheric lapse rate changes (stability), wind currents, and insolation during the nightto-day transition period (POC: Doyle “Scott” Elliott). 

3. To characterize atmospheric transition events aloft via the Wind Profiling Radar (POC: 

Edward Creegan). 
10 

Prior to the field test execution, two 4 m scintillometer towers (Thompson Tower and Ammo 

Site) were re-leveled and secured for use, and cabling was repaired (local wildlife had damaged 

existing cables). The temporary housing for the computer equipment at the remote Ammo Site 

was provided by a Commercial Utility Cargo Vehicle with shelter. The power for the site was a 

mobile 20 kW generator. A mobile High Speed Trailer (HST) attached to hard power provided 

the equivalent for the Thompson Tower site. The versatile HST served as a Post-test data 

processing center and Testers’ Conference Room. 

Meteorological sensors included a 4 m TacMet II Unit at Ammo Site, and two surface sensor 

units linked by a Campbell Data Logger at Thompson Tower. Sensors on Thompson Tower 

were mounted at 2 m, 5 m, 38 m, and 39 m levels. Vaisala global positioning system (GPS) 

rawinsondes were launched from a High Mobility Multi-Wheeled Vehicle (HMMWV) situated 

west of Thompson Tower. The HMMWV also served as the housing for the 924 MHz Wind 

Profiling Radar. The Wind Profiling Radar Antenna was placed west of Thompson Tower and 

slightly southwest of the HMMWV. A 25 kW Quiet Generator powered the HMMWV. The 

HST was placed north and slightly west of Thompson Tower. A Field Test Structures and 

Sensors Layout diagram was documented in the Test Logbook. 

During the Pre-Test check of equipment and acquisition capabilities, the tower meteorological 

sensors, radar, RAOB and scintillometer systems ran simultaneously. Errors were noted and 

solutions ultimately found for the RAOB and Radar systems. Scintillometer alignment was 

successful. The scintillometer software was in an experimental testing mode; therefore, the PreTest Cn

2

 results were inconclusive. The rest of the Thompson Tower and Ammo Site Pre-test 

data were deemed acceptable. 

2.2 Test Execution 

Test Days 1–3 (2001 June 20–22) began at 0400 Mountain Daylight Time (MDT), with all 

participants traveling to the 100 ft Thompson Tower in a caravan. This strategy served to 

minimize desert dust around the field site. There were three data acquisition Sub-cases 

scheduled per day. These Sub-cases characterized the nighttime desert atmosphere (0430–0700 

MDT), the onsite atmospheric NE (0700–0900 MDT), and the daytime desert atmosphere (0900–

1100 MDT). A morning WSMR mission forced Test Day 2, Sub-cases 2 and 3 RAOBs to 

originate from a WSMR C-station RAOB launch location. All other RAOB launches were 

conducted at the Thompson Tower site; all Sub-case runs were uninterrupted. 

2.3 Test Summary 

This section begins with a brief characterization of the nighttime (stable), transition (NE), and 

daytime (unstable) Sub-cases. Section 2.3.2 describes the unique features of the three NEs 

observed during the June Test. The information presented in that section is based on the plots 

generated during execution of the Test. Additional details will be discussed in section 3 

(Vaucher, 2001). 
11 

2.3.1 Characterization of Nighttime, Transition, Daytime Atmospheric Conditions 

This section presents data from Days 1 and 2 only. Day 3 was excluded due to the complicating 

factors of a backdoor front stimulating some relatively rare, early morning thunderstorm activity 

east of the site. Day 3, the final test day, will be addressed later in this study. 

General Synoptic Weather Information. An atypical (seasonally early) monsoon-type pattern 

over WSMR brought in a southeast flow of tropical moisture from the Gulf of Mexico. The 

abnormally high daytime dewpoint temperatures gave the area nearly an inch of Precipitable 

Water, resulting in the constant threat of afternoon thunderstorms (Forecast for White Sands 

Missile Range, Intellicast.com, Real-Time Weather Data, 2001). 

Nighttime (0430–0700 MDT). Pressure (P) increased slightly (about +1 mb/Sub-case time 

duration) as the dawn hours approached. Cool temperatures were sampled near the surface, 

generating a Delta-T of +3 to +6 oC. Relative Humidity (RH) was significantly greater at 2 m 

than at 38 m. Winds were less than 5 m/s, with generally divergent magnitudes between the 5 m 

and 39 m sampling heights. Consequently, wind directions (WD) were also divergent, though 

often from the same gross northern quadrants. All test days reported clouds obscuring the stars, 

mainly along the eastern horizon. 

Transition (0700–0900 MDT). The P continued to increase with time (about +0.7 mb/Sub-case 

time). Delta-T began with a stable +3 oC (T2m < T38m). After the transition/NE, Delta-T was 

approximately 2 oC (unstable). The greatest Delta-T rate of change was observed between 0724 

and 0815 MDT. The RH began with a difference of 20% (greatest RH at 2 m). Then, like T, RH 

also transitioned, so that the greatest RH was at the higher level. The post-transition RH 

difference was less than 5% (dryer conditions generally at 2 m). Wind speeds (WS) between the 

5 m and 39 m levels were less than 5 m/s. While the two levels began as pseudo-independent 

airflow, the magnitudes appeared to converge at the time of transition. This unified condition 

persisted throughout the end of this case. Solar Radiation (SR) showed the greatest rate of 

increase over this time period. Evidence of intermittent cloud cover was validated with the 

independently sampled observations that are in the Test Logbook. 

Daytime (0900–1100 MDT). The smallest P change occurred during this Sub-case time period (–

0.20 and +0.01 mb/Sub-case time). The Delta-T consistently hovered around –2 o

C (unstable), 

with the warmest T at 2 m. The RH differences (2 m and 38 m) were less than 5%. The WS 

was < 5 m/s, with both tower levels reporting a relatively unified direction. The SR showed a 

slower rate of increase. Cloud obscuration was less over this time period. 

2.3.2 Unique Neutral Events 

All 3 days began with partly cloudy skies that evolved into isolated thunderstorms by evening. 

This pseudo-monsoon pattern consistently delayed the local sunrise. The UNOBSTRUCTED 

sunrise for this latitude and these dates would have been 0559 MDT (Day 1) and 0600 MDT 

(Days 2 and 3). 
12 

Day 1(20 June). Cirrus clouds delayed sunrise 6 min. Between sunrise and NE, there were two 

periods in which cirrus clouds fully obscured the sun. The consequences of the irregular surface 

heating manifested in a 27-min delay from the Ideal Conditions-NE Forecast time. The morning 

transition was a single event for this Test Day. 

Day 2(21 June). Sunrise was delayed 9 min due to mid-level clouds along the eastern horizon 

(residue of early morning cumulonimbus). Intermittent occulting of the rising sun was coupled 

with the effects of a significant increase in local ground moisture from the overnight 

thunderstorms. The resulting delay in the Ideal Conditions-NE was about 49 min. The morning 

transition was a single event for Test Day 2. 

Day 3(22 June). Day 3 presented the most fascinating data of the Test. This data set began in a 

nighttime NE. Without a calibrated scintillometer or imager to instantaneously validate the NE, 

the NE definition had to be subdivided into two empirically derived Delta-T threshold gradients: 

+/–0.25 and +/–0.09. Using the grosser threshold, the length of the in-progress NE was 26 min. 

The finer thresholds sampled a 4-min NE. One proposed explanation for the nighttime-NE was 

that the cool outflow of a local, active thunderstorm generated the extended, pre-dawn NE 

conditions. 

Sunrise for Day 3 was delayed 31 min by the decaying anvil (cumulonimbus) occulting the solar 

disc. The abundance of cloud cover prohibited the normal steady increase in surface heating, 

resulting in three daylight-NE/STs. Using gross thresholds, these lasted 4, 10, and 3 minutes. 

Strangely, the first 4-min transition status overlapped the NE time forecasted for Ideal 

conditions. The final transition occurred once the solar disc had cleared the thickest of the 

altocumulus cloud cover. The time of the final transition was approximately 61 min after the 

Ideal NE forecast time. 

3. Discussion of Results 

Test Day 3 provided the most unusual results and is elaborated in this section. Previous 

observations have identified at least two unique NE characteristics under Non-ideal atmospheric 

conditions: Extended and Multiple STs. At the time of publication, the authors were not aware 

of any study that had documented the variety of ST durations. Since Extended and Multiple NE 

conditions present favorable opportunities to military interests, knowing the duration of these 

opportunities (even if approximately) becomes important. Understanding the prompting for 

these conditions is an interest of the academic community, since these observations further 

characterize the Surface Layer dynamics. 
13 

3.1 Extended Stability Transitions 

Extended STs are normally associated with overcast, windy days. In contrast, the first extended 

NE of this test began at night. The very first Thompson Tower data sampled (0421 MDT) from 

Day 3 abruptly informed us that neutral conditions were already in progress. The 0435 MDT 

meteorological observations described the sky as “0.5 cirrus, no twilight visible, CB and 

lightning observed to the northeast” (Test Logbook, 2001). Surface winds were about 3 m/s 

from the north-northeast. Twenty-six minutes into our data acquisition, the nighttime NE 

silently eased into the more typical stable Surface Layer status. By 0450 MDT, the local Surface 

Layer observations reported “0.3 thin cirrus, less than 0.1 altocumulus, twilight on the eastern 

horizon and no lightning” (Test Logbook, 2001). These cloud conditions persisted for the next 

half hour with only the pre-dawn light increasing. As mentioned earlier, empirical analysis has 

tagged the non-threatening outflow of the active thunderstorm northeast of the Test Site as being 

the catalyst for this unexpected atmospheric condition. 

Observations at local sunrise (0600 MDT) stated that the solar disc was obscured by cirrus, pink 

clouds (altocumulus/cirrus) to the south, no stars were visible, only a planet was visible, and an 

anti-twilight arc was beginning to form. Within 15 min, the planet was no longer visible. The 

sunrays were slipping through random slits in the cloud deck, illuminating the very tops of the 

western mountain peaks. Not until 0631 MDT did the solar disc finally clear the horizon clouds. 

Surface winds were less than 5 m/s and had shifted to the south, southeastern quadrants. 

Unfortunately, the sun’s unobstructed path did not persist. 

3.2 Multiple Stability Transitions 

On Test Day 3, the first of the multiple STs occurred within the Ideal NE forecasted time (0711 

MDT) plus/minus one standard deviation. No observations were taken at the start of the 

extended post-dawn NE (0708–0711 MDT). However, the 0710 MDT observation reported “0.3 

AC, 0.1 cirrus, sun blocked by thick AC” (Test Logbook, 2001). The local atmosphere briefly 

returned to a stable state before the next NE. 

The second of the three transitions (0716–0725 MDT) was also an extended NE. No significant 

atmospheric changes were observed from the initial transition. Clouds continued to occult the 

sun. Following this 10-min event, the local atmosphere, again, returned to the stable condition. 

Altocumulus cloud cover increased over the subsequent 42 min. 

By the last of the multiple transitions (0812–0814 MDT), observations were “0.9 AC, 0.1 cirrus 

with clearing to the south” (Test Logbook, 2001). Surface winds were around 3.7 m/s out of the 

south. A healthy, persistent daytime unstable atmosphere followed this last NE. 
14 

4. Conclusion 

Expect the unexpected. The atmospheric conditions anticipated for this June Test were clear 

skies, high desert temperatures, and very dry. In other words, Ideal conditions for validating the 

NE Forecasting Model. The actual Test’s atmosphere was a 2-week, early monsoon pattern: 

cloudy skies, moderately high temperatures, moist ground, early morning thunderstorms, and 

even the threat of a gust-nado sighted to our west. While this atypical weather pattern 

challenged the ongoing validation of the NE Forecasting Model, it also provided excellent 

evidence (documentation) of nighttime NEs, extended NEs, and the occurrence of multiple 

daytime NEs. The mission of this second of three field tests was to identify, characterize, model, 

and exploit repeatable patterns within the Atmospheric Surface Layer that are useful to the 

military. After reviewing the results of the Test, it is the authors’ opinion that this Test gained an 

unexpected significance in that it provided quantitative evidence that even under “bad” or Nonideal weather conditions, the atmospheric surface layer has exploitable military value (i.e., NEs) 

for those who have the eyes to see this benefit. 
15 

Acronyms 

AGL Above Ground Level 

AOT Atmospheric Optical Turbulence 

ARL U.S. Army Research Laboratory 

Cn

2

 Index of Refraction Structure Function 

Delta-T Temperature Difference [T38m – T2m] 

ELR Environmental Lapse Rate 

EO Electro-Optical 

GPS Global Positioning System 

HEL High Energy Laser 

HELSTF High Energy Laser Systems Test Facility 

HMMWV High Mobility Multi-wheeled Vehicle 

HST High Speed Trailer 

MIT Meteorological-sensors Integration Team 

MDT Mountain Daylight Time 

NE Neutral Event 

P Pressure 

POC Point of Contact 

RAOB Rawinsonde Observation System 

RH Relative Humidity 

SLST Surface Layer Stability Transition 

SR Solar Radiation 

SRNE Sunrise Neutral Event 

ST Stability Transition 

T Temperature 

WS Wind Speed 

WSMR White Sands Missile Range 

WD Wind Direction 
16 

References 

Angevine, Wayne M.; Baltink, H.K.; Bosveld, Fred. Observations of the Morning Transition of 

the Convective Boundary Layer. Boundary Layer Meteorology, 2001 (April 6). 

Burlas, Joe. Army Prophet Debuts on Capitol Hill. The Command Post Newsletter; Army 

Materiel Command, Army News Service: July 2002. 

Businger, S.; McLaren, R.; Ogasawara, R.; Simons, D.; Wainscoat, R. Starcasting. BAMS 2002, 

83 (6), 858–871. 

Freedberg, Sydney J. Jr. Flash! Zap! Boom! Lasers come of age. National Journal, April 23, 

2001. 

Grimsdell, A.W.; Angevine, W.M. Observations of the Afternoon Transition of the Convective 

Boundary Layer. Journal of Applied Meteorology, 2002 (January), 3–11. 

Stull, Roland; An Introduction to Boundary Layer Meteorology; Kluwer Academic Publishers: 

Norwell, MA, 1988. 

Stull, Roland; Meteorology for Scientists and Engineers; 2nd Ed; Brooks/Cole Thompson 

Learning: Pacific Grove, CA. 2000; Chapters 1–6. 

Tartarski, V.I. Wave Propagation in a Turbulent Medium; Dover Publications, Inc.: New York; p 

1961. 

Test Logbook; 2001 June Solstice-Atmosphere SL Test; U.S. Army Research Lab; WSMR, NM, 

2001. 

U.S. Army Atmospheric Sciences Laboratory; Contract No: DAAD07-89-C-0035; Task No: 

9015 and 9101. 

Vaucher, Gail-Tirrell. 2001 March Equinox-Atmospheric Surface Layer Test, Test Summary, 

White Sands Missile Range, NM. Internal ARL Document, 2001. 

Vaucher, Gail-Tirrell; Bustillos, M.; Gutierrez, A. Surface Layer Stability Transition Research, 

Minimum Time Delay from Sunrise: 2001 March Case Study; Technical Report No: ARLTR-2798, to be submitted for publication, 2003. 

Vaucher, Gail-Tirrell; Endlich, Robert. Forecasting Atmospheric Optical Turbulence Neutral 

Events-Part II. Proceedings of the 1995 Battlefield Atmospheric Conference, Army Research 

Lab, White Sands Missile Range, NM, Dec 5–7, 1995. 

Vaucher, Gail-Tirrell; Endlich, Robert. Forecasting/Modeling the Atmospheric Optical 

Turbulence Neutral Events over a Desert Environment, Proceedings of the 1994 Battlefield 
17 

Atmospheric Conference, Army Research Lab, White Sands Missile Range, NM, Nov 29-

Dec 1, 1994. 

Forecast for White Sands Missile Range. http://weather.wsmr.army.mil/public/fcst.txt (accessed 

June 2001) White Sands Meteorology Branch, WSMR Weather Support Center. 

Intellicast.com. http://www.intellicast.com (accessed June 2001). 

Real-Time Weather Data. http://www.rap.ucar.edu/weather (accessed June 2001) University 

Corp for Atmospheric Research. 
18 
19 

Appendix A: Thompson Tower Data 

This appendix is part of ARL-TR-2823, Surface Layer Stability Transition Research 

Maximum Time Delay from Sunrise/Non-Ideal Conditions: 2001 June Case Study, U.S. 

Army Research Laboratory, White Sands Missile Range, NM 88002-5501. 

A Eulerian (fixed point) perspective on the atmospheric conditions during the Nighttime (Stable) 

to Daytime (Unstable) transition was quantitatively recorded by the Thompson Tower timeseries data. Thermodynamic data sampling was executed at 2 m and 38 m above ground level 

(AGL). Wind data was acquired at 5 m and 39 m AGL. For convenience, the data representing 

the lower layer is designated with a brown box and the upper layer with a blue open circle. 

Efficiency has dictated that all three Sub-cases (Stable, Neutral, Unstable) be presented in a 

single time-series plot. Approximate times for each Sub-case were: 

 Stable 0500–0600 MDT 

 Neutral 0630–0730 MDT 

 Unstable 0800–0830 MDT 

The 2001 June 19 Pre-Test data were included for completeness. The following are the four 

sections of Appendix A: 

• Figures A1–A7: 2001 June 19 

• Figures A8–A14: 2001 June 20 

• Figures A15–A21: 2001 June 21 

• Figures A22–A28: 2001 June 22 
20 

Figures A1–A7: 2001 June 19-Thompson Tower Data 

25

30

35

40

9 10 11 12 13

Local Time (Dec Hrs)

Temperature (C)

Temp [2m]

Temp [38m]

0

10

20

30

40

50

60

70

80

90

100

9 10 11 12 13

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]

RH [38m]

Figure A2. Thompson Tower-2001 June 19: Relative Humidity.

Figure A1. Thompson Tower-2001 June 19: Temperature.
21 

0

90

180

270

360

9 10 11 12 13

Local Time (Dec Hrs)

Wind Direction (deg)

WD [2m]

WD [39m]

Figure A3. Thompson Tower-2001 June 19: Wind Speed.

Figure A4. Thompson Tower-2001 June 19: Wind Direction.

0

1

2

3

4

5

6

7

8

9 10 11 12 13

Local Time (Dec Hrs)

W ind Speed (m/s)

WS [2m]

WS [39m]
22 

0

100

200

300

400

500

600

700

800

900

1000

9 10 11 12 13

Local Time (Dec Hrs)

Solar Radiation (W /m^2)

SR

875.5

876.5

877.5

878.5

879.5

9 10 11 12 13

Local Time ( Dec Hrs)

Pressure (mb)

P [33m]

Figure A6. Thompson Tower-2001 June 19: Solar Radiation.

Figure A5. Thompson Tower-2001 June 19: Pressure.
23 

-4

-3

-2

-1

0

1

2

3

4

9 10 11 12 13

Local Time (Dec Hrs)

Delta-Temperature (K)

Delta-T [2m-38m]

Zero Line

Figure A7. Thompson Tower-2001 June 19: Delta-T.
24 

Figures A8–A14: 2001 June 20-Thompson Tower Data 

0

10

20

30

40

50

60

70

80

90

100

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]

RH [38m]

16

21

26

31

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Temperature (C)

Temp [2m]

Temp [38m]

Figure A9. Thompson Tower-2001 June 20: Relative Humidity.

Figure A8. Thompson Tower-2001 June 20: Temperature.
25 

-180

-90

0

90

180

4 5 6 7 8 9 10 11

Loc al Time ( Dec Hrs)

Wind Direction (deg) 

WD [2m ]

WD [39m ]

Zero Line

0

1

2

3

4

5

6

7

8

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Wind Speed (m/s)

W S [2m ]

W D [39m ]

Figure A10. Thompson Tower-2001 June 20: Wind Speed.

Figure A11. Thompson Tower-2001 June 20: Wind Direction.
26 

Figure A13. Thompson Tower-2001 June 20: Solar Radiation.

Figure A12. Thompson Tower-2001 June 20: Pressure.

879

880

881

882

883

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Pressure (mb)

P [33m]

0

100

200

300

400

500

600

700

800

900

1000

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Solar Radiation (W/m^2)

Sol Rad (W/m^2)
27 

-8

-6

-4

-2

0

2

4

6

8

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Delta-Temperature (K)

Delta-T [2m-38m ]

Zero Line

Figure A14. Thompson Tower-2001 June 20: Delta-T.
28 

Figures A15–A21: 2001 June 21-Thompson Tower Data 

0

10

20

30

40

50

60

70

80

90

100

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]

RH [38m]

16

21

26

31

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Temperature (C)

Temp [2m]

Temp [38m]

Figure A16. Thompson Tower-2001 June 21: Relative Humidity.

Figure A15. Thompson Tower-2001 June 21: Temperature.
29 

0

90

180

270

360

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

W ind Direction (deg)

WD [2m]

WD [39m]

0

1

2

3

4

5

6

7

8

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Wind Speed (m/s)

WS [2m]

WS [39m]

Figure A17. Thompson Tower-2001 June 21: Wind Speed.

Figure A18. Thompson Tower-2001 June 21: Wind Direction.
30 

0

100

200

300

400

500

600

700

800

900

1000

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Solar Radiation (W/m^2)

Sol Rad (W/m^2)

879

880

881

882

883

4 5 6 7 8 9 10 11

Local Time ( Dec H rs)

Pressure (mb)

P [33m]

Figure A20. Thompson Tower-2001 June 21: Solar Radiation.

Figure A19. Thompson Tower-2001 June 21: Pressure.
31 

-8

-6

-4

-2

0

2

4

6

8

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Delta-Temperature (K)

Delta-T [2m-38m]

Zero Line

Figure A21. Thompson Tower-2001 June 21: Delta-T.
32 

Figures A22–A28: 2001 June 22-Thompson Tower Data 

0

10

20

30

40

50

60

70

80

90

100

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]

RH [38m]

0

5

10

15

20

25

30

35

4 5 6 7 8 9 10 11

Loca Time (Dec Hrs)

Temperature (C) 

Temp [2m]

Temp [38m]

Figure A23. Thompson Tower-2001 June 22: Relative Humidity.

Figure A22. Thompson Tower-2001 June 22: Temperature.
33 

0

90

180

270

360

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Wind Direction (deg) 

WD [2m]

WD [39m]

0

1

2

3

4

5

6

7

8

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Wind Speed (m/s)

WS [2m]

WS [39m]

Figure A24. Thompson Tower-2001 June 22: Wind Speed.

Figure A25. Thompson Tower-2001 June 22: Wind Direction.
34 

0

100

200

300

400

500

600

700

800

900

1000

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Solar Radiation (W /m^2)

Sol Rad (W /m^2)

Figure A27. Thompson Tower-2001 June 22: Solar Radiation.

Figure A26. Thompson Tower-2001 June 22: Pressure.

880

881

882

883

884

4 5 6 7 8 9 10 11

L o cal Time (D ec Hrs)

Pressure (mb)

P [33m]
35 

Figure A28. Thompson Tower-2001 June 22: Delta-T.

-4

-3

-2

-1

0

1

2

3

4

4 5 6 7 8 9 10 11

Local Time (Dec Hrs)

Delta-Temperature (k)

Delta-T (C)

Zero Line
36 
37 

Appendix B: Rawinsonde Data 

This appendix is part of ARL-TR-2823, Surface Layer Stability Transition Research 

Maximum Time Delay from Sunrise/Non-Ideal Conditions: 2001 June Case Study, U.S. 

Army Research Laboratory, White Sands Missile Range, NM 88002-5501. 

A Lagrangian (following the parcel) perspective on the atmospheric conditions during the 

Nighttime (Stable) to Daytime (Unstable) transition was quantitatively recorded by the 

Thompson Site rawinsonde (RAOB) data. RAOB data referenced as ‘C-station’ were released at 

the White Sands Missile Range C-station launch site (within 5 miles of Thompson Tower). A 

full day’s worth of data is presented on a single plot. The earliest Sub-case (Stable) is designated 

with a red solid box; an orange open circle shows the Neutral Sub-case; the Unstable Sub-case is 

a green solid triangle and any additional Unstable data is a blue open diamond. As a reminder, 

the general times designated for each Sub-case were: 

 Stable 0500–0600 MDT 

 Neutral 0630–0730 MDT 

 Unstable 0800–0830 MDT 

The 1100 MDT, 2001 June 19 Pre-Test data were included for completeness. The following are 

the four sections of Appendix B: 

• Figures B1–B6: 2001 June 19 

• Figures B7–B12: 2001 June 20 

• Figures B13–B18: 2001 June 21 

• Figures B19–B24: 2001 June 22 
38 

Figures B1–B6: 2001 June 19-Rawinsonde Data 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity (%)

Height (m-AGL)

RH - 1100 MDT

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

200 210 220 230 240 250 260 270 280 290 300 310

Ambient (K) and Dewpoint Temperature (K) 

Height (m-AGL)

Ambient Temp 1100 MDT

Dewpoint Temp 1100 MDT

Figure B2. Thompson Tower RAOB Launch -2001 June 19: Relative Humidity.

Figure B1. Thompson Tower RAOB Launch-2001 June 19: Temperature.
39 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 90 180 270 360

Wind Direction (deg)

Height (m-AGL)

WD - 1100 MDT

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 2 4 6 8 10 12 14 16 18 20

Wind Speed (m/s)

Height (m-AGL)

WS - 1100 MDT

Figure B3. Thompson Tower RAOB Launch-2001 June 19: Wind Speed.

Figure B4. Thompson Tower RAOB Launch-2001 June 19: Wind Direction.
40 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

-35 -30 -25 -20 -15 -10 -5 0 5 10 15

Environmental Lapse Rate (K/km)

Height (m-AGL)

E L R 1100 MDT

Zero Line

Figure B6. Thompson Tower RAOB Launch-2001 June 19: ELR.

Figure B5. Thompson Tower RAOB Launch-2001 June 19: Pressure.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

100 200 300 400 500 600 700 800 900

Pressure (mb)

Height (m-AGL)

P - 1100 MDT
41 

Figures B7–B12: 2001 June 20-Rawinsonde Data 

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50 60 70 80 90 100

Relative Humidty (%)

Height (m-AGL)

RH - 0510 MDT

RH - 0746 MDT

RH - 0910 MDT

Figure B8. Thompson Tower RAOB Launch-2001 June 20: Relative Humidity.

Figure B7. Thompson Tower RAOB Launch-2001 June 20: Temperature.

0

1000

2000

3000

4000

5000

6000

7000

200 210 220 230 240 250 260 270 280 290 300 310

Ambient (K) and Dewpoint Temperature (K)

Height (m-AGL)

Ambient Temp 0510 MDT

Dewpoint Temp 0510 MDT

Ambient Temp 0746 MDT

Dewpoint Temp 0746 MDT

Ambient Temp 0910 MDT

Dewpoint Temp 0910 MDT
42 

0

1000

2000

3000

4000

5000

6000

7000

0 2 4 6 8 10 12 14 16 18 20

Wind Speed (m/s) 

Height (m-AGL)

WS - 0510 MDT

WS - 0746 MDT

WS - 0910 MDT

Figure B9. Thompson Tower RAOB Launch-2001 June 20: Wind Speed.

Figure B10. Thompson Tower RAOB Launch-2001 June 20: Wind Direction.

0

1000

2000

3000

4000

5000

6000

7000

0 90 180 270 360

Wind Direction (deg)

Height (m-AGL)

WD - 0510 MDT

WD - 0746 MDT

WD - 0910 MDT
43 

0

1000

2000

3000

4000

5000

6000

7000

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Environmental Lapse Rate (K/km)

Height (m-AGL)

E L R 0510 MDT

E L R 0746 MDT

E L R 0910 MDT

Zero Line

0

1000

2000

3000

4000

5000

6000

7000

100 200 300 400 500 600 700 800 900

Pressure (mb)

Height (m-AGL)

P - 0510 MDT

P - 0746 MDT

P - 0910 MDT

Figure B12. Thompson Tower-2001 June 20: ELR.

Figure B11. Thompson Tower RAOB Launch-2001 June 20: Pressure.
44 

Figures B13–B18: 2001 June 21-Rawinsonde Data 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity (%) 

Height (m-AGL)

RH - 0523 MDT

RH - 0738 MDT

RH - 0932 MDT

RH - 1055 MDT

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310

Ambient (K) and Dewpoint Temperature (K) 

Height (m-AGL)

Ambient Tem p 0523 MDT

Dewpoint Temp 0523 MDT

Ambient Tem p 0738 MDT

Dewpoint Temp 0738 MDT

Ambient Tem p 0932 MDT

Dewpoint Temp 0932 MDT

Ambient Tem p 1055 MDT

Dewpoint Temp 1055 MDT

Figure B13. Thompson Tower RAOB Launch-2001 June 21: Temperature.

Figure B14. Thompson Tower RAOB Launch-2001 June 21: Relative Humidity.
45 

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Zero Line

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WS - 0523 MDT

WS - 0738 MDT

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WS - 1055 MDT

Figure B16. Thompson Tower RAOB Launch-2001 June 21: Wind Direction.

Figure B15. Thompson Tower RAOB Launch-2001 June 21: Wind Speed.
46 

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E L R 0738 MDT

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E L R 1055 MDT

Zero Line

Figure B17. Thompson Tower RAOB Launch-2001 June 21: Pressure.

Figure B18. Thompson Tower RAOB Launch-2001 June 21: ELR.
47 

Figures B19–B24: 2001 June 22-Rawinsonde Data 

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Dewpoint Temp 0950 MDT

Figure B19. Thompson Tower RAOB Launch-2001 June 22: Temperature.

Figure B20. Thompson Tower RAOB Launch-2001 June 22: Relative Humidity.
48 

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Figure B22. Thompson Tower RAOB Launch-2001 June 22: Wind Direction.

Figure B21. Thompson Tower RAOB Launch-2001 June 22: Wind Speed.
49 

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Figure B23. Thompson Tower RAOB Launch-2001 June 22: Pressure.

Figure B24. Thompson Tower RAOB Launch-2001 June 22: ELR.
50 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing 

data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate 

or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, 

Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware 

that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a 

currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

May 2003

2. REPORT TYPE

Final

3. DATES COVERED (From - To) 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Surface Layer Stability Transition Research, Maximum Time Delay from 

Sunrise/Non-Ideal Conditions: 2001 June Case Study 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

Gail-Tirrell Vaucher, Manny Bustillos 

5f. WORK UNIT NUMBER 

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

U.S. Army Research Laboratory 

Computational & Information Sciences Directorate 

Battlefield Environment Division (ATTN: AMSRL-CI-EI) 

h S d l 88002 0

8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

ARL-TR-2823 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

U.S. Army Research Laboratory 

2800 Powder Mill Road 

Adelphi, MD 20783-1145

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

ARL-TR-2823

12. DISTRIBUTION/AVAILABILITY STATEMENT 

Approved for public release; distribution is unlimited.

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

Near surface target acquisition and EO propagation significantly improve during the Surface Layer Stability Transition (SLST). 

Thus, this research expands Army Chief of Staff Shinseki’s vision from “to see first” to, “to see better.” The SLST is also the 

starting and ending points for the atmospheric convection growth phase, an important factor in chemical warfare modeling. 

In 2001, the Meteorological-sensors Integration Team of the Army Research Laboratory conducted the second of three field 

tests with the primary purpose of characterizing, modeling and exploiting repeatable patterns in the lower portion of the 

atmospheric boundary layer. The repeatable patterns investigated were the morning Stability Transitions (ST) or Neutral Events

(NE). The 2001 June 20–22 test dates were selected based on a forecasted maximum time interval between the local Sunrise 

and an Ideal case NE. Two other field tests addressed the minimum Sunrise-to-NE time interval (March and September). These 

Tests are documented separately. 

The SLST Research pursued two measurement and analysis methods: Eulerian (Tower data) and quasi-Lagrangian (Rawinsonde 

data). The June results were as unexpected as the atypical Monsoon weather conditions observed. Excellent examples of 

Extended and Multiple STs were quantified by the data. A ST lasting at least 26 minutes surprised scientists by occurring well

before sunrise and the morning twilight. The cumulative findings over this 2001 Solstice time period have expanded the 

documented character of a desert stable-neutral-unstable morning transition. The information in this report is a useful building 

block in support of the primary goal. 

15. SUBJECT TERMS

Stability Transition, Neutral Events, Non-Ideal Conditions, Boundary Layer, Extended and Multiple Neutral Events 

16. SECURITY CLASSIFICATION OF: 

19a. NAME OF RESPONSIBLE PERSON

Gail-Tirrell Vaucher 

a. REPORT 

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b. ABSTRACT 

U 

c. THIS PAGE 

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505-678-3237 

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