Surface Layer Stability Transition Research, Minimum 

Time Delay from Sunrise: 2001 March Case Study 

by Gail-Tirrell Vaucher, Manny Bustillos, Alfred Gutierrez

ARL-TR-2798 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 88002-5513

ARL-TR-2798 May 2003 

Surface Layer Stability Transition Research, Minimum 

Time Delay from Sunrise: 2001 March Case Study 

Gail-Tirrell Vaucher, Manny Bustillos, Alfred Gutierrez 

Computational and Information Sciences Directorate, ARL 

Approved for public release; distribution is unlimited.

iii

Contents 

Contents iii

List of Figures iv

Preface vii

Acknowledgments viii

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 Minimum Test 9

2.1 2001 March Equinox-Atmospheric Surface Layer Test Overview.................................9 

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

2.3 11 

Test Summary.........................................................................................................................11 

3. Discussion Of Results 12

3.1 Eulerian and Lagrangian Data Acquisition ...................................................................12 

3.2 Defining the Stable, Neutral, Unstable Sub-Cases........................................................12 

3.3 2001 March Equinox Test-Synoptic Scale Conditions .................................................13 

3.4 Stable Sub-case Results.................................................................................................13 

3.4.1 A Eulerian View (Stable) ..................................................................................13 

3.4.2 A Lagrangian View (Stable)..............................................................................14 

3.5 Neutral Sub-case Results...............................................................................................15 
iv

3.5.1 A Eulerian View (Neutral) ................................................................................15 

3.5.2 A Lagrangian View (Neutral)............................................................................15 

3.6 Unstable Sub-case Results.............................................................................................16 

3.6.1 A Eulerian View (Unstable) ..............................................................................16 

3.6.2 A Lagrangian View (Unstable) .........................................................................16 

4. Summary and Conclusions 17

4.1 Neutral Event Forecast Model Validation.....................................................................17 

4.2 Characterizing the Morning Stability Transition...........................................................18 

4.2.1 Stable Sub-cases ................................................................................................18 

4.2.2 Neutral Sub-cases..............................................................................................18 

4.2.3 Unstable Sub-cases............................................................................................19 

5. Conclusions 19

Acronyms 20

References 22

Appendix A. Thompson Tower Data 25

Appendix B. Rawinsonde Data 43

Report Documentation Page 55 

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 February1995 June. ..................................................................................................................................5 

Figure 3. Monthly Averaged Sunrise Neutral Event Time Differences, 1994 April1995 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 March 19: Temperature. .......................................................26

Figure A2. Thompson Tower-2001 March 19: Relative Humidity ...............................................26 
v

Figure A3. Thompson Tower-2001 March 19: Wind Speed. ........................................................27 

Figure A4. Thompson Tower-2001 March 19: Wind Direction....................................................27 

Figure A5. Thompson Tower-2001 March 19: Solar Radiation....................................................28

Figure A6. Thompson Tower-2001 March 19: Delta-T ................................................................28 

Figure A7. Thompson Tower-2001 March 19: Pressure. ..............................................................29 

Figure A8. Thompson Tower-2001 March 19: ELR. ....................................................................29

Figure A9. Thompson Tower-2001 March 20: Temperature ........................................................30 

Figure A10. Thompson Tower-2001 March 20: Relative Humidity .............................................30 

Figure A11. Thompson Tower-2001 March 20: Wind Speed. ......................................................31 

Figure A12. Thompson Tower-2001 March 20: Wind Direction..................................................31 

Figure A13. Thompson Tower-2001 March 20: Solar Radiation..................................................32 

Figure A14. Thompson Tower-2001 March 20: Delta-T. .............................................................32 

Figure A15. Thompson Tower-2001 March 20: Pressure. ............................................................33 

Figure A16. Thompson Tower-2001 March 20: ELR. ..................................................................33 

Figure A17. Thompson Tower-2001 March 21: Temperature. .....................................................34 

Figure A18. Thompson Tower-2001 March 21: Relative Humidity. ............................................34 

Figure A19. Thompson Tower-2001 March 21: Wind Speed. ......................................................35 

Figure A20. Thompson Tower-2001 March 21: Wind Direction..................................................35 

Figure A21. Thompson Tower-2001 March 21: Solar Radiation..................................................36 

Figure A22. Thompson Tower-2001 March 21: Delta-T. .............................................................36 

Figure A23. Thompson Tower-2001 March 21: Pressure. ............................................................37 

Figure A24. Thompson Tower-2001 March 21: ELR. ..................................................................37 

Figure A25. Thompson Tower-2001 March 22: Temperature. .....................................................38

Figure A26. Thompson Tower-2001 March 22: Relative Humidity. ............................................38 

Figure A27. Thompson Tower-2001 March 22: Wind Speed. ......................................................39 

Figure A28. Thompson Tower-2001 March 22: Wind Direction..................................................39 

Figure A29. Thompson Tower-2001 March 22: Solar Radiation..................................................40 

Figure A30. Thompson Tower-2001 March 22: Delta-T. .............................................................40 

Figure A31. Thompson Tower-2001 March 22: Pressure. ............................................................41 

Figure A32. Thompson Tower-2001 March 22: ELR. ..................................................................41 

Figure B1. Thompson Tower RAOB Launch-2001 March 19: Temperature. ..............................44 

Figure B2. Thompson Tower RAOB Launch-2001 March 19: Relative Humidity. .....................44 

Figure B3. Thompson Tower RAOB Launch-2001 March 19: Wind Speed. ...............................45 

Figure B4. Thompson Tower RAOB Launch-2001 March 19: Wind Speed. ...............................45 
vi

Figure B5. Thompson Tower RAOB Launch-2001 March 19: Pressure. .....................................46 

Figure B6. Thompson Tower RAOB Launch-2001 March 19: ELR. ...........................................46 

Figure B7. Thompson Tower RAOB Launch-2001 March 20: Temperature. ..............................47 

Figure B8. Thompson Tower RAOB Launch-2001 March 20: Relative Humidity. .....................47 

Figure B9. Thompson Tower RAOB Launch-2001 March 20: Wind Speed. ...............................48 

Figure B10. Thompson Tower RAOB Launch-2001 March 20: Wind Direction.........................48 

Figure B11. Thompson Tower RAOB Launch-2001 March 20: Pressure. ...................................49 

Figure B12. Thompson Tower RAOB Launch-2001 March 20: ELR ..........................................49 

Figure B13. Thompson Tower RAOB Launch-2001 March 21: Temperature. ............................50 

Figure B14. Thompson Tower RAOB Launch-2001 March 21: Relative Humidity. ...................50 

Figure B15. Thompson Tower RAOB Launch-2001 March 21: Wind Speed. .............................51 

Figure B16. Thompson Tower RAOB Launch-2001 March 21: Wind Direction.........................51 

Figure B17. Thompson Tower RAOB Launch-2001 March 21: Pressure. ...................................52 

Figure B18. Thompson Tower RAOB Launch-2001 March 21: ELR. .........................................52 

Figure B19. Thompson Tower RAOB Launch-2001 March 22: Temperature. ............................53 

Figure B20. Thompson Tower RAOB Launch-2001 March 22: Relative Humidity. ...................53 

Figure B21. Thompson Tower RAOB Launch-2001 March 22: Pressure. ...................................54 

Figure B22. Thompson Tower RAOB Launch-2001 March 22: ELR. .........................................54 
vii

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. Within this publication, the authors present the key results and 

understandings gained from the 2001 March Equinox-Atmospheric Surface Layer Field 

Test, which was conducted by the Meteorological-sensors Integration Team at White 

Sands Missile Range, NM. 

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 electro-optical 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. 
viii

Acknowledgments 

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

for their successful execution of the 2001 March Equinox-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, 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 the first 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 Surface Layer. The 

repeatable pattern that focused the investigation was the morning Stability Transition 

(ST) period, or Neutral Event (NE). The 2001 March 19–22 time period was specifically 

selected based on a forecasted minimal time interval between the local Sunrise and an 

Ideal case ST. The two subsequent field tests addressed the maximum (June 2001) and 

the second minimal (September 2001) time interval between the local Sunrise and an 

Ideal case ST. These latter Tests will be documented individually in future technical 

reports. 

To characterize the repeatable ST pattern, two perspectives were pursued in the 

measurements and the analyses: a Eulerian and a quasi-Lagrangian approach. The 

ongoing ST modeling effort was enhanced by the validation point provided by the 2001 

March Equinox-Atmospheric Surface Layer Test for the Ideal NE Forecast Model. 

While the exploitation of the ST is beyond the purpose of this technical report, the 

information documented here does serve as a useful building block in support of that 

primary goal. 
2

1. Introduction 

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 

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 fullwidth 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 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 
3

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 

This document is the first of three technical reports stemming from a study with the 

governing purpose of characterizing, modeling and exploiting the lower portion of the 

Atmospheric Boundary Layer, the Surface Layer. The specific Surface Layer activity 

being investigated was the ST. This report presents the key results and new 

understandings gained from the 2001 March Equinox-Atmospheric Surface Layer Field 

Test conducted by the Meteorological-sensors Integration Team (MIT) of the U.S. Army 

Research Laboratory (ARL). This Test was executed at the Thompson Tower site (Lat: 

32.35, Long: –106.47), in White Sands Missile Range (WSMR), NM. One of the 

primary goals of this field test was to validate the proposed Seasonal Algorithm used in 

forecasting the exact time of the morning ST (Vaucher and Endlich, 1995). A 

mechanism for describing the unique nature of the Surface Layer is turbulence (Tatarski, 

1961). The dynamics of turbulence affects the Surface Layer stability, which impacts the 

U.S. Army’s ability to function efficiently. Thus, the fruit of this investigation feeds both 

the scientific goals of better understanding the evolution of the Atmospheric Boundary 

Layer, and the U.S. Army’s need to improve their efficiency by exploiting the natural 

character/patterns of the Atmospheric Boundary and Surface Layers. 
4

1.4 Background of the Stability Transition Study 

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 inversions that delayed the transition into the near-dry 

adiabatic atmosphere required for a NE. During the Equinox, the 24-h heating-cooling 
5

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 the 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 non-desert 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 pattern (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 
8

atmosphere to become isothermal and “neutral.” Cn

2

, coincidently, drops to a minimum. 

This is the morning, or Sunrise AOT NE. 

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 
9

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. 

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

duration was anywhere from 1 min to over 20 min. In a future ARL technical report 

documenting the 2001 June Solstice-Atmospheric Surface Layer Test, evidence will be 

given to show that neutral atmospheric conditions can exist 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 Minimum Test 

2.1 2001 March Equinox-Atmospheric Surface Layer Test Overview 

The 2001 March Equinox-Atmospheric Surface Layer Test was conducted 19–22 March 

2001 at the 100 ft Thompson Tower site, in WSMR, NM. The participants of the Test 

included the members of MIT, David Tofsted of ARL’s Weather Exploitation Branch, 

and SFC DJ James. The Test Coordinator was Gail Vaucher. The three purposes of the 

Test, with each respective point-of-contact (POC), were: 

(1) To be the first 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 

night-to-day transition period (POC: Doyle “Scott” Elliott). 

(3) To assess the relationship between observed angle-of-arrival variance, as derived 

from collected imagery and scintillometer-measured Cn

2

, in support of image 

modification code validation (POC: David Tofsted). 
10

Prior to the field test execution, a 1 km scintillometer path from Thompson Tower was 

scouted using global positioning system (GPS) location sensors. The resulting path 

represented the most consistent desert terrain covering. A 4 m scaffolding was installed 

at both the start (Thompson Tower) and the end (Ammo Site) of this path. Reciprocal 

scintillometer sensors were assembled and mounted at the 4 m levels. The temporary 

housing for the computer equipment at the remote Ammo Site was provided by a 

Commercial Utility Cargo Vehicle with shelter (known locally as “the pig”). 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. A manufacturer’s 

delay in the arrival of purchased scintillometer computer cards prohibited local Cn

2

 data 

acquisition during the test. However, all of the groundwork for the Cn

2

 acquisition was in 

place. 

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 at the 2 m and ~ 38 

m levels. Vaisala GPS rawinsondes were launched from a High Mobility Multi-wheeled 

Vehicle (HMMWV) situated west of Thompson Tower. A 25 kW Quiet Generator 

powered the HMMWV. The HST was placed north and slightly west of Thompson 

Tower. This versatile trailer served as the location for Post-test data processing and the 

Tester’s Conference Room. 

2.2 Test Execution 

A Pre-Test check of equipment and data acquisition was conducted on 19 March 2001. 

Test Days 1–3 (2001 March 20–22) began at 0400 Mountain Standard Time (MST), with 

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

served to minimize desert dust around the data acquisition field site. Two data 

acquisition case studies were scheduled (0500, 0700 MST) and successfully executed. 

Case I (0500 MST) characterized the pre-dawn desert atmosphere. Case II (0700 MST) 

coincided with the actual, onsite atmospheric NE. A third case (0800 MST) was added 

during the Post-Test analysis (See Section 3.2). 

On Test Day 1 only, an early morning WSMR Multiple Launch Rocket System (MLRS) 

mission forced the Case II (0700 MST) RAOB to originate from the WSMR Desert Site 

location. As an added benefit to the coincident ARL/WSMR missions, RAOB data were 

also acquired for the hours of 0900 and 1100. 

The Thompson Tower data for all cases ran uninterrupted. All RAOBs for Test Days 2 

and 3 were launched at the Thompson Tower site. 

An Internal Project Review concluded this field test. 
11

2.3 Test Summary 

The following summarizes the initial test results, as per the mission statements. 

Mission 1. “Day #1 (actual Equinox day) predicted the NE to occur at 0703 

MST. The temperature differences radioed to the ground observer 

reported the single-point NE timing to be 07:03:30 MST. Insolation 

measurements reported that the sky was completely void of any visible 

cloud. The NEs for Days #2 and #3 were delayed due (in part) to the 

occulting effects of cirrus on the eastern horizon.” (See Appendixes 

A and B). 

Mission 2. “The Thompson Tower data acquisition was successful for all 

three Test Days (6 cases). A preliminary review of the insolation, 

thermodynamic and wind data acquired from both the 2 and 38 m tower 

levels quantitatively characterized the desert Surface Layer during the 

night-to-day transition period.” (Appendix A). 

Mission 3. “Assessing the relationship between the observed angle-of arrival 

variance as derived from collected imagery, and Cn

2 measured by 

scintillometer, was halted due to the lack of available parts for the 

reciprocal scintillometer sensors. A Post-Test effort to attain and install 

these missing elements was set in motion, with the next targeted deadline 

of 2001 June Solstice Test.” (Vaucher, 2001). 
12

3. Discussion Of Results 

3.1 Eulerian and Lagrangian Data Acquisition 

The data acquisition for this Experiment/Test took the form of both a Eulerian approach 

(sampling a fixed volume of atmosphere) and a quasi-Lagrangian approach (following a 

parcel of air). 

The data acquired from sensors mounted on Thompson Tower provided the Eulerian 

view of the morning ST. The resulting time-series of Pressure (P), Temperature (T), 

Relative Humidity (RH), Wind Speed (WS), Wind Direction (WD) and Solar Radiation 

(SR) are displayed in Appendix A. Delta-Temperature (Delta-T) and Environmental 

Lapse Rate (ELR) time-series were added during the Post-Experiment analysis. 

A rawinsonde (RAOB) is a helium-filled, balloon-borne meteorological sensor package 

that samples a vertical profile of the atmosphere by following the ambient airflow. The 

atmosphere being traced by the RAOB is not a closed system, therefore, one might refer 

to this data resource as a quasi-Lagrangian approach. The data acquisition results 

characterized the vertical atmospheric structure for each case, yielding vertical profiles of 

P, T, RH, WS and WD. A profile of the ELR was calculated as part of a Post-Test 

Analysis (Appendix B). 

3.2 Defining the Stable, Neutral, Unstable Sub-Cases 

For a Post-Test statistical analysis, each Test Day was sub-divided into Stable 

(Nighttime), Neutral, and Unstable (Daytime) case studies. The definition for each subcase was a function of both thermodynamics and solar attributes, and are as follows: 

Stable (Nighttime): The T difference (T38m–T2m) was positive. SR measurements were 

equivalent to zero. The duration of data extracted for this case was 1-h. 

Neutral: The center point of this case was when the 38–2 m T difference passed through 

zero. Thirty minutes of data prior to and after this event were included in this case. 

Unstable (Daytime): The Delta-T recorded was negative. Sampled SR magnitudes were 

increasing with time. Since the field experiment data acquisition was often terminated 

prior to a full hour, a 30-min duration was considered acceptable for this case. 

For the 2001 March-Equinox Test, the general data acquisition times for these three subcases were approximately 0500–0600 MST (Stable), 0630–0730 MST (Neutral), and 

0800–0830 MST (Unstable). The following section summarizes the results of the three 

days of data by their Sub-case. Note that all parameter magnitudes used in the discussion 

are AVERAGED values for that particular Sub-case. 
13

3.3 2001 March Equinox Test-Synoptic Scale Conditions 

The following information was taken from several professional weather Web sites. The 

resources consisted primarily of weather charts and summaries. 

Synoptic conditions for 20–21 March included an upper level ridge over the southwestern 

states. Storm systems were being diverted far to the north of WSMR. Good surface 

heating under clear skies set up a three-day warming trend. Moisture over the southwest 

was sparse. Locally, weather conditions for the 24-h period were sunny and warm in the 

morning, mostly sunny and warm with light winds later in the day. Sunrise was at 0609 

MST. 

By Day 2 (21–22 March), the ridge aloft had weakened and there was the developing of a 

nor’easter over the Carolinas. The northern extent of the ridge was limited by the jet 

stream stretching from the Pacific-Northwest across the northern tier. The ridge showed 

periodic flattening, as weak impulse-energy moved through. Locally, 21 March was 

partly cloudy in the morning, becoming mostly sunny by midday, with warm 

temperatures, and mostly light to occasionally breezy winds. Sunrise was at 0608 MST. 

The final Test day saw a strong west-northwesterly jet stream along the western United 

States and Canadian border extending over the northern plains. A weak shortwave had 

moved into California and was projected toward the Four Corners region of NM. Lowlevel convergence, and the strengthening of mid-level lapse rates increased the morning’s 

partly cloudy skies to cloudiness by the afternoon, with mountain showers threatening the 

area. Local winds were light to breezy. Sunrise was at 0607 MST. (Forecast for White 

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

3.4 Stable Sub-case Results 

3.4.1 A Eulerian View (Stable) 

By definition, the SR for all three of the Stable atmospheric Sub-cases (2001 March 20–

22) was zero (no sun). 

The (averaged) 38 m and 2 m T magnitudes agreed with the synoptic analysis by 

displaying a systematic increase over the three-day period. The largest increase occurred 

between Day 2 and 3. Maximum-minimum temperatures for both levels over this 1-h 

case generally spanned 1o

, with small variances. By Day 3, the temperature range had 

increased to approximately 2.5o

. Also, the top (.74) and bottom (.97) variances were the 

largest of the three days. A calculation of the Top-Bottom T covariance and correlation 

coefficient (R) values showed little correlation between these two levels. 

The Stable Sub-case (averaged) Delta-T values for Days 1–3 were +4.1 K (σ = 0.54), 

+6.0 K (σ = 0.32), and +6.7 K (σ = 1.26), respectively. 
14

The RH displayed a drying trend over the three-day period. Not surprisingly, the greatest 

humidity was sampled near the surface, where the coldest temperatures were reported. 

The averaged 2 m RH was approximately double that of the 38 m RH. Variance 

magnitudes at both the upper and lower levels were small. 

The WSs for both upper and lower levels were less than 2 m/s. Averaged WD was 

primarily northwesterly, implying a drainage flow from the Tularosa Basin’s neighboring 

mountains. On Day 3, the averaged surface wind was less than 0.5 m/s, rendering little 

significance to the WD average. 

3.4.2 A Lagrangian View (Stable) 

The Stable 0500 MST Sub-case RAOB launches for Days 1–3 began at 0510, 0506, and 

0546 MST, respectively. Ascent rates for the 3 cases were about 3 m/s, with collection 

periods lasting 67, 25, and 23 min. The P profile showed no significant variation 

between the three Stable Sub-cases, implying no upper level fronts. Boundary Layer P 

change with height was consistently –0.1 mb/m. In fact, no significant P variation was 

seen for any of the cases. 

The surface temperature inversions increased each day of the test (30.92, 36.20 and 76.85 

K/km). Between Day 1 and Day 2, the height of the inversion increased from 359 to 442 

m. However, in Day 3, the inversion strength had more than doubled and did so within 

about half the height of the first 2 days. 

All three days of Stable Sub-case RH profiles displayed the expected negative RH lapse 

rate (–50, –30, –75%/km, respectively). The depths of the decreasing humidity were 359, 

1083, 254 m. Isohume layers below 1 km were abundant (10–23 layers) throughout each 

of the days. 

Airflow gently accelerated with height in both Stable wind profiles acquired (Day 1 and 

Day 2). The maximum WS was 3.2 and 5 m/s. Not far above this feature, and just below 

the weak capping inversion, was a distinct jet that had a magnitude of approximately 

double the lowest level jet. Minor WS maxima framed this larger jet on Day 1. 

Including the gently increasing surface flow, Day 2 also had minor WS maxima framing 

the larger jet. 

The WD showed no consistent attributes. For Day 1, the 0–1 km WD was backing 

(counterclockwise) with height. From 1–3 km, there was an oscillation between 

northwest and north. On Day 2, the entire profile was primarily westerly. 
15

3.5 Neutral Sub-case Results 

3.5.1 A Eulerian View (Neutral) 

Only Day 1 reported clear skies. Day 1 (averaged) SR was the lowest magnitude of the 

Test: 155 W/m2. Cloud cover was observed on Days 2 and 3, delaying the NE timing. 

Averaged SR yielded values of 229 and 204 W/m2. The increased magnitude was 

interpreted as primarily a function of the neutral Sub-case time period. 

The averaged Delta-T was 0.2 K (σ = 1.9 K) for the first two days, and 0.5 (σ = 1.9 K) for 

the last day. Delta-T ranges for the three days were +3.5 to –2.1 K, +3.8 to –1.8 K, and 

+4.6 to –1.8 K, respectively 

Top (38 m) and bottom (2 m) RH were at their highest on Day 1 (32% and 53%, 

respectively). The drying trend of Days 2 and 3 placed their RH at less than 35%, with 

the lowest layer being moister. Winds were from the northern quadrants (drainage) and 

averaged values less than 2 m/s. 

3.5.2 A Lagrangian View (Neutral) 

The criterion for the Neutral Case RAOB release time was that it would occur when the 

38 m and 2 m Thompson Tower Delta-T registered 0 K. Unfortunately, Day 1 RAOB 

release time was dictated by the more expensive WSMR MLRS mission, and Day 3 

RAOB release time was also delayed. Ultimately, while Day 2 was coincident with the 

isothermal Tower measurement crossover, the other 0700 MST Cases were only an 

approximation to a Neutral Atmosphere. 

The Neutral Sub-case temperature inversion strengths for these three days (21.6, 14.7 and 

15.8 K/km) were significantly less than the Stable Sub-cases. The number of temperature 

inversions below 3 km for these days were 4, 2 and 1, respectively. Isothermal layers 

reported were 3, 2, and 1, respectively. Day 2 was distinguished from the others in that if 

one allows for a +/–0.1 K correction to the temperature data, then the strength of the 

surface inversion would be reduced to 9.0 K/km. This is most encouraging in that the 

Day 2 RAOB launch most closely coincided with the ST reported by the Thompson 

Tower data. Note that an Ideal NE for optical propagation at the original research site 

was empirically determined to be under near dry adiabatic. 

All three Test days sampled the greatest RH near the surface. The height of peak RH 

magnitudes varied from just above the surface, to 1.5–2 km above ground level (AGL). 

Also, Isohume layers were still abundant (7–17 layers). 

Wind data were available for just the first two days. The strong wind maxima noted in 

the Stable Sub-cases were still present in the Neutral Sub-case. Two weaker flows were 

present below the stronger air stream on Day 1. These held the same directions as the 
16

Stable Sub-case. Day 2’s weaker flow near the surface was primarily southwesterly, with 

a distinct westerly flow dominating the 1–5 km (boundary and free atmosphere) layers. 

3.6 Unstable Sub-case Results 

3.6.1 A Eulerian View (Unstable) 

The Unstable Sub-cases for Day 2 and Day 3 occurred at nearly the same time. 

Therefore, it is no surprise that the SR values were similar (431 and 463 W/m2). Data 

availability placed the Unstable Sub-case of Day 1 data about 30 min earlier. 

Consequently, the SR is only 304 W/m2. Interestingly, the averaged Delta-T for Day 1 

and Day 2 are both –1.6 K (Day 3 is –1.9 K). 

The RH for the earlier Unstable Sub-case (Day 1) was observed to have the greatest 

magnitude at the lower level (a Neutral and Stable characteristic). Day 2 and Day 3’s RH 

were notably drier. Top and Bottom measurements for both days had the same values, 

factoring in the relatively small standard deviation (< 1%). Without the adjustment, Day 

2 bottom RH was slightly greater than the top RH, and Day 3 bottom RH was slightly 

less than the top RH. 

Calm to light-and-variable winds were observed during all 3 days. 

3.6.2 A Lagrangian View (Unstable) 

Day 1 was the only day with Unstable Sub-case RAOB data. As expected, no surface 

temperature inversion was present. Instead, the Surface ELR was –10.7 K/km. The 

lowest level temperature inversion was reported as +1.4 K between 243 and 498 m AGL. 

The ELR for this inversion was +5.5 K/km. Two isothermal layers preceded the only 

other Boundary Layer temperature inversion (1916–2053 m). An isothermal layer, 54 m 

thick, lay above this upper level inversion, making the full layer 1916–2107 m. This 

upper level feature (ELR = 2 K/km) was presumed to be the capping inversion. 

The increasing RH, with height peaked at 243 m AGL, the base of the decaying nocturnal 

inversion layer. From 243 to 2053 m, the RH displayed a drying trend. Only 6 Isohume 

layers were sampled within the first km. 

The wind profile displayed the same low-level jet framed by two weaker flow maxima 

patterns seen in both the Stable and Neutral Sub-cases. The magnitude was 

approximately half that of the Stable Sub-case’s low-level jet. The WD for this jet was 

northeast. The smaller currents were northwest. 
17

4. Summary 

In July 2002, the U.S. Army Chief of Staff Shinseki stated that his vision for the current 

and future 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). One of the 

greatest hurdles to seeing first is the atmosphere. Depending on the atmospheric 

conditions, the atmosphere can be a friend or a foe. The Boundary Layer ExploitationAtmospheric Stability Transition Research defines the naturally occurring friendly and 

non-friendly atmospheric conditions, and is one link in the non-trivial effort of 

discriminating between them as they pertain to military applications. In fact, by 

differentiating between the friendly and non-friendly atmospheric conditions, ARL 

expands U.S. Army Chief of Staff Shinseki’s vision from “to see first,” to, “to see better.” 

Under friendly atmospheric conditions, the identification of targets can theoretically be 

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

efficient and more effective. 

The ST study has further military applications in the powerful laser weapons arena, as 

well as the area of chemical and biological weapons hazards plaguing urban warfare. By 

knowing the timing and characteristics of the STs, the atmospheric impact, i.e. whether 

the weapon’s effectiveness will be enhanced or diminished, can be better evaluated. 

Likewise, establishing the initial conditions of the convective Boundary Layer growth 

phase (the ST) is of primary interest to both the civilian and military Convective 

Boundary Layer and other Atmospheric Dispersion/Diffusion Modelers. Results from 

these time-evolving models often reflect the accuracy of their initial starting points. For 

the military, knowing when a smoke screen will disperse, for example, could prove to be 

a significant strategic advantage on a battlefield. Thus, the exploitation of the ST pattern 

ties to several military and civilian interests and applications (Angevine et al., 2001). 

This document is the first of three technical reports stemming from a study with the 

governing purpose of characterizing, modeling and exploiting the lower portion of the 

Atmospheric Boundary Layer, the Surface Layer. The specific Surface Layer activity 

being investigated was the ST. The March Equinox time period was selected because of 

its previous statistical association with the minimal amount of time observed between 

local sunrise and a NE, under Ideal desert atmospheric conditions. 

4.1 Neutral Event Forecast Model Validation 

The question of whether the NE Forecast Algorithm developed in the mid-1990s at 

HELSTF, NM was site-specific was partially answered during the only Ideal Case 
18

observed (Day 1). Here, the forecasted and observed times were coincident. The 

occulting of the sun by clouds on the eastern horizon prohibited any further Ideal 

Condition NE Forecast Algorithm validation. 

4.2 Characterizing the Morning Stability Transition 

Characterizing the atmosphere undergoing a ST was another objective of this study. The 

strategy employed for this effort was to contrast three sub-cases: Nighttime (Stable), 

Neutral, and Daytime (Unstable) conditions. Two perspectives on these 3 sub-cases were 

examined: a Eulerian and a quasi-Lagrangian approach. 

Measurements for the Eulerian approach came from tower data sampled at two levels (38 

m and 2 m). The quasi-Lagrangian perspective was provided by rawinsonde data 

initiated at or near Thompson Tower for each of the stability sub-cases. 

4.2.1 Stable Sub-cases 

The 60 min of Eulerian data characterized the Stable sub-cases as having no SR (by 

definition), a 38 m minus 2 m Delta-T of +4 to +7 K, greatest moisture near the surface 

with very small variances, winds that were light and from the directions typical of a 

drainage flow off the neighboring mountains. 

The Lagrangian Stable Sub-case data reported strong surface inversions ranging between 

30 and 77 K/km. The RH concurred, with the greatest RH near the surface, in addition to 

several layers of Isohume conditions. The vertical wind profile showed one major lowlevel jet framed by weaker flow maxima. Drainage flow was implied. 

4.2.2 Neutral Sub-cases 

The fixed-point perspective centered the 60 min of Sub-case data on the actual observed 

transition. Averaged SR for the Ideal case was 155 W/m2

. The Non-ideal cases reported 

larger values. Not surprisingly, the averaged Delta-T magnitudes hovered around the 

positive side of 0 K for all three sample sets. The ranges for the Delta-T began around +4 

K, and decreased to approximately –2 K. The greatest RH was found near the surface. 

Winds were light and tending to be from the northern sectors (implying drainage). 

The Lagrangian perspective presented the surface temperature inversions between +14 

and +22 K/km. Other inversions and isothermal layers were present within the Boundary 

Layer vertical profiles. The RH continued to show the moister layer to be near the 

surface, with several Isohume layers within the Boundary Layer. The gross features of 

the wind profile were very similar to the Stable Sub-case. The characteristic low-level 

jet, however, was at a higher level than the Stable Sub-case. 
19

4.2.3 Unstable Sub-cases 

The SR was approximately double that of the Neutral Sub-cases. The Delta-T 

magnitudes were around –2 K. The RH presented mixed results. One case maintained 

the greatest humidity near the surface (clear skies), while the other two showed a more 

homogenous structure. Winds were calm to light-and-variable for all three days. 

A single data source provided the Lagrangian perspective. These data sampled a surface 

lapse rate of –11 K/km, an elevated inversion (ELR = +6 K/km) and a capping inversion 

of about +2 K/km. The RH profile peaked at the base of the first inversion and had the 

fewest reported Isohume layers within the Boundary Layer of the Sub-cases. The 

Unstable wind profile propagated the pattern of the Stable and Neutral Sub-cases. That 

is, the data reported a strong, low-level jet framed by two weaker flow maxima. 

5. Conclusions 

Conclusions are best drawn from a completed data set. This document presents only onethird of the study’s results. While the authors were very much encouraged by the single 

point Ideal Conditions validation of the NE Forecast Model, the resource was only a 

single point and must be kept in perspective. The characterizing of the March conditions 

was helpful in that a foundation or standard for contrast has been etched. Once the next 

two pieces of this atmospheric puzzle are completed, a gleaning of conclusions will be 

pursued. 
20

Acronyms 

AOT Atmospheric Optical Turbulence 

ASL Atmospheric Surface Layer 

ARL U.S. Army Research Laboratory 

AGL Above Ground Level 

Cn2 Index of Refraction Structure Function 

Delta-T Temperature Difference [T38m – T2m] 

ELR Environmental Lapse Rate 

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 

MLRS Multiple Launch Rocket System 

MST Mountain Standard Time 

NE Neutral Event 

P Pressure 

RAOB Rawinsonde Observation System 

RH Relative Humidity 

SLST Surface Layer Stability Transition 

SR Solar Radiation 

SRNE Sunrise Neutral Event 

ST Stability Transition 

T Temperature 
21

WS Wind Speed 

WSMR White Sands Missile Range 

WD Wind Direction 
22

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. 

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, Maximum Time Delay from Sunrise: 2001 June Case Study; Technical 

Report No: ARL-TR-2823, 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. 
23

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

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

Battlefield 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 March 2001) White Sands Meteorology Branch, WSMR Weather 

Support Center. 

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

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

 University Corp for Atmospheric Research. 
24
25

Appendix A. Thompson Tower Data 

This appendix is part of ARL-TR-2798, Surface Layer Stability Transition Research 

Minimum Time Delay from Sunrise: 2001 March 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 time-series data. Sampling was executed at 2 m and 38 m above ground level 

(AGL). For convenience, we have designated data representing the lower layer 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 MST 

 Neutral 0630–0730 MST 

 Unstable 0800–0830 MST 

The Pre-Test data acquired on 2001 March 19 were included with the scheduled Test 

(20–22 March) for completeness. The following are the four sections of Appendix A: 

• Figures A1–A8: 2001 March 19 

• Figures A9–A16: 2001 March 20 

• Figures A17–A24: 2001 March 21 

• Figures A25–A32: 2001 March 22 
26

Figures A1–A8: 2001 March 19-Thompson Tower Data

Figure A1. Thompson Tower-2001 March 19: Temperature. 

0

10

20

30

40

50

60

70

80

90

100

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Relative Humidity (%)

RH [38m]

RH [2m]

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

15

16

17

18

19

20

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Temperature (C)

Temp [38m]

Temp [2m]
27

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

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

0

1

2

3

4

5

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Wind Speed (m/s)

WS [2m]

-90

0

90

180

270

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Wind Direction (deg)

WD [2m]
28

Figure A5. Thompson Tower-2001 March 19: Solar Radiation. 

Figure A6. Thompson Tower-2001 March 19: Delta-T. 

0

100

200

300

400

500

600

700

800

900

1000

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Solar Radiation (W/m^2) -10

-8

-6

-4

-2

0

2

4

6

8

10

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hr)

Delta-Temperature (K)

Delta-T [38m - 2m]

Zero Line
29

Figure A7. Thompson Tower-2001 March 19: Pressure. 

-70

-65

-60

-55

-50

-45

-40

-35

13 14 15 16 17

Local Time (Dec Hr)

Environmental Lapse Rate (K/km)

E L R (C/km)

Figure A8. Thompson Tower-2001 March 19: ELR. 

881

882

883

884

13.00 14.00 15.00 16.00 17.00

Local Time (Dec Hrs)

Pressure (mb)

P [33.8m]
30

Figures A9–A16: 2001 March 20-Thompson Tower Data

Figure A9. Thompson Tower-2001 March 20: Temperature. 

Figure A10. Thompson Tower-2001 March 20: Relative Humidity. 

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Temperature ( C )

Temp [38m]

Temp [2m]

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Temperature ( C )

Temp [38m]

Temp [2m]

0

10

20

30

40

50

60

70

80

90

100

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Relative Humidity (%)

RH [2m]
31

Figure A11. Thompson Tower-2001 March 20: Wind Speed. 

Figure A12. Thompson Tower-2001 March 20: Wind Direction. 

0

1

2

3

4

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Wind Speed (m/s)

WS [2m]

-180

-90

0

90

180

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Wind Direction (deg)

WD [2m]
32

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

Figure A14. Thompson Tower-2001 March 20: Delta-T. 

0

100

200

300

400

500

600

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Solar Radiation (W/m^2) -10

-8

-6

-4

-2

0

2

4

6

8

10

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Delta-Temperature (K)

Delta-T [38m-2m]

Zero Line
33

881.5

882.5

883.5

884.5

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Pressure (m/b)

P [33.8m]

Figure A15. Thompson Tower-2001 March 20: Pressure. 

-100.0

-50.0

0.0

50.0

100.0

150.0

200.0

250.0

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Environmental Lapse Rate [K/km]

Env. Lapse Rate

Zero Line

Figure A16. Thompson Tower-2001 March 20: ELR. 
34

Figures A17–A24: 2001 March 21-Thompson Tower Data

Figure A17. Thompson Tower-2001 March 21: Temperature. 

Figure A18. Thompson Tower-2001 March 21: Relative Humidity. 

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hr)

Temperature ( C )

Temp [38m]

Temp [2m]

0

10

20

30

40

50

60

70

80

90

100

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]
35

Figure A19. Thompson Tower-2001 March 21: Wind Speed. 

Figure A20. Thompson Tower-2001 March 21: Wind Direction. 

0

1

2

3

4

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Wind Speed (m/s)

WS [38m]

WS [2m]

-180

-90

0

90

180

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Wind Direction (deg)

WD [38m]

WD [2m]
36

Figure A21. Thompson Tower-2001 March 21: Solar Radiation. 

Figure A22. Thompson Tower-2001 March 21: Delta-T. 

0

100

200

300

400

500

600

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Solar Radiation (W/m^2)

-10

-8

-6

-4

-2

0

2

4

6

8

10

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Delta - Temperature (K)

Delta-T [38m-2m]

Zero Line
37

879

880

881

882

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Pressure (m b)

P [33.8m] 

Figure A23. Thompson Tower-2001 March 21: Pressure. 

-100.0

-50.0

0.0

50.0

100.0

150.0

200.0

250.0

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Environm ental Lapse Rate (K/km )

Env Lapse Rate

Zero Line

Figure A24. Thompson Tower-2001 March 21: ELR. 
38

Figures A25–A32: 2001 March 22-Thompson Tower Data

Figure A25. Thompson Tower-2001 March 22: Temperature. 

Figure A26. Thompson Tower-2001 March 22: Relative Humidity. 

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Temperature (C)

Temp [38m]

Temp [2m]

0

10

20

30

40

50

60

70

80

90

100

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Relative Humidity (%)

RH [2m]
39

Figure A27. Thompson Tower-2001 March 22: Wind Speed. 

Figure A28. Thompson Tower-2001 March 22: Wind Direction. 

0

1

2

3

4

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Wind Speed (m/s)

WS [38m]

WS [2m]

-180

-90

0

90

180

4.00 5.00 6.00 7.00 8.00 9.00 Local Time (Dec Hrs)

Wind Direction (deg) 

WD [38m]

WD [2m]
40

Figure A29. Thompson Tower-2001 March 22: Solar Radiation. 

Figure A30. Thompson Tower-2001 March 22: Delta-T. 

-10

-8

-6

-4

-2

0

2

4

6

8

10

4.00 5.00 6.00 7.00 8.00 9.00 Local Time (Dec Hrs)

Delta-Temperature (K)

Delta-T [38-2m]

Zero Line

0

100

200

300

400

500

600

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Solar Radiation (W/m^2)
41

876

877

878

879

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Pressure (m b)

P [33.8m] 

Figure A31. Thompson Tower-2001 March 22: Pressure. 

-100.0

-50.0

0.0

50.0

100.0

150.0

200.0

250.0

4.00 5.00 6.00 7.00 8.00 9.00

Local Time (Dec Hrs)

Environm ental Lapse Rate (K/km )

Env Lapse Rate

Zero Line

Figure A32. Thompson Tower-2001 March 22: ELR. 
42
43

Appendix B. Rawinsonde Data 

This appendix is part of ARL-TR-2798, Surface Layer Stability Transition Research 

Minimum Time Delay from Sunrise: 2001 March Case Study, U.S. Army Research 

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

A quasi-Lagrangian (following the parcel) perspective on the atmospheric conditions 

during the Nighttime (Stable) to Daytime (Unstable) transition was quantitatively 

recorded by the Thompson Tower site Rawinsonde (RAOB) data. The RAOB data, 

referenced as ‘C-station,’ were released at the White Sands Missile Range Desert Site 

(about 5 miles northeast 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. We have purposefully elected 

to follow the rainbow’s spectrum to make data viewing easier. As a reminder, the 

general times designated for each Sub-case were: 

 Stable 0500–0600 MST 

 Neutral 0630–0730 MST 

 Unstable 0800–0830 MST 

The 1540 MST Pre-Test data flight on 2001 March 19 was included for completeness. 

The following are the four sections of Appendix B: 

• Figures B1–B6: 2001 March 19 

• Figures B7–B12: 2001 March 20 

• Figures B13–B18: 2001 March 21 

• Figures B19–B22: 2001 March 22 
44

Figures B1–B6: 2001 March 19-Rawinsonde Data

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

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

0

1000

2000

3000

4000

5000

6000

7000

220 230 240 250 260 270 280 290 300

Ambient (K) and Dewpoint Temperature (K)

Height (m-AGL)

Ambient Temp 1540 MST

Dewpoint Temp 1540 MST

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity (%)

Height (m-AGL)

R H - 1540 MST
45

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

Figure B4. Thompson Tower RAOB Launch-2001 March 19: Wind Speed. 

0

1000

2000

3000

4000

5000

6000

7000

0 5 10 15 20 25 30

Wind Speed (m/s)

Height (m-AGL)

W S - 1540 MST

0

1000

2000

3000

4000

5000

6000

7000

-180 -90 0 90 180

Wind Direction (deg)

Height (m-AGL)

W D - 1540 MST 

Zero Line
46

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

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

0

1000

2000

3000

4000

5000

6000

7000

100 200 300 400 500 600 700 800 900

Pressure (mb)

Height (m-AGL)

P - 1540 MST

0

1000

2000

3000

4000

5000

6000

7000

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

Environmental Lapse Rate (K/km)

Height (m-AGL)

L P R 1540 MST

Zero Line
47

Figures B7–B12: 2001 March 20-Rawinsonde Data

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

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

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

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

Ambient (K) and Dewpoint Temperature (K)

Height (m-AGL)

Ambient Temp - 0510 MST

Dewpoint Temp - 0510 MST

Ambient Temp - 0715 MST

Dewpoint Temp - 0715 MST

Ambient Temp - 0914 MST

Dewpoint Temp - 0914 MST

Ambient Temp - 1151 MST

Dewpoint Temp - 1151 MST

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 - 0510 MST

RH - 0715 MST

RH - 0914 MST

RH - 1151 MST
48

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

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

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 5 10 15 20 25 30

Wind Speed (m/s)

Height (m-AGL)

WS - 0510 MST

WS - 0715 MST

WS - 0914 MST

WS - 1151 MST

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

-90 0 90 180 270

Wind Direction (deg)

Height (m-AGL)

WD - 0510 MST

WD - 0715 MST

WD - 0914 MST

WD - 1151 MST

Zero Line
49

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

Figure B12. Thompson Tower RAOB Launch-2001 March 20: ELR 

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 - 0510 MST

P - 0715 MST

P - 0914 MST

P - 1151 MST

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

-30 -20 -10 0 10 20 30 40 50 60 70

Environmental Lapse Rate (K/km)

Height (m-AGL)

E L R - 0510 MST

E L R - 0715 MST

E L R - 0914 MST

E L R - 1151 MST

Zero Line
50

Figures B13–B18: 2001 March 21-Rawinsonde Data

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

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

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 - 0506 MST

RH - 0721 MST

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

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

Ambient (K) and Dewpoint Temperature (K)

Ambient Temp - 0506 MST

Dewpoint Temp - 0506 MST

Ambient Temp - 0721 MST

Dewpoint Temp - 0721 MST

Height (m-AGL)
51

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

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

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 5 10 15 20 25 30

Wind Speed (m/s)

Height (m-AGL)

WS - 0506 MST

WS - 0721 MST

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 - 0506 MST

WD - 0721 MST
52

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

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

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 - 0506 MST

P - 0721 MST

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

-20 -10 0 10 20 30 40 50 60 70 80

Environmental Lapse Rate (K/km)

Height (m-AGL)

E L R - 0506 MST

E L R - 0721 MST

Zero Line
53

Figures B19–B22: 2001 March 22-Rawinsonde Data

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

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

0

1000

2000

3000

4000

5000

6000

7000

220 230 240 250 260 270 280 290 300

Ambient (K) and Dewpoint Temperature (K)

Height (m-AGL)

Ambient Temp - 0546 MST

Dewpoint Temp - 0546 MST

Ambient Temp - 0724 MST

Dewpoint Temp - 0724 MST

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity (%)

Height (m-AGL)

RH - 0546 MST

RH - 0724 MST
54

Figure B21. Thompson Tower RAOB Launch-2001 March 22: Pressure. 

Figure B22. Thompson Tower RAOB Launch-2001 March 22: ELR. 

0

1000

2000

3000

4000

5000

6000

7000

100 200 300 400 500 600 700 800 900

Pressure (mb)

Height (m-AGL)

P - 0546 MST

P - 0724 MST

0

1000

2000

3000

4000

5000

6000

7000

-20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

Environmental Lapse Rate (K/km)

Height (m-AGL)

E L R - 0546 MST

E L R - 0724 MST

Zero Line
55 

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, Minimum Time Delay from Sunrise: 

2001 March Case Study

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

Gail-Tirrell Vaucher, Manny Bustillos, Alfred Gutierrez 

5f. WORK UNIT NUMBER 

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

U.S. Army Research Laboratory 

Information Science and Technology Directorate 

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

White Sands Missile Range, NM 88002-5501

8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

ARL-TR-2798 

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-2798

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 first 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 March 20–22 test dates were selected based on a forecasted minimal time interval between the local Sunrise and an Ideal 

case NE. Two subsequent field tests addressed the maximum (June) and a second minimum (September) Sunrise-to-NE time 

interval. These latter Tests are documented separately. 

The Surface Layer Stability Transition research pursued two measurement and analysis methods: Eulerian (Tower data) and 

quasi-Lagrangian (Rawinsonde data). The results included validation data for the Ideal Neutral Event Forecast Model and a 

characterization of a desert stable-neutral-unstable morning transition over the Equinox time period. The information 

documented here serves as a useful building block in support of the primary goal.

15. SUBJECT TERMS

Stability Transition, Neutral Events, Delta-T, Lapse Rate 

16. SECURITY CLASSIFICATION OF: 

19a. NAME OF RESPONSIBLE PERSON

Gail-Tirrell Vaucher 

a. REPORT 

U

b. ABSTRACT 

U 

c. THIS PAGE 

U 

17. LIMITATION 

 OF 

 ABSTRACT 

SAR 

18. NUMBER 

 OF 

 PAGES 

67 19b. TELEPHONE NUMBER (Include area code) 

505-678-3237 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.1