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Produced by the NASA Center for Aerospace Information (CASI)
ya

y^'

December 1984

Analysis of the NASA/ MSFC 

Airborne Doppler Lidar Results

from San Gorgonio Pass Califotnia

(NASA-ca-171355) ANAL YS I S OF T HE NASA/NSFC

AIBBOFbd CCPPLEF IILAh RESUITS FROM SAN

GORGONIO PASS, CAIIFCFNIA Final beport

(Pacific AorthwEst Lat.) 7C F HC A04/hF A01

N85-2 1E73

0

Unc la s

,7 14445

Prepared for the National Aeronautics and Space

Administration, Marshall Space Flight tenter

under Contrast 2311104780

P10. 4F tte^se

Pacific Northwest laboratories
R

R: Analysis of the NASA/MSFC

Airborne Doppler Lidar Results

from San Gorgonio Pass California

W. C. Cliff

J. R. Skarda

D. S. Renne

W. F. Sandusky

December 1984

Prepared for

the National Aeronautics

and Space Administration

Marshall Space Flight Center, MSFC, AL 35812

under Contract 2311104780

NASA Contract NASB-34733 V

Battelle

Pacific Northwest Laboratories

Richland, Washington 99352

a
Acknowledgements

The authors wish to express their gratitude to Dr. James C. Dodge of the

NASA HQ OSST-Mesoscale Atmospheric Processes Research Program who prcvided for

this effort. This effort was directed and sponsored by the NASA/MSFC

Atmospheric Sciences Division headed by Dr. William W. Vaughan. Dr. Dan

Fitzjarrald was NASA's CDR for this project and provided much direction and

encouragement during the effort. Special thanks is extended to each of these

individuals and the countless other NASA personnel that made these

measurements possible including Dr. George H. Fichtl of NASA/MSFC, who

pioneered much of the program definition; Jinn Bilbro lead NASA/MSFC Doppler

Lidar En g ineer, Ed Weaver Principal Investigator of the NASA/MSFC Doppler

Lidar Severe Storms Measurement Program, and George Alger of NASA/HMES who

managed the aircraft operations.

The authors also wish to acknowledge and thank the Southern California

Edison Utility for their support of this effort under the direction of Bob

Yinger.

Special thanks is also acknowledged for the support the DOF Federal Wind

Energy Program provided through its wind characteristic program element headed

by Dr. Larry 'Wendell of PNL.

- 

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2

Executive Summary

Two days during July of 1981 the NASA/MSFC Airborne Doppler Lidar System

(ADLS) was flown aboard the NASA/AMES Convair 990 on the east side of San

Gorgor 4 o Pass California, near Palm Springs, to measure and investigate the

accelerated atmospheric wind field discharging from the pass.

The ADLS used a pulsed CO 2 laser with a 10.6 w m wavelength. The pulse

repetition rate was 140 times a second with a 2u sec pulse length. The

return, from the laser light scattered by naturally occurring aerosols, was

gated to give a spatial resolution of approximately 300 meters. The Doppler

frequency shift of the returned light is a measure of the along axis component

of the atmospheric velocity field. The two dimensional horizontal wind field

was observed by rotating the beam first to an angle of 20 0 in front of a

normal to the aircraft, then to an angle of 20 0 behind a normal to the

aircraft, both in a horizontal plane. This technique produced a cross hatched

(checkerboard) spatial picture of the horizontal wind field 3t each location

where the path of a forward pulse and the path of a rE arward pulse crossed.

The two along axis component velocities measured at each pulse path c-ossing

were used to produce a horizontal wind field. The vectors are a checkerboard

spatially separated, both parallel and normal to the aircraft flight path, at

about 300 meters.

These tests were conducted to examine the vertical and horizontal extent

of the fast moving atmospheric flow discharging from the San Gorgonio Pass.

k

Conventional ground measurements were also taken during the tests to assist in

validating the ADLS results. This particular region is recognized as a high

wina resource region and, as such, a knowledge of the horizontal and vertical

extent of this flow was of interest for wind energy applications. The

statistics of the atmospheric flow field itself as it discharges from the pass

I

and then spreads out over the desert were also of scientific interests. This

data provided the first spatial data for ensemble averaging of spatial

correlations to compute longitudinal and lateral inte g ral length scales in the

Ilongitudinal and lateral directions for both components. (These results will

be discussed later in this executive summary.)

r
3

M

The mean wind field was of fundamental interest. The followina fi g ure is

a plot of the horizontal wind field issuing from San Gorgonio Pass, near and

over Palm Springs, obtained by the ADLS system.

ruac♦ wti[T IS Y1.

s

it .4 . a 30' ^ 5 e

Fun: l,i

Date: 07 30 1981

Time: 00 25 02

Origin

Longitude 116 45

Latitude: 33 45

all 600< Radar Altitude <750 Meters

,P Sigma < 1.0

s,

R 6

^

nd Palrrtl

Atmospheric Wind Field Discharging From San Gorgonio Pass

The pass is near the left center of the figure, with north being at the

top of ,,he f gure. The flow is seen to dischar g e orto the desert uniformly

from the north of the pass, however, south of the pass the flow turns south

and follows the mountain contours down over the Palm Springs area.

Mean winds observed with the ADLS in the vicinity of the pass were of the

order of 13 m/s at an elevation of about 700 meters above g rade. Ground truth
4

data taken from towers indicated a wind speed of approximately 13 m/s at 46

meters and kite data taken at 10U meters also indicated a wind speed of

approximately 13 m/s. Power law profiles with coefficients of about 0.10 tend

to exist near the ground but the profile quickly flattens and in some cases

show a slightly negative exponent at higher elevations. This is as expected

for accelerated and decelerated flow through a pass. The flow

acceleration/deceleration provide the dominant flow effects as opposed to

normal boundary layer growth from the pass floor dominating the velocity

profile. The ground based tower data thus supports the ADLS data and thereby

provides some validation of the ADLS mean wind data.

There has been some speculation as to whether the spread in the Doppler

spectrum of the ADLS could be used as a direct measure of the turbulence

within the focal volume. In an attempt to evaluate this speculation high

resolution data were taken on ground towers and analyzed for times

corresponding to 300 meters of wind pass , ng over the sensors. (The 300 meters

co r responds to the pulse length in which the variations from discrete particle

returns would cause spread in the Doppler spectrum.) The tower data indicated

a velocity RMS of approximately 1 m/s. This value was slightly lar g er than 1

m/s at a height of 10 meters and had fallen to about .9 m/s at a height of 46

meters. Outside of the constant shear region this value is expected to

continue to decrease due to dissipation exceeding production as well as the

fact that the turbulent length scale is increasin g and thus the percent energy

for the same high wavenumber region of interest will be less (i.e., the larger

the integral scale the more energy is associated ::iih lower wavenumbers).

The average RMS of the Doppler spread was about 1.7 m/s. There are,

however, several other phenomena that contribute to the Doppler spread (e.g.,

the finite residence time that the scattf:ring sources ire in the sensing

volume, the finite pulse length, etc.). Thus, the analysis of this test data

indicates that additional thought is required before one can conclusively use

the Doppler spread for assessing the turbulence level within the beam

resolution volume (pulse length).

I For decades scientists have estimated spatial statistics by takin g time

i

histories and then using Taylor's Hypothesis to transform the time history

into a synthetic space history. Perhaps one of the greatest scientific

I-•.

I
5

achievements of the ADLS system is its ability to produce a spatial field of

wind vectors from which true spatial correlations and length scales may be

computed.

Large areas directly at the pass exit and over Palm Springs were analyzed

separately for their spatial properties. The flow over Palm Springs provides

a nonaccelere ing flow field while the flow exiting the pass provides a

dilitating or decelerating flow. The lateral length scale in the pass was

computed to be roughly the same but slightly larger than the longitudinal

length scale. (That is, the lateral component correlated in the lateral

direct i on compared to the longitudinal component cor r elated in the

longitudinal direction.) Over the desert near Palm Springs the traditional

effect of the longitudinal length scale being the larger was observed.

The following are the authors' conclusions based upon the analysis of the

NASA Airborne DLS data taken at San Gorgonio Pass.

. The NASA/ADLS measi.red horizontal wind fields are creditable.

The NASA/ADLS provides unique spatial sensing of atmospheric

properties previously unattainable.

Spatial correlations and length scales have been computed at the San

Gorgonio Pass exit and near Palm Springs.

The following are the authors' recommendations for future use of the

NASA/ADLS.

. The NASA/ADLS be used to study flow over and about complex terrain.

The NASA/ADLS be used to measure atmospheric flows fields to provide

verification data for numerical codes used to:

1) Predict potential dispersion of releases from nuclear power

plants.

2) Predict dispersion and concentrations of discharges from coal, gas

and diesel fired turbines and power plants.
6

TABLE OF CONTENTS

SECTION PAGE

Acknowledgement. 1

Executive Summary 2

Table of Contents 6

List of Tables 7

List of Figures. 8

1.0 Historical Background 10

2.0 Introduction 12

2.1 Region Description 12

2.2 Doppler Lidar Description 13

3.0 Summary of Results, Conclusions and Recommendations. 18

4.0 Test Procedure 20

5.0 Wind Vector Analysis and Results 27

5.1 Doppler Lidar RE;u'ts 28

5.2 Ground Truth Data 36

6.0 Correlation Analysis and Results 42

7.0 Atmospheric Length Scales 61

Literature Cited 63

Appendix A: Test Plan for NASA's Airborne Doppler

Lidar System (ADLS) Testing in the San

Gorgonio Pass Area. 64

^I

^D s a+ ^ ry^i..Y% w .w, 
7

LIST OF TABLES

N

TABLE NO. TITLE PAGE

1.:

1 Header Record for San Gogonio Flights. 24

2 Pulse Data Record. 25

3 Mean Flow Results for Run 13 and 14

(Over Palm Springs and San Gorgonio Pass). 34

4 Standard Deviations of Flow Results for Run 13

and 14 (Over Palm Springs and San Gorgonio Pass) 35

5 Summary of Power Law Coefficients (a). 37

6 Average-Mean, RMS Turbulent Intensities for

Various Elevations and Time Intervals

(Approximate Space Intervals). 39

7 Integral Length Scales. 62

IL_I :. I
a.; i

8

LIST OF FIGURES

FIGURE 140. TITLE PAGE

1 Block Diagra, .<,F Airborne Doppler Lidar System. 14

2 Spectral Parametars Calculated by the Signal

Processor 16

3 Airborne Doppler Lidar Scan Pattern 21

4 Expanded View of Airborne Doppler Scan Pattern. 22

5 Horizontal Wind Field Exiting San Gorgonio Pass

(Flight 20, Run 13, Elevation 650m) 29

6 Horizontal Wind Field Exiting San Gorgonio Pass

Plotted on U.S.G.S. Topography Map (Flight 20,

Run 13, Elevation 650m) 30

7 Horizontal Wind Field Exiting San Gorgonio Pass

(Flight 20, Run 14, Elevation 800n) 31

8 Horizontal Wind Field Exitin^ San Gorgonio Pass

Plotted on a U.S.G.S. Topography Map (Flight 20,

Run 14, Elevation 800n) 32

9 Correlation Procedure 44

10 Average Autocorrelation of Longitudinal Component

in the Longitudinal Direction over Palm Springs

(Flight 20, Run 13, Elevation 650m) 45

11 Average Autocorrelation of Longitudinal Component

in the Longitudinal Direction over Palm Springs

(Flight 20, Run 14, Elevation 800m) 46

12 Average Autocorrelation of Longitudinal Component

in the Lateral Direction over Palm Springs

(Flight 20, Ru •

13) 47

13 Average Autocorrelation of Longitudinal Component

in the Lateral Direction over Palm Springs

(Flight 20, Rur. 14) 48

14 Average Autocorrelation of Lateral Component

in the Lateral Direction over Palm Springs

(Flight 20, Run 13) 49

15 Average Autocorrelation of Longitudinal Component

in the Lateral Direction over Palm Springs

(Flight 20, Run 14)

-b kV7V4A_ 
9

LIST OF FIGURES (continued)

FIGURE NO. TITLE PAGE

16 Average Autocorrelation of Longitudinal Component

►, in the Longitudinal Direction over Palm Springs

(Fli , lht 20, Run 13) 51

17 Average Autocorrelation of Lateral Component

in the Longitudinal Direction over Palm Springs

(Flight 20, Run 14) 52

18 Average Autocorrelation of Longitudinal Component

in the Longitudinal Direction over San Gorgonio

Pass Exit (Flight 20, Run 13) 53

' 19 Average Autocorrelation of Longitudinal Component

in the Longitudinal Direction over San Gorgonio

Pass Exit (Flight 20, Run 14) 54

20 Average Autocorrelation of Longitudinal Conponent

in the Lateral Direction over San Gorgonio Pass

Exit (Flight 20, Run 13) 55

21 Average Autocorrelation of Longitudinal Component

in the Lateral Direction over fan 'Jorgonio Pass

Exit (Flight 20, Run 14) 56

22 Average Autocorrelation of Lateral Component 

in the Lateral Direction over San Gorgonio

Pass Exit (Flight 20, Run 13) 57

23 Average Autocorrelation of lateral Component

in the lateral Direction over San Gorgonio

Pass Exit (Flight 20, Run 14) 58

24 Average Autocorrelation of Lateral Component

in the Longitudinal Direction ever San Gorgonio

Pass Exit (Flight 20, Run 13) 59

25 Average Autocorrelation of Lateral Component

in the Longitudinal Direction over San Gorgonio

Pass Exit (Flight 20, Run 14) 60

I
10

ANALYSIS OF THE NASA/MSFC AIR30RNE. DOPPLER LIDAR RESULTS

FROM1 SAN GORGON 10 )ASS CALIFORNIA

by

William C. Cliff

J. Raymond Skarda

David S. Renne

William Sandusky

1.0 HISTORICAL BACKGROUND

Two decades ago (1964) H. Yeh and H. Z. Cummings (1) published their

experimental results which demonstrated that coherent laser systems could be

- used to accurately measure fluid velocities. The potential for this new

technology was quickly recognized by both private industry and by the federal

government labs. Similar programs/ concepts that were being pursued at this

same time by industry and government were accelerated and by the mid-60's

private industry was marketing small laboratory systems, which by now had

become known as Laser Doppler Yelocimeters (LDY), with measurement sensing

ranges of up to a few meters. Systems which could probe longer ran g es were

being pursued by government labs such as the NASA's Marshall Space Flight

Center and the Airforce's Arnold Engineering and Development Center. The

Arnold approach was to scale up one of the techniques which were being

effectively used in the laboratory. This was a system which comprised of a

laser beam being split ano the recombined at the desired sensing location.

Ranges of tens of meters have been achieved but the system was massive and

somewhat limited in capability. Over the years several investigators have

used this approach for atmospheric velocities with limited success.

At the same time a NASA team headed by Robert Milton Huffaker had been

working on a unique approach which used a continuous wave (CW) CO 2 -nle beam

laser system whic) transmitted the laser light and received the returned light

along the same optical path coaxial).

In the 1966-67 time frame the first signal return were measureu with the

CW-0O 2 coaxial system. Due to the the focal volume increasin g with increasing

focal aistance the rangE of this system is limited to about 400 meters.
11

Because many atmospheric applications reouire sensing at range: greater

than 50U meters, the design of a coaxial CO 2 pulsed system wa r. developed at

NASA/MSFC from 1969 to 1970. The system was first designed to look forward

from an ai rcraft to detect Clear Air Turbulence (CAT). The pulsed system was

fabricated and flown in 1972 and 1974 on the NASA/AMES Airborne Laboratory, a

convair 99U aircraft named Galileo. The CAT system was maraged by Ed Weaver

of NASA/MSFC, while Galileo was managed by Herb Cross NASA/ANZS. Two months

after the 1974 flight testing of the CAT system, a iiavy subchaser and the

Galileo collided in mid-air taking the lives of all on board the Galileo.

During the next few years NASA/AMES equipped another Convair 990 to becoloe

tneir new flying laboratory name Ctlileo II that carried the CAT system on a

1979 mission. 'IASA/MSFC continued the development of both their CW and pulsed

CO 2 coaxial Laser Dopp:2r Systems.

The pulsed system was improved and a scanning system was developed which

would tie directly into the inertial navigation system of the Galileo II.

During this period the development and use of NASA/MSFC Laser Doppler Systems

were under Or. William W. Vaughan and Dr, G. H. Ficht' with Ld Weaver still

managing the airborne system and Jim Bilbro becoming the lead engineer.

By 1981 the new scanning Airborne Laser Doppler System (now known as

Airborne Doppler Lidar) was ready for collecting data on she first set of

scientific experiments with Dr. Dan Fitzjarrald in charge of the experiments

which had been proposed by private industry, universities and other government

agencies. The Airborne Dop p ler Lidar System was fitted into the Galileo II in

Juice 1981 to perform tests associated with Dr. James Dodge's (NASA HQ) severe

storms program. The NASA/MSFC team was the same as given above and the

Galileo was no:. managed by George Alger as it was for the 1979 CAT flights.

During June and July of 1981 the Galileo would perform 21 fli g hts which

employed the Airborne Doppler Lidar. (2) On two of these fli g ht, July 10 and

July 29, the Airborne Doppler Lidar System measured the wind field exiting the

east end of San Gorgonio Pass, California. It is these tests and the analysis

of the Airborne Doppler Wind Data that are the subject of this report.

- 
12

{ 2.0 INTRODUCTION

2.1 Region Description

The San Gorgonio Pasi region was identified in October 1980 by NASA's

Seconcary Flows, Boundary Layers, Turbulence, Wave Team, as a region where the

atmospheric flow field was of scientific and practical significance and

interest. The San Gorgonio Pass is located approximately 200 Km (120 miles)

east of Los Angeles. The pass is about 40 Km (25 miles) long with a westerly

elevation of approximately 76U m (2500 ft) gradually dropping to an elevation

of approximately 200 m (700 ft). The width of the pass is roughly 8 Km (5

miles)Lat a contour approximately 300 m (1000 ft) above the pass floor]. The

east end the pass quickly broadens and becomes ope-i desert floor. Thy

mountains through which the pass penetrates rise to about 3350 Km (11,000 ft)

within 16 to 24 Km (10-15 miles) on each side of the pass floor. When the

marine inversion layer on the Los Angeles side builds to a depth greater than

the pass entrance elevation, the marine air be g ins flowing down the pass. The

flow is accelerated into and down the pass and then decelerates as it expands

onto the desert on the east side.

This region is well known for its extraordinarily strong winds and was

considered to potentially be a strong wind resource location. However for the

region to be a strong wind source location for multiple wind turbines spaced

in a direction parallel to the prevailing wind direction (ali g ned with the

pass), the high winds must be more than just strong surface winds. The strong

winds must extend to significant heights above g rade level. This is so that

there would be sufficient upper air momentum to replace the momentum extracted

by upwind wind turbines. This vertical extend of these strong winds along

with the spreading of these strong winds over the valley floor were the

practical interests of this atmospheric region.

Scientific objectives which were to be met by investigation of this

region were the examination of the atmospheric flow field as it diverged at

the pass exit and the comparison of these results with those obtained over the

desert region where the streamlines become straight and parallel. Since this

would be the first opportunity to examine detailed spatial wind fields in the

boundary layer, this region presented a unioue opportunity to examine spatial
13

correlations, both lateral and longitudinal at upper elevations for both the

diverging pass flow as well as over the desert floor. Other scientific items

of interest were to compare Doppler Lidar results with data obtained from

terrestrial measuring systems such as met towers equipped with conventional

anemometers and kites. Several of the other Airborne Doppler Lidar

experiments flown during the June-July 1981 time frame were also established

for comparin g the Airborne Doppler Lidar results with those obtained by other

measuring techniques such as Deal Doppler Radar with chaff as a tracer and

small plane measurement:. Since all tov^2r and kite type data provide only

temporal information, comparisons of the Doppler Lidar Data with tower or kite

data do require that time and space statistics be related throu g h Taylors

hypothesis (3) which states in part that "...one may assume that the sequence

of changes in u at a fixed point are simply due to the passage of an

unchanging pattern of turbulent niction over the point, i.e., one may assume u

= C t) = C x/U) where x :s measured upstreai,. at time t = 0 from the fixed point

where u is measured." Where u is the fluctuating portion of the veloc i ty, U

the mean velocity and t is time. With temporal and spatial mean velocities

being comparable by considering stationarity and continuity.

2.2 Airborne Doppler Lidar Description

The following description of the Airborne Doppler Lidar System used in

the San Gorgonio experiment is for the most part extracted from reference 2

courtesy of Jim Bilbro. A block diagram of the Airborne Doppler- Lidar System

(ADLS) is provided in figure 1.

The master oscillator is a small, 8 W cantinuous wave CO 2 laser operating

at a wavelength of 10.6 u m. A beam splitter permits a small portion of the

output of this laser to be used as a local oscillator which is shifted in

polarization by 9U 0 (not shown in Figure 1) then recombined with the scattered

return creating a time dependent interference pattern on a light sensitive

detector. The major portion of the laser beam is directed through an

electro-optic modulator, where it is amplitude-modulated to form a train of 2

us (330 m) long pulses. This laser pulse train passes through an optical

isolator, expander, and a series of six amplifier tubes.
14

MOOULAT'011 IgLAT011 I IR

AWL1F1ER

t11EWETER

0,011001111

OUARTlaWAVE KATE TILECOrE

NAtTER

OSCILLATOR DETECTOR CONTTROLLER

SCJ^NNER

LASER

CENTRAL

AMPl1FIER Ii

tTAOE

f10NAl

M«EfW7R

TIMING

AND CONTOOL

AIRCRAFT

wMIDOMI

SYETEN

A TTrOE111ERE

AIRCRAFT

DATA

VAMP

►ROCtsV D101^1

SVSTENE COMPUTER RECORDERS1

' OWLAYS

NAROconts

Figure 1. Block diagram of Airborne Doppler Lidar System. Broad arrows refer

to light signals and single -black arrows refer to electronic

signals (From Reference 2, CoLrtt:,y of J. Bilbro)
15

After exiting the amplifier, the laser pulses pass through a Brewster

window and quarter-wave plate. The pulses are then expanded and collimated by

a 30 cm, 01 aluminum, off-axis telescope to a diameter of 0.24 m (measured to

the 2 point of the Gaussian-shaped amplitude distribution). The pulses then

pass through two germanium wedges that allow scanning in a horizontal plane

20 0 forward and 20 0 aft of the telescope line-of-sight (which is normal to the

aircraft centerline). The pulses exit the aircraft through a germanium

window, which also serves as a pressure bulkhead. Once the pulses enter the

atmosphere, their light is scattered in all directions by aerosols typically

ranging from 1 to 10 μm in diameter. Some of the radiation is scattered back

along the axis of illumination, having been both phase and frequency shifted.

The amount that the frequency is shifted is called the Doppler shift or

Doppler frequency. The Doppler shift, Af, is proportional to the

line-of-sight velocity component of the scattering sources. The equation for

the Doppler shift as a function of tite line-of-sight component, V L , is: Af =

2VL/a.

The back-scattered radiation from measurement volumes (0.24 m diameter,

33U m length) is collected by the same telescope responsible for the

transmission. The radiation travels back through the quarter-wave plate to

the Brewster window, where it is reflected to a beam splitter (due to the fact

that at this location the returning li g ht is polarized 90 0 to the transmitted

light and is now reflected from the Brewster window, through which the

transmitted light passes). The returnin g radiation is then cc,nbined with the

local oscillator, and focused on the surface of a li q uid-nitrooen cooled

HgCdTe detector. The combination of the two beams results in an interference

pattern that varies in time according to the frequency difference between the

local oscillator and the back-scattered radiation. The output of the detector

is an FM signal, whose modulation is proportional to the Doppler shift

associated with the movcm.cnt of aerosols contained within the measurement

volume.

The detector output is amplified, and then the frequency analyzed using a

multiple band pass analyzer. At this time, three spectral parameters are

extracted. ThP^.e three spectral parameters are shown in Fi g ure 2 (Lee,

1 y 6(;) .
16

I F, = PEAK INTENSITY VALUE

F M = FREQUENCY ASSOCIATED WITH Ip

W = WIDTH

IF

U)z

F—

Z

FM

FREQUENCY

Figure 2. Spectral Parameters Calculated by the Signal Processor
17

The mean fre q uency shift is related to the mean aerosol line-of-sight

velocity, while the intensity is related to the back-scattered power. The

spectral width is estimated from the shape of the autocovariance by performing

• l a least-squares fit to a Gaussian distribution. A portion of the soectral

width relates to the spread in velocities in the measurement volume. Other

effects also cause the spectrum to broaden, (e.g., broadening due to the fact

that the data record is not infinite, broadening due to finite resonance time

of the aerosols, and others).

The on board inertial navigation system provides data to the Airborne

Doppler Lidar's Central Timing and Control Systems (CTCS) from which the

aircrafts pitch and roll are used to control the scanner position so that the

Doppler Lidar System scans only in a horizontal plane. The planes motion

relative to the ground, along with the beam direction, is used to compute the

Doppler frequency shift that results from the iiotion of the aircraft. This

frequency is then removed from the return Doppler frequency prior to

computation of the wind velocity.

i
18

3.0 SUMMARY OF RESULTS, CONCLUSIONS AND RECOMMENDATIONS

3.1 Results

The NASA Airborne Doppler Lidar System successfully measured the

horizontal wind field near the east side of San Gorgonio Pass,

California.

The depth of the accelerated flow from the San Gorgonio Pass was in

excess of 1 KM.

The atmospheric flow from the pass spreads out to follow the hills to

the south over Palm Springs but tends to discharge easterly at the

north side of the pass.

Ground data indicate that near surface flows channel somewhat down the

center of the pass.

Spatial correlations were computed from the ADLS data exiting the pass

as well as over Palm Springs.

Integral length scales of the wind field ra.ged from about 300 to 500

meters at elevations of 650-800 meters.

3.2 Conclusions

The NASA ADLS can accurately measure the horizontal wind field over

complex terrain with a grid point spacing of about 300 meters with a

range of about 10 KM (e.g., each pulse is sensed every 300 meters by

gating the return).

The NASA ADLS provides a unique capability for performing atmospheric

research with unique spatial resolution previously unattainable.

3.3 R(commendations

The NASA ADLS be used to study atmospheric flow fields over complex

terrain.
19

the NASA ADLS be used to measure atmospheric flow fields for

comparison, validation and upgrading of numerical codes used to

predict dispersion and concentrations from sources of concern (e.g.,

power plants, mining locations, etc.).

The NASA ADLS be used as a scientific tool for investigating

atmospheric turbulence and measuring atmospheric spectra and length

scales over uniform terrain for various surface roughness.

The NASA ADLS be used to study the flow behind large isol3tc•d knolls.

ITI
2U

4.0 TEST PROCEDURES

As was mentioned previously, the ADLS alternatively scans 20 0 forward and

then 2U 0 aft. It takes approximately 0.5 seconds for the scanning operation.

The length of time required for each fo;-ward or aft measurement depend, upon

the number of pulses one wishes to average. For the San Gorgonio flight 120

pulses were averaged for each measurF,nent.

A 4 second pulse was used with a repetition rate of 140 per second and a

gating of the return every 21j seconds. This enabled the system to provide

wind data about every 300 meters both parallel and normal to the planes

motion.

Figures 3 and 4 (courtesy J. Bilbro from Ref. 4) graphically depict the

scanning process used with the Airborne Doppler Lidar System.

A flight test plan was developed which utilized the ADLS' capability for

detailing the flow exiting the San Gorgonio Pass as well as flow over Palm

Springs. Appendix A is a copy of the test plan conceived for the San Gorgonio

tests. Ground data was to be taken at several locations throughout the San

Gorgonio region, including data from: 

a 100 meter meteorological tower in the pass

a 50 meter meteorological tower just downstream of the pass exix on

the north side of the pass

several 10 meter towers

several tala kites.

The fli g ht of the NASA Convair 990 was to be at elevations where the

aircraft was as low as possible to collect data that was as close to the

ground data as possible. The flight paths were also to be at higher

elevations to determine the vertical extent of the accelerated flow through

the pass.

The ADLS beam could also be locked at a slightly depressed angle enabling

a one dimensional look at velocities as a function of elevation. Several

tlight paths incorporating this feature were also su g gested in the test plan.

y_
10 YT

21

:~2Z' 1 Yw1

1

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^, V. • 2SO MIS

1

s0 S 1

Figure 3. Airborne Doppler Lidar Scan Pattern

(Courtesy of J. Bilbro, NASA/MSFC, Reference 4)

., 1 A r. 
- V A - 2!0 M/f

22

A v

Figure 4. Expanded View of Airborne Doppler Scan Pattern

(Courtesy of J. Bilbro, NASA/MSFC, Reference 4)
W..

23

Because of the tremendous amount of information being received durinq a

test, much onboard real time data compression and computing was performed.

Some additional data handling was performed at the Marshall Space Fliqht

Center (MSFC) with the reduced data for the various tests was then distributed

to the various ,)rincipal investigators.

Table 1 is a listing of the information provided on the magnetic tape

header record for the San Gorgonio flights, Table 2 is a listing of the

information provided on the data tape for each pulse. Note that each poilse is

i

range gated 45 times for the San Gorgonio tests. This means that the

atmospheric velocity was ampled at 45 locations along each pulse.
24

TABLE 1. HEADER RECORD FOR SAN GORGONIO FLIGHTS

WEIGHT

i

,I

WORD N NAME

1 Flia_ht +^

2 Run 0

3 Month

4 Day Fliqht Date

5 Year

5 Hours

6 Minutes Start Time

7 Seconds

b Hours

9 Minutes Stop Time

10 Seconds

11-90 Spare

t
t 25 ' TABLE 2. PULSF DATA RECORD

WORD 11 NAME WEIGHT 1 East Distance 20m 2 North Dis tance 20m 3 LOS .i j

4-11 Spare

12 LiJnr Amplitude Raw .1875 r;B

• 13 L-idar Velocity Raw .08 m/s

14 !ijar Width

1 (coded)

15 East Distance 20m

16 North Distance 20m

17S .001

18 Lidar Amplitude Threshold

and range corrected .1875

19 Lidar Velocity* .08 m/s

[0 C1

21 C2

22 C3 Smooth Coefficients .0000001

23 C4

24 Cr,

25 C5 Spare Coefficients

26 C7

27 East Distance Aovected** 20m

28 North Distance Ad^ected** 20m

29 Vorticity

30 Divergence

31 Stretch

32 Shear

b'ords 12-32 repeat 44 more

times once for each Bir.

957 Flight N1

958 Day 01

959 Run #

1

960 Time, Seconds .ls

961 Tine, Minutes from Midnight lm

962 Pressure Altitude 15,479 ft.

963 Spare

964 Radar Altitude

i ft.

965 Dew/Frost Point .loC

966 Static: Air Temp. .loC

967 1R Surface Temp. .loC

968 Total Air Temp. .loC

969 Latitude, Minutes .1 min.

970 Latitude, Degrees1 deg.

971 Longitude, Minutes .1 min.

972 Longitude, Degree,1 nea.

973 True Heading .044

974 True Air Speed

1 kts.

975 Ground Speed .1221 kts. 
26

TABLE 2. (continued)

NAME WEIGHT

Drift Angle .0439450

Wind Speed .1 kt

Wind Direction .10

Pitch .0439450

Roll .0439450

Wedge Angle, Inner .10

Wedge Angle, Outer .10

Time to Position 10

Sensor Motor Temp. .10C

LOS Elevation .10

Pulses Per Inte q ration 1

Number of Lags 1

Track .0439450

Lo Frequency .01

Off-set .08

Spare

WORD #

976

977

978

979

980

981

982

983

984

985

986

967

988

989

990

991
27

5.0 WIND VECTOR ANALYSIS AND RESULTS

The wind vector data for the San Gorgonio's test were collected usin g the

NASA ADLS system described in Section 2.2. A resolution of about 330 meters

was resolved along the lidar beam pulse by using a 0.2u sec pulse of the laser

and gating the return every 2.13u sec. The returned radiation is attributed

primarily to back scattering by aerosols ranging from 1 to IOum in diameter.

The difference between the frequencies of the transmitted and received

radiation are a linear measure of the radial (along beam) component of

velocity. This relation is given by: V radial = C of

where: V radial = radial (along beam) component of the atmospheric velocity

C = 2/a where a is 10.6um (the wavelenoth of the laser)

6f = the Doppler frequency (frequency difference of the

transmitted and received radiation).

The measurement volume (for each pulse) is a cylindrical region bound by the

pulse diameter and the resolution length R. R is approximated by: R=

1/2CT

where: C = speed of light (3x10 8 m/s)

T = Duration of receiver gate (2.13 s)

The factor 112, comes about by convolving the pulse length and the duration of

the gate.

The back-scattered radiation is the incoherent sum of all the scatters

within the measurement volume. Spectral analysis of the measurement volume

signal was performed on board the aircraft using the following three spectral

parameters: (a) mean doppler fre q uency, (b) intensity of return, and (c)

spectral width as described in Section 2.2. These parameters were averaged

over 140 pulses to get a mean spatial average along the flight path as well as

normal to the fli g ht path.

The doppler lidar beam directions were 20 0 forward and 20 0 aft of a

direction normal to the aircraft. The locations where a forward beam sampled

the atmosphere and subsequently the rearward beam sampled the atmosphere are

locations where the horizontal wind vector was computed.

14 
28

5.1 Doppler Lidar Results

The horizontal wind fields for the San Gorgonio ADLS tests were measured

using the techniques described in Section 2.2 and 5.0. The following results

are those obtained from NASA Flight 20, runs 13 and 14 which were performed on

July 29, 1981. The atmospheric horizontal wind fields from runs 13 are shown

in Figure 5 and 6 and the horizontal wind fields from run 14 are shown in

Figures 7 and 8.

Figure 5 shows only the measured horizontal wind field for run 13 while

Figure 6 shows the measured horizontal wind field plotted on a USGS

topographic map of the area. Similarly, Figure 7 is only the measured

horizontal wind field for run 14 while Figure 8 is the horizontal wind field

for run 14 superimposed on a USGS topographic map of the area. The ability to

overlay the horizontal wind field over a USGS topographic map is made possible

because the NASA ADLS system is tied to the aircrafts inertial navigation

system. From the knowledge of exactly where the plane is and a knowled g e of

the beam configuration relative to the plane, the location of each measurement

volume along each pulse is determined very accurately. It is perhaps at this

location in the report that one begins seeing the extreme sophistication and

potential worth of this state-of-the-art system.

A more detailed examination of the data was performed on both runs in the

regions of the flow issuing from the pass and the flow over Palm Springs.

These regions were examined in terms of their mean flow characteristics,

averaged autocorrelations, and correspondin g integral length scales.

The correlation analysis will be presented in Section 6.0 and the

integral length scales for all horizontal com p onents and directions are

presented ir, Section 7.0.

The location of the two regions of interest where extensive analysis was

performed is as follows:

San Gorgonio Pass: 14,000 to 21,000 meters N

11,000 to 21,000 meters E

Palm Springs: 6,800 to 13,000 meters N

13,900 to 24,300 meters E
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33

The above regions are defined with respect to a reference location with a

latitude of 330 45' and a longitude of 116 045'. The mean flow characteristics

ana standard deviation are summarized in Tables 3 and 4 respectively.

General flow observations indicate that the flow exiting from the pass

has a higher velocity than the flow over Palm Springs. The lower flow

velocities over the Palm Springs re q ion relative to the flow velocities in the

pass are expected (from continuity) as a result of the diverging cross

j sectional flow area at the exit of the pass.

On the central to north side of the pass the flow tends to exit almost

due east while the flow direction over Palm Springs is 37 0 and 22 0 south of 'I east for runs 13 and 14 respectively. The flow measurements were taken

between 650 and 800 meters above g rades, which are at higher elevations than

the detailed flow/turbulence measurements of previous investiqations (2, 5, 6,

7). There have of course been aircraft measurements with much poorer

resolution than ti.e ADLS system resolution.

It should be noted that prior to any formal analysis of the data, the

data itself was analyzed for validity. Parameters used to screen the data and

eliminate/reject bad points were pulse amplitude, velocity width (doppler

spread), pulse noise level (pulse sigma value), line of sight velocity and the

north and east velocity components.

In order for a data point to be accepted it had to meet the followinq

final screening criteria:

sigma > 1.0

amplitude 126 db

width < 6 m/s

IVLOSI < 3U m/s
=.

34

TABLE 3. MEAN FLOW RESULTS FOR RUN 13 AND 14

(Over Pam Springs and San Gorgoni o ass

Run 13 Run 13 Run 14 Run 14

Palm Springs Pass Data Palm Springs Pass

Data

Mean Flow Angle -.65 -.23 -.37 0.17

(radians with

respect to east)

Mean Longitude 6.91 12.8 7.83 9.53

Velocity (m/s)

Mean Lateral -.41 -.30 -.47 -.63

Velocity (m/s)

Mean Altitude 709 198 643 803

(m)

Mean Amplitude 141 143 141 141

(db)

Mean Sigma Value 0.221 0.164 0.243 0.264

(m/s)

Mean Velocity 1.71 1.76 1.80 1.44

Width (m/s)

Mean Velocity 7.2 13.2 8.4 10.1

Magnitude (m/s)

1 01
35

TABLE 4. STANDARD DEVIATIONS OF FLOW RESULTS FOR RUN 13 AND 14

(Over Palm Sprinqs and San Gorqonio ass

Run 13 Run 13 Run 14 Run 14

Palm Springs Pass Data Palm Springs Pass

^ Data

I

Flow Angle 0.38 0.22 0.48 0.34

(radians with

respect to east)

Longitudinal Flow 3.23 3.08 4.47 2.86

Velocity (m/s)

Lateral Flow 1.93 2.67 2.82 3.53

Velocity (m/s)

Flow Altitude 26.5 51.0 31.0 87.9

(m)

Flow Amplitude 6.83 5.45 6.49 5.01

(db)

Sigma Value 0.23 0.18 0.23 0.24

(m/s)

Velocity Width 0.39 0.42 0.52 0.36

(Spread)(m/s)

Flow Velocity 3.11 3.04 4.28 3.17 

Magnitude (m/s)
36

5.2 Ground Truth Data

The bulk of the ground truth data on which detailed aoalysis was

performed was obtained from the 50 meter Department of Energy meteorological

tower located just north and east of the San Gorgonio pass exit, near the

Southern California Edison Utility's Devers Substation. Other oround truth

data was taken at a Southern California Edison 100 m tower located in the pass

where hourly wind speeds from the 10 meter and 100 meter levels were provided

by Aerovironment, Inc. under contract to the Southern California Edison

Utility.

Additional ground truth data was obtained from three 5 meter towers and

three tala kite anemometers at a height of 100 meters. This oround truth data

was collected on July 10, when the first ADLS tests were performed. Since

little ground truth data was taken on July 29 when the best ADLS data was

collected, the July 10 ground truth data was used to develop the turbulence

and mean wind profiles expected under synoptic conditions similar to the July

10 synoptic conditions. The synoptic conditions for July 29 were virtually

identical to those of July 10 and thus scalin g laws developed from the July 10

data were felt to be valid for the July 29 test.

The vertical variation of wind speed may be represented by coefficient,

a, in the well known power law relation:

CL

U1

Z1

2 22

 ( where V i is the velocity at a height above grade of Zi.

Tht following table represents the power law coefficients obtained at

various locations as a function of time of day.

A; can be seen from the data, the power law coefficient is lar g er near

the ground and decreases with altitude. This is attributed to the flow not

being a fully developed boundary layer flow but rather dominated by the

influence of the acceleration through the pass. Thus upper air velocities,

until the accelerated flow depth is reached, are not expected to greatly

exceed those observed at the 100 meter level. This is consistent with the

results obtained by the ADLS.
37

TABLE 5. SUMMAR'^ Or POWER LAW COEFFICIENTS (a)

50m loom Tala

Time Tower Tower Kite

1500-1600 0.11 0.08 --

1529-1538 -0.01

1555-1605 0.06

1600-1700 0.13 0.11

1625-1635 0.04

1655-1705 0.07

1725-1735 0.06
I

d

it

M

38

The measurements from DOE 50m tower were used for detailed analysis of

near surface data. Specifically the detailed ground truth was used to

estimate the turbulence levels that would be observed 'if an investi g ator were

able to measure the spatial variations in a length of atmosphere similar to

the focal volume of the ADLS. This was accomplished by using Taylor's

hypothesis for changing a time history to a space history. That is, by

multiplying a time history by the mean wind speed such that a particular

quantity is related to a specific distance rather than a specific time (i.e.,

X = ut). It was most convenient to compute temporal statistics for specific

time intervals and relate them to the spatial interval through Taylor's

hypothesis. This data is presented in Table 6.

The data shows that a u decreases with elevation and increase: with

sampling length. Both of these items are as expected. The a u decreases with

elevation due to the fact that dissipation is occurring as the turbulence

moves away from the boundary as well as the fact that the turbulence integral

scale increases away from the boundary thereoy shifting the frequency spectrum

to the left. That is, there becomes less energy available in the spectral

region measured by the spatial or temporal record.

This data tends to bound the turbulence data expected to be observed in

the ADLS data. That is, values of a u

in excess of 1.5 m/s would be highly

suspect. Also Turbulent intensities above about 0.1 would also be highly

suspect. Aoditional data concerning the frequency distributions of the

individual statistics are available from the authors by request.

The synoptic weather patterns for July 10 and July 29 were compared and

showed surprising similarity.

The predominant factor that causes strong, persistent win g s in the San

Gorgonio Pass area during this time of year is the pressure gradient

established across the pass due to cool marine air Penetrating from the west

and the warm air over the Mojave desert. On synoptic weather charts, the data

density is too sparse to show the existence of the pressure gradient in any

detail. However, the surface charts do indicate when this condition can exist

by the presence of a strong Pacific Maritime high pressure system to the west

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40

.f of the region, and a well-developed thermal low pressure system to the east of

s, the region. Such a condition existed on July 10, as car be seen from surface

weather charts on this day. Three hourly of charts, beginning with 0400 PDT

(1200Z) on July 1U, shows a well-developed high pressure system several

hundred miles to the northwest of the region, and a closed thermal low

t immediately to the east of the region. During the time ut the flight,

(approximately 1530-1630 PDT), the pressure gradient across the region dropped

from 1012 mb in Los Angeles to 1005 mb in the desert to the east of San

Gorgonio, as can be seen on a OOOOZ, July 11, surface chart. Since the San

Gorgonio mountain range provides a physical barrier to the two air masses, it

can be anticipated that this is the approximate pressure gradient that existed

across the pass on that day.

Similar synoptic conditions existed on July 29. Although the center of

the Pacific high pressure system is further to the north and east. The

thermal low is equally well developed as it was on the 10th, as a result: the

pressure gradient during the time of maximum heating (1700 PDT) was equivalent

to the 10th dropping irom 1012 mb in Los Angeles to 1004 mb in the desert.

The upper air charts should also provide an indication of the similarity

between the two period, since the semi-permanent Pacific high pressure system

shows as a ridge aloft. However, in the southwestern U.S., during the summer,

upper air charts normally exhibit weak gradients. During this time the region

is relatively free of synoptic-scale disturbances, and temperature differences

are generated primarily by surface heating and cooling patterns, which are not

reflected very strongly in upper level charts. As a result, upper level winds

are generally quite light in this region during this time of year.

The 85U mb charts for July 10 indicate the weak upper-level flow

conditions in the San Gorgonio region. Winds are quite light at Los Angeles,

and temperature and height gradients are very weak. Temperatures at this

height are about 23 0C. The height of this pressure surface is about 1515 m in

this region. A weak west-to-east crad'ent is evident associated with the

Pacific high pressure system centered about 1500 miles to the northwest, and

the thermal low centered over northern Mexico. In the afternoon, this

gradient tightens ind winds increase due to increased surface heating on the
41

east side of the pass. The same pattern prevailed on the 29th, only with a

stronger temperature gradient evident to the north of the re g ion associated

with a large upper-level low pressure system passing across the Pacific

Northwest. However, over the po5s, temperatures and heights of the pressure

level are nearly iden^ical to the 10th, with a qeneral west-east pressure

gradient associated with a Pacific high pressure 2000 miles to the northwest,

and a thermal low pressure over central Mexico.

Examination of the 500 mb charts reveals the synoptic conditions that

prevailed over the northern hemisphere for these two time periods. Ine :w0 mb

charts for these days showed that the synoptic situation for the two periods

was very similar. In both cases a low pressure trou g h existed over the

Pacific Northwest, with temperatures at this prtssurc level around -20 0 C, and

heights of the pressurE level around 5700 m. Over the Pacific Southwest,

temperatures on both days we r e about -5 0C, and heigr.ts of the pressure level

about 5900 m. As with the other charts, the ridge of high pressure over the

Pacific Ocean appears to be somewhat closer to the mainland on the 10th than

on the 29th. In addition, despite similar height g radients, winds at the 500

mb level on the 10th are much stronger, and from the southwest, than on the

29th where winds at Los Angeles were li g ht and from the north.

In summary, examination of the surface and upper air charts for the two

study periods, July 10 and July 29, show that synoptic conditions were ouite

similar for the two days. The Pacific high pressure system was centered

closer to the coastline on the 10th than on the 29th, resulting in slightly

stronger synoptic flow on the 10th. This could be reflected at San Gorgonio

Pass by higher afternoon winds on the 1Cth than on the 29th, although the

synoptic pattern supports stronq thermal gradient winds across the pass for

both periods.

K
42

k'

6.0 CORRELATION ANALYSIS AND RESULTS

The same regions which were analyzed for the detailed wind vector

1 t analysis (Section 5.0) were uses to compute auto- correlations for the lateral

and longitudinal wind components. These correlations were then used to

evaluate integral length scales. To compute the auto-correlations, the

longitudinal and lateral flow directions were evaluated as a spatial average

over the region of interest. Velocity components and *_tieir respective

coordinates were rotated to a coordinate system such that the mean flow

direction became the "X" axis or the longitudinal axis and the normal to the

mean flow direction became the axis or the lateral axis. The

computational procedure used to obtain the average autocorrelations from the

flew field velocity components is discussed below and illustra'ed i.-i Fiqure

9.

Each wind vector then was separated into its longitudinal and lateral

component. The flow region of interest was then divided into 100 meter wide

strips normal to the mean flow direction for lateral direction computations

(i.e., lateral component- lateral direction and longitudinal component-lateral

direction) and 100 meter wiae strips parallel to the mean flow direction for

longitudinal direction computations (i.e., longitudinal component-longitudinal

direction and lateral component-longitudinal direction). The velocity data in

each 100 meter wide strip are then interpolated using a cubic spline to

provide uniformly spaced velocity data needed to perform the correlation

computations. These correlations are then ensemble averaged over the region

of interest producing a true spatial averaged correlation at these upper air

levels.

These average auto correlations from flow over Palm Springs and the flow

exiting the of San Gorgonio Pass are shown in Figures 10 to 25.

Figures 10, 11, 18, 19, 22, and 23 are computed autocorrelations for

velocity components correlated in their component direction (e.g.,

longitudinal component - longitudinal direction). From the Fourier Integral

for the autocorrel,,,,ion of a velocity component in the direction of the

-
W.

43

•; l

e

°° ikX

component R i (X) i _ AiW e i dk, and continuity one can show that with an

infinite record the auto correlation should remain positive. However, for a

finite record where the mean is ramoved from the data (as it is for

correlation/covariance computation) the average value of the auto correlation

may be written as:

X X

X 

f 

R(X)dX = X A(k) cos U dX

k=1

which may be shown to be equa. to zero when integrated over the total

correlation lag X. This i:; hecat^e only finite harmonics remain whose

corre.ations are harmonics of prec ; -ely the same wavenumber and thus each

harmonic integrates to s value o` zero ever the spatial record length. Thus,

for finite record lengths the integral of the correlation must equal zero if

integrated to the record le-. ,:^. An identical analogy exists for temporal

data. Thus, the negativE. pocti,n of the auto correlation for the correlation

of in line components using a finite record length is a necessity. The only

major problem this poles is how to determ;ne the Taylor integral length scale.

The author's of this paper opted for computing the integral scale by

integrating to the first zero, as will be discussed in the next section.

The interpretation of the correlations presented in Figures 10 to 25 do

reveal some interest i ng observations. These are that in the pass region where

the flow is dilitating there is little difference between in line component

correlations and the correlations of components normal to their vector

direction. This shows that the flow in region may not be considered

isotropic. The correlations over Palm Springs appear more normal but still do

not indicate isotropic flow. Longitudinal and lateral spatial correlations

developed for isotropic turbulence using the Van Karmon, Kaimal or Dryden

Spectrum indicate more radical differences in the longitudinal and lateral

correlations that were observed near San Gorgonio.
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61

7.0 ATMOSPHERIC LENGTH SCALES

The autocorrelations provided in Section 6 were used to compute integral

length scales for the flow measured over Palm Springs and at the San Gorgonio

Pass exit. Thee length scales were computed by integrating the

autocorrelation functions to their first crossing. The integral length scale

was first introduced by G. I. laylor (3) in his classical paper on "The

Spectrum of Turbulence". If one examines the relations between correlation

and spectra

b

R(X) = A(k)eikxdk

and - m

A M = y 1 R(X)e-ikxdx

one sees th;, t the integral length scale is simply 27r times the spectral

amplitude at a wavenumber = 0.

Table 7 lists the integral length scales computed from the

autocorrelations given in Section 6. Table 7 also g ,*ves estimated values of

integral scales from various guideline reference documents.

i

E:
62

4

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r1-1

63

LITERATURE CITED

1. H. Yeh, and H. Z. Cummins; Localized fluid flow measurements with He-Ne

laser spectrometer. Appl. Phys. lett. 4,176,1964

2. J. Bilbro, G. Fichtl, D. Fitzjarrald, M. Krause and R. Lee; Airborne

Doppler Lidar Wind Field Measurements; Bulletin of the American

Meteorological Society, Vol. 65, No. 4, April 1984.

3. G. I. Taylor; The Spectrum of Turbulence, Proceedin g s of the Royal

S , x iety, A, Vol. CLXIV (1938), pp. 476-490.

4. J. W. Bilbro and William W. Vaughan; Bulletin of the American

Meteorological Society, Vol. 59, No. 9, September 1978.

5. J. Counihan; "Adiabatic Atmospheric Boundary Layers: A Review and

Analysis of Data From the Period 1880-1972; Atmospheric Environment; Vol.

9, pp. 871-905, 1975, Great Britian.

6. "Characteristics of Atmospheric Turbulence Near the Ground - Part II:

Single Point Data for Strang Winds (Neutral Atmospheric)". Engineering

Science Data Unit, Item No. 74031, March 1975.

7. "Characteristics of Atmospheric Turbulence near the Ground - Part III:

Variations in Space and Time for Strong Winds (Neutral Atmospheric).

Engineering Science Data Unit, Item No. 75001, October 1976.

8. "Terrestrial Environmental (Climactic) Criteria Guidelines for Use in

Aerospace Vehicle Development", 1982 Revision, NASA TM 82473, Robert E.

Turner and C. Kelly Hill, Compliers, June 1982.

9. R. W. Hornbeck, Numerical Methods, Quantum Publishers, Inc. New York,

1975.

k 
64

APPENDIX A

TEST PLAN FOR

NASA'S AIRBORNE DOPPLER LIDAR SYSTEM (ADLS) TESTING

IN SAN GORGONIO PASS AREA

TuTDmirTinu

During FY81, NASA/MSFC elected to perform a flight test option called

"The San Gorgonio Test Option". For this test option the NASA will use its

airborne Doppler Lidar System to characterize the accelerated flow region in

ana near San Gorgonio Pass, California. At this region the maritime layer

from the west coast to accelerated through the pass and then spreads out over

the valley floor on the east side of the pass. The experiment was selected in

order to study accelerate(, flow in and at the exit of the canyon. The test

will also provide information on the atmospheric flow in this region for which

J DOE, Southern California Edison, and the State of California have expressed

h

interest from wind energy resource considerations.

The NASA ADLS is pulsed and has a spatial resolution of about 300 m and

will average over 140 contiguous beam paths for each range gate to a ran q e of

1U km. This system measures the along-line-of-site wind velocity component.

Ground truth will be available for limited comparison with the NASA ADLS

results. The ground truth will include wind data taken, concurrently with the

flight data, by

a) one 100 m (330 ft) tower, 4 levels of instrumentation (Data will be

taken courtesy of Southern California Edison by Aerovironment

personnel.)

b) one 50 m (160 ft) tower, 3 levels of information (Dan will be taken

for DOE by PNL.)

c) approximately ten meter (33 ft) towers, one level of instrumentation

(Data will be taken courtesy of Southe r n California Edison by

Aerovironment personnel.)

d) three tala kites (Data will be taken courtesy of Southern California

Edison by Aerov-;-onment personnel.)
65

G

The NASA aircraft must have an air-to-ground communication System so that

the flight paths, times, etc., can be continuously communicated to the

Southern California Edison, Aerovironment, and PNL personnel taking the around

truth data.

t

Personnel tentatively identified to coordinate the various ground truth

activities are

PNL--Dave Renne or Tom Heister (509) 375-6161

Battelle--William Cliff (509) 3-15-2024

Southern Cal. Edison--Robert Yinger (213) 572-2196

Aerovironment--Tom Zambrano (213) 449-4329

It is expected that Battelle, PNL, and Southern California Edison will

have representatives on board the aircraft during the flight testing. These

personnel will require ground communication to their in-the-field personnel.
66

FLIGHT PATHS FOR NASA

AIRBORNE DOPPLER LIDAR SYSTEM

r „ The following flight paths have been designed to obtain information of

the flow at the exit of San Gorgonio Pass and flow throu g h the pass. These

L flight paths have also been designed to obtain information which may be

compared with data obtained at the ground stations previously described.

Flight Path No. 1

Beam Configuration: Locked, looking forward and down

Axmuthal angle of beam, A A (top view) = 13.840

Elevation angle of beam, 9 E (front view) = 15.1)00

Vertical angle of beam, 9 Z (side v?ew ins; 2 plane) = 47.410

Flight Path: South to north along constant lon g itude of 116 0 34'43"W (along

1 section line which bisects sections 20 and 21 in Township 3S and

! Range 4E)

! Starting at Latitude: 33051'35"N

Ending at Latitude: 33058'30"N

Altitude of flight path: 7620 ft above sea level

This flight path is 4.8 miles from the Southern California Edison 100 meter

tower. The beam will intercept the ground at the tower, thus permitting

comparison with the tower measurements. This flight path will also provide

data on the vertical profile of the horizontal velocity field. In this

configuration each unit length of the laser beam will have a northerly

component of 0.23147, a westerly component of 0.93969, and a vertical

component of -1.25179.

Flight Path No. 2, 3, and 4

Beam Configuration: Same as Flight Path No. 1

Flight Path: South to north along a constant longitude of 116032'41"

(directly along Indian Avenue, bisecting Sections 22 and 23 in

Township 3S and Range 40

rig
67

i

r

Starting Latitude: 33050'44"N

Ending Latitude: 33058'30"N

(Starting on the ;.itersections of Sections 1U, 11, 14 and 15 of

Township 4S and Range 4E, and endin g on the intersection of

Sections 22, 23, 26 and 27 of Township 2S and Range 4E)

Altitude of Flight Path:

No. 1: 3760 ft above sea level

(This is about 3000 ft above North Palm Springs)

No. 2: 426;) ft above sea level

No. 3: 5760 ft above sea level

This flight path is 2 miles from the DOE tower and Southern California wind

turbine area. These flights should help define the verticel profile in the

region where the valley opens up.

Flight Paths No. 5, 6, 7, 8, 9, 10, and 11

Beam Configuration: Nominal horizontal scan

Flight Path: South to north on odd number flight paths and north to south on

even number flight paths

All flights along constant longitude of 116034'43"W

(Same as flight path No. 1)

Starting Latitude: 33051'35"?:

Ending Latitude: 33058'3)"N

(Latitudes same as Flight Oath No. 1)

Altitude of Flight Paths:

No. 5: 25UU ft above seal level

(about 1SOO ft above terrain)

No. 6: 25UO ft above sea level

No. 7: 3000 ft above sea level

No. 8: 35UU ft above sea level

No. 9: 3500 ft above sea level

No. IU: 6000 ft above sea level

No. ;1: 6000 ft above seal level
68

These flights are to describe the horizontal flow field near and outside the

exit of the pas;.

Flight Paths No. 12, 13, 14, 15, 16, and 17

Beam Configuration: Nominal horizontal scan

Flight Path: East to west on even numbered flights and west to east on odd

numberea flights.

Even numbered flights the p',ane should stay 112 mile north of

Interstate 10 beginning where Interstate 10 crosses flight path

No. 2 (Longitude 116 0 32'41") and proceed west co Banning. Odd

numbered flights should stay 1/2 mile south of Interstate 10

beginning at Banning and proceeding east to where Interstate 10

crosses flight path No. 2.

All flight paths are to be slanted such that the plane stays a

constant height above grade.

Height above grade for flight path:

No. 12 1500

No. 13 1500

No. 14 2500

No. 15 2500

No. 16 5000

No. 17 5000

These flight paths will be approximately 18 miles long an'.1 will define the

horizontal wind field, its velocity and direction as it f'ows down the pass.

It wil l also assist in defining the depth of the maritime layer taar Banning.