S. Tucker 1,2 , I. Dors 3 , R. Michael Hardesty 1 , and Wm. Alan Brewer 1

Preliminary comparison results of the October 2003 experiment with GroundWinds NH and

NOAA's mini-MOPA lidar

S. Tucker1,2, I. Dors3, R. Michael Hardesty1, andWm. Alan Brewer1

Acknowledgements: A. Weickmann1,2 and M. J. Post4

¹Optical Remote Sensing GroupChemical Sciences Division (CSD)Earth System Research Laboratory

http://www.etl.noaa.gov/et2

²Cooperative Institute for Research in Environmental ScienceUniversity of Colorado, Boulder, CO

³University of New Hampshire, 4Zel Technologies, LLC/NOAA,

Working Group on Space-Based Lidar Winds Key West, FL, January 17-20, 2005

October 2003 Field Experiment• NOAA’s mini-MOPA Coherent DWL• GroundWinds New Hampshire DWL• Occasional balloon-sonde launches

NOAA’s 2005 Comparison and Validation ObjectivesUse analysis and comparisons to mini-MOPA data to:

• Verify GWNH performance

– Ability to accurately measure wind profiles

– Precision & accuracy (in stares and profiles)

• Check for improvements over GWNH 2000 data

• Verify photon count – extend to technological scaling to space.

• Quantify sensitivity improvements due to Photon Recycling

Additional Activities: Mini-MOPA Analysis

Take advantage of long stare times in windy climate to study:– Sensitivity versus theoretical limit of the instrument – Effect of pulse duration on sensitivity – Extraction of mini-MOPA data at low SNR in the free

troposphere– Pulse modeling– Turbulence profiling

Velocity Variance Estimation Methods

• Zeroth lag estimation: Mayor, et. al., J. Atmos. Oceanic Tech, 1997

• Spectral noise floor estimation

0 1 2 3 4 5 6 7 8 9 10

0.08

0.09

0.1

0.11

lags

autocorrelation

Autocovariance function at 1.26 km Range

N lag ACF

linear fit ACF

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

100

Frequency (Hz)

spectral amplitude

Spectrum at 1.26 km range

Spectrum at range2 gate meanfloor

• Brovko-Zrnic Cramer-Rao Lower Bound: Rye & Hardesty, IEEE Trans Geoscience & Remote Sensing,1993.

• UNH method: Standard deviation of 1 minute sliding window (5-6 samples at 10 s averaging times)

Wavelength 9-11 micron

Pulse Energy 1-2 mJ

PRF 300 Hz

Max Range 18 km

ScanningFull

Hemispheric

Precision 10 cm/s

Range Resolution

45-300 m

λ1

λ2

AOM1 AOM2

CW Lasers

Shutters

Pol BS

? wave

Local Oscillator

12 Pass

RF Discharge Optical Amplifiers

6 Pass1/4 wave

8 “ Off Axis Parabolic Telescope

Pol BS

CooledDetector

Mini-MOPA Doppler Lidar

-12 -10 -8 -6 -4 -2 0 2 40

0.2

0.4

0.6

0.8

1

Wide-band SNR (dB)

v (m/s)

MOPA v

vs. wbSNR. GW031025_0336, File 8.

Alt.km

ACF lin fitIdeal CRLB

0 0.5 1 1.5

• CRLB: Rye & Hardesty, IEEE Trans Geoscience & Remote Sensing,1993.

Mini-MOPA: Sensitivity versus theoretical limit of the instrument

• CNR dependent-minimum standard deviation values calculated using the linear fit to 0th lag of the ACF

• Black line: BZ-CRLB for these CNR values• Square fill colors represent altitude according to the colorbar. • Room for improvement?

-12 -10 -8 -6 -4 -2 0 2 40

0.2

0.4

0.6

0.8

1

Wide-band SNR (dB)

v (m/s)

MOPA v

vs. wbSNR. GW031025_0336, File 8.

Alt.km


0 0.5 1 1.5

0 2 4 6 8 100

0.2

0.4

0.6

0.8

1

Lags

MOPA xcov

MOPA 1 s

Gaussian 1 s

AutocovarianceFunction

Mini-MOPA pulses: effect on velocity variance

Pulse Shape

Variable Pulse Width & Accumulation Time

NOAA’s GWNH Validation Activities and mini-MOPA comparisons

• Verify MOPA’s usefulness as a comparison measurement

• Independent estimation of GWNH velocity variance– Range-independent variation removal– Photon-recycling vs. no Photon-recycling

• Comparison between GWNH and NOAA’s mini-MOPA lidar– Comparison of wind measurements – Comparison of turbulence measurements – Characterization of measurement biases – Characterization of systematic effects – Comparison of boundary layer performance

LWG – Key West, FL January 17-20, 2005

Time (min)

Altitude (km)

10/31/03,02:55 MOPA LOS velocity. El:44°

200 205 210 215 220

1

2

3

4

5

6

-25

-20

-15

-10

-5

0

5

10

15

20

25

Mini-MOPA wind profile validation

0 10 20 300

1

2

3

4

5

6MOPA profile:3:27:43

D200310310722.MWO

10/31/03MOPA & Balloon-Sonde

Wind Speed (m/s)

Altitude (km)

BalloonMOPA

250 300 3500

1

2

3

4

5

610/31/03MOPA & Balloon-Sonde

Wind Direction (deg.)

BalloonMOPA

0 10 20 30 40 500

2

4

6

8

10

12

MOPA profile:21:28:07D200311010131.MWO

10/31/2005Wind Speed

Wind Speed (m/s)

Balloon

MOPA

100 200 3000

2

4

6

8

10

12


Altitude (km)

10/31/2005Wind Direction

MOPA profile:21:28:07D200311010131.MWO

Balloon

MOPA

Time (min)

Altitude (km)


1282 1284 1286 1288 1290 1292 12940

2

4

6

8

10

12

Mini-MOPA wind profile validation

Removal of GWNH offsets affecting all range gates (to improve precision estimates)

1. Take signal at each range gate & find linear trend.

2. Remove linear trend – left with variations about that trend.

3. Average the variations (not applicable in cases of strong turbulence)Time (min)

Altitude (km)

10/25/03,05:12 MOPA LOS velocity. El:44.5°. Az:312°

320 330 340 350 360 370

0.5

1

1.5

2

Time of Day (min)

Altitude (km)

GWNH LOS Molecular Velocities (m/s) (PR). NH_20031025051258_M57

320 330 340 350 360 370

0.5

1

1.5

2

Time of Day (min)

Altitude (km)


320 330 340 350 360 370

2

4

6

8

10

record number

range

Velocity Estimate

100 150 200 250 300

5

10

15

-40

-30

-20

-10

0

10

record number

range

Corrected Velocity Estimate

100 150 200 250 300

5

10

15

-40

-30

-20

-10

0

10

record number

range

Velocity Estimate (PR)

100 150 200 250 300

5

10

15

-40

-30

-20

-10

0

10

record number

range

Corrected Velocity Estimate (PR)

100 150 200 250 300

5

10

15

-40

-30

-20

-10

0

10

Effects of NOAA/CSD-correction for instrument offsets

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 150

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

v (m/s)

Altitude (km)

Standard Deviation vs. Altitude NH_20031025051258_M57

CSD-corrected linear fit ACF

Uncorrected - linear fit ACFCSD-corrected Spectral noise floor

Uncorrected - Spectral noise floor

CSD-corrected 1 min std

Uncorrected 1 min std (UNH method).

UNH supplied Meas. Limit

BW/ (NPED)

GW Variance estimates (photon recycled data)

• σv estimates match UNH supplied measurement limit at altitudes above 6.5 km – Instrument/Camera limitations dominate

• Difference between UNH’s measurement limit and photon limit is described in UNH reports.

• sub 6.5 km results –Instrument and camera limitations cease to dominate. Other limitations?

0 0.5 1 1.5 2 2.50

1

2

3

4

5

6

7

8

9

v (m/s)

Altitude (km)


CSD-corrected linear fit ACF

CSD-corrected Spectral noise floor

CSD-corrected 1 min std

Uncorrected - linear fit ACF

Uncorrected - Spectral noise floor

Uncorrected 1 min std.

UNH supplied Meas. Limit

GW Variance estimates post-correction (PR)

• Uncorrected σv estimates: ACF and Spectral methods more optimistic then 1 minute σv estimates.

BW/ (NPED)

• Post-correction σv estimates match UNH supplied measurement limit down to ~ 2km

• Near 2 km altitude errors due to presence of thin clouds.

0.7 0.8 0.9 1 1.1 1.20

2

4

6

8

10

12

14

16

Altitude (km)

Factor change in standard deviation0 0.5 1 1.5 2 2.5 30

1

2

3

4

5

6

7

8

9

10

v (m/s)

Altitude (km)


linear fit 0th lag ACF

linear fit 0th lag ACF PRUNH Meas. Lim

UNH Meas. Lim PR

BW/ (NPED)

BW/ (NPED(PR))

(post-correction) σv Ratios

1/(PED ratio)Spectral noise floor ratio

ACF 0th lag est. ratio

Measurement limit ratio

1 minute v ratio

PHOTON RECYCLING: σv Ratios• Photon count ratios of ~2, ideally correspond to σv

ratios of ~0.71.

• Ratio of Photon Recycling (PR) to non PR σv estimates vary around the ratios of UNH supplied measurement limits (usually 0.75 to 0.9)

• See UNH report regarding PR “quality factor”

0 10 20 300

1

2

3

4

5

6

7

8

GWNH profile:03:40:30MOPA profile:3:27:43

D200310310722.MWO

10/31/03, GWNH with Photon Recycling20031031034030_M110

Wind Speed (m/s)

Altitude (m)

BalloonMOPAGWNH-AGWNH-M

Wind Profile Comparisons

Time of Day (min)

Altitude (km)


230 240 250 260 270 280 290 300 310 320 330

2

4

6

8

Time (min)

Altitude (km)


230 240 250 260 270 280 290 300 310 320 330

2

4

6

8

Time of Day (min)

Altitude (km)

GWNH LOS Aerosol Velocities (m/s) (PR). NH_20031031034030_M11

230 240 250 260 270 280 290 300 310 320 330

2

4

6

8

Wind Profile Comparisons

0 10 20 300

1

2

3

4

5

6

7

8GWNH profile:03:40:30MOPA profile:3:42:44D200310310722.MWO

10/31/03, GWNH with PR20031031034030_M110

Wind Speed (m/s)

Altitude (m)

BalloonMOPAGWNH-A

0 10 20 300

1

2

3

4

5

6

7

8GWNH profile:03:40:30MOPA profile:3:27:43D200310310722.MWO

10/31/03, GWNH with PR20031031034030_M110

Wind Speed (m/s)

Altitude (m)

BalloonMOPAGWNH-A

-5 0 50

1

2

3

4

5

6

7

8

Wind Speed Difference (m/s)

Altitude (m)

20031031034030_M110

GWNH-AGWNH-MGWNH-A-PRGWNH-M-PR

-5 0 50

1

2

3

4

5

6

7

8

Wind Speed Difference (m/s)

Altitude (m)

20031031034030_M110

GWNH-AGWNH-MGWNH-A-PRGWNH-M-PR

Alti

tud

e (

km)

Alti

tud

e (

km)

Alti

tud

e (

km)

-10 -5 0 50

1

2

3

4

5

6

Az =180, GW Time:231.3MOPA profile:231.7

Altitude (km)

Vest (m/s)-5 0 5 10 15 200

1

2

3

4

5

6

Az =225, GW Time:251.6MOPA profile:252

Vest (m/s)0 10 20 30

0

1

2

3

4

5

6


Vest (m/s)0 5 10 15 20 250

1

2

3

4

5

6

Az =315, GW Time:287MOPA profile:286

Vest (m/s)

-10 -5 0 5 100

1

2

3

4

5

6


Altitude (km)

Vest (m/s)-15 -10 -5 0 5 100

1

2

3

4

5

6


Vest (m/s)-20 -10 0 100

1

2

3

4

5

6

Az =90, GW Time:331MOPA profile:323.3

Vest (m/s)

MolecularMolecular PRballoonMOPA projectedMOPA Direct

Single Az. Profile Comparisons for Molecular Channel

Time (min)

Altitude (km)


1065 1070 1075 1080 1085 1090 1095 1100

2

4

6

8

10

12

Time of Day (min)

Altitude (km)


1065 1070 1075 1080 1085 1090 1095 1100

2

4

6

8

10

12

Time of Day (min)

Altitude (km)


1065 1070 1075 1080 1085 1090 1095 1100

2

4

6

8

10

12

Stare Comparisons

-15 -10 -5 0 5 10 150

2

4

6

8

10

12

Velocity Difference (m/s)

Altitude (km)

Difference in Mean LOS Velocity Estimates10/31/03, Minutes: 1088 to 1102

MOPA-MolecularMOPA-AerosolMOPA-Molecular PRMOPA-Aerosol PR

-40 -30 -20 -10 0 100

2

4

6

8

10

12

Mean LOS Velocity (m/s)

Altitude (km)

10/31/03. Mean LOS Velocity EstimatesMinutes: 1088 to 1102

MOPAMolecularAerosolMolecular PRAerosol PR

Time (min)

Altitude (km)


120 125 130 135 140 145 150 155

1

2

3

4

5

6

Time of Day (min)

Altitude (km)


120 125 130 135 140 145 150 155

1

2

3

4

5

6

Time of Day (min)

Altitude (km)


120 125 130 135 140 145 150 155

1

2

3

4

5

6

-10 -5 0 5 100

1

2

3

4

5

6


Altitude (km)



-15 -10 -5 0 5 100

1

2

3

4

5

6


Altitude (km)



Stare Comparisons: Offsets?

Summary

• Mini-MOPA performance is as modeled. MOPA data provides useful comparisons for low-level GW data.

• GWNH wind profiles generally compare well to those of MOPA and balloon-sonde data when clouds are not present.

• GWNH velocity variations approach the measurement limit modeled by UNH, however they are significantly higher than the theoretical detected-photon limit.

• UNH has attributed this degradation in velocity-variation, relative to the photon-limit, to receiver limitations.

• GWNH measurements show variable offsets relative to mini-MOPA and balloon-sonde data.

B. J. Rye, “Estimate optimization parameters for incoherent backscatter heterodyne lidar including unknown signal bandwidth,” Appl. Opt., 39, 6086-6096 (2000).• B. J. Rye, “Comparative precision of distributed backscatter Doppler lidars,” Appl. Opt. 34, 8341-8344 (1995).• R. Frehlich, “Estimation of Velocity Error for Doppler Lidar Measurements,” J. Atmos. Oceanic. Tech, 18, 2001, 1628-1639.• D. H. Lenschow, V. Wulfmeyer, and C. Senff, “Measuring Second- through Fourth-order Moments in Noisy Data,” J. of Atmos. Ocean. Tech., 17, 1330-1347, (2000).• S. D. Mayor, D. H. Lenschow, R. L. Schwiesow, J. Mann, C. L. Frush, and M. K. Simon, “Validation of NCAR 10.6-m CO2 Doppler Lidar Radial Velocity Measurements and Comparison with a 915-MHz Profiler,” J. Atmos. Oceanic Tech., 14, 1997, 1110-1126.• B. J. Rye, R. M. Hardesty, “Discrete Spectral Peak Estimation in Incoherent Backscatter Heterodyne Lidar. I: Spectral Accumulation and the Cramer-Rao Lower Bound,” IEEE Trans Geoscience & Remote Sensing, 31, 1993, pp 16-27.

Assorted References


miscellaneous

Time (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

Time of Day (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

Time of Day (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

Stare Comparisons: Boundary Layer

-10 0 100

0.5

1

1.5

2

2.5

3

3.5

4


Altitude (km)



-30 -20 -10 0 100

0.5

1

1.5

2

2.5

3

3.5

4


Altitude (km)



-10 0 100

0.5

1

1.5

2

2.5

3

3.5

4


Altitude (km)



Time (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

Time of Day (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

Time of Day (min)

Altitude (km)


980 985 990 995 1000 1005 1010 1015 1020 1025 1030

1

2

3

4

-30 -20 -10 0 100

0.5

1

1.5

2

2.5

3

3.5

4


Altitude (km)



Stare Comparisons: Boundary Layer

-10 -5 0 50

1

2

3

4

5

6


Altitude (km)

HVest (m/s)-5 0 5 10 15 200

1

2

3

4

5

6


Vest (m/s)0 10 20 30

0

1

2

3

4

5

6


Vest (m/s)0 5 10 15 20 250

1

2

3

4

5

6

Az =315, GW Time:287MOPA profile:286

Vest (m/s)

-10 -5 0 5 100

1

2

3

4

5

6


Altitude (km)

Vest (m/s)-15 -10 -5 0 5 100

1

2

3

4

5

6


Vest (m/s)-20 -10 0 100

1

2

3

4

5

6

Az =90, GW Time:331MOPA profile:323.3

Vest (m/s)

AerosolAerosol PRballoonMOPA projectedMOPA Direct

Single Az. Profile Comparisons for Aerosol Channel

0 5 10 15 20 25 300

1

2

3

4

5

6

7

8


D200310310722.MWO

10/31/03, GWNH without Photon Recycling20031031034030_M110

Wind Speed (m/s)

Altitude (m)


0 5 10 15 20 25 300

1

2

3

4

5

6

7

8


D200310310722.MWO


Wind Speed (m/s)

Altitude (m)


240 260 280 300 320 3400

1

2

3

4

5

6

7

8

10/31/03, GWNH without Photon Recycling20031031034030_M110



D200310310722.MWO


240 260 280 300 320 3400

1

2

3

4

5

6

7

8




D200310310722.MWO


GWNH Validation Activities

GroundWinds– Sensitivity versus theoretical limit of the instrument for

NH and HA systems– Sensitivity improvements made at GWNH since the

LidarFest. – Total system transmission and recycling efficiencies – Technological scaling to potential airborne and space

systems – Comparison of performance between the New

Hampshire and Hawaii systems


Distribution of (post-correction) σv Ratios

0.65 0.67 0.69 0.71 0.73 0.75 0.77 0.79 0.81 0.83 0.85 0.87 0.89 0.91 0.93 0.95 0.97 0.99 1.01 1.03 1.050

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

PR to non-PR ratio

Percentage

Spectral noise floor v ratio

ACF 0th lag est. v ratio

Measurement limit ratio1 minute v ratio

1/√(PED ratio)

0.65 0.67 0.69 0.71 0.73 0.75 0.77 0.79 0.81 0.83 0.85 0.87 0.89 0.91 0.93 0.95 0.97 0.99 1.01 1.03 1.050

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

PR to non-PR ratio

Percentage

Spectral noise floor v ratio

ACF 0th lag est. v ratio

Measurement limit ratio1 minute v ratio

1/√(PED ratio)

Distribution of (no correction) σv Ratios

Decreasing Pulse Width: Increased velocity variance & offset

0.2 0.4 0.6 0.8 1-15

-10

-5

0

Velocity Estimate (m/s)

Pulse Width (s)

Inconsistent CRLB fits and velocity offsets led to further investigation of the MOPA pulse formation process…

Mini-MOPA Pulse Formation: Block Diagram

CW CO2 Laser

RF Discharge Optical Amplifiers

ω0AOM1

+54 MHz

12 Pass

H(ω)

output from AOMs

FFT

6 Pass

H(ω)

AOM2

-44 MHz

FF

T

output from amplifiers

3.2068 3.2068 3.2069 3.2069

x 1013

0

0.5

1

1.5

Lorentzian Gain, |H(ω)|

frequency

normalized gain

3.2068 3.2068 3.2069 3.2069

x 1013

-20

0

20

Lorentzian Phase

frequency

normalized phase

Line centerPulse center

( ) ( ) ( )( ) ( )22

0

2

02

2

υυυ

υυγυγ

Δ+−

Δ=

( ) ( )υυυ

υγυϕΔ−

= 0

Mini-MOPA pulse modeling

Exaggerated examples of asymmetric effect on velocity estimates

0

0.2

0.4

0.6

0.8

1

frequency

Normalized Amplitude

1 μs pulseΔf=0.1Mhz=-0.5m/s

0

0.2

0.4

0.6

0.8

1

frequency


500 ns pulse

0

0.2

0.4

0.6

0.8

1

frequency


500 ns pulseΔf=0.55Mhz=-2.5m/s

0

0.2

0.4

0.6

0.8

1

frequency


1 μs pulse

10 MHz

0.2 0.4 0.6 0.8 1-15

-10

-5

0


Pulse Width (s)

-12 -10 -8 -6 -4 -2 0 2 40

0.2

0.4

0.6

0.8

1

Wide-band SNR (dB)

v (m/s)

MOPA v

vs. wbSNR. GW031025_0336, File 8.

Alt.km


0 0.5 1 1.5

-10 -5 0 5 10 15 200

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

CNR (dB)

CRLB

MOPA 1 sGaussian 1 sMOPA 500 nsGaussian 500 ns

0 2 4 6 8 100

0.2

0.4

0.6

0.8

1

Lags

MOPA xcov

MOPA 1 sGaussian 1 sMOPA 500 nsGaussian 500 ns

Model with pulses at 10 MHz off amplifier line-

center

ACF CRLB

Mini-MOPA pulses: effect on velocity variance

Mini-MOPA: Velocity Offset vs. Pulse Width

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-6

-5

-4

-3

-2

-1

0

Pulse Width (μs)


range (km) 60 m pulse, vertical stare velocity estimates

1

2

3

-2

-1

0

1

2

Average frequency monitor velocity estimate vs. pulse

width

Documents

S. Tucker 1,2 , I. Dors 3 , R. Michael Hardesty 1 , and Wm. Alan Brewer 1