11/20/2002 - 1

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ACLAIM CAMEX-4 Backscatter and Wind Velocity Measurements – Ivan Clark (Co-I) NASA LaRC

Objectives-Operational experience at cruise speed and altitude with:

-eye-safe Lidar-high moisture environment-large backscatter variations-variety of clouds, clear-air and very clean air-cloud entry and exit

-Evaluate range of detection for light to moderate turbulence-Validate Lidar wind shear measurement capability-Validate atmosphere backscatter design model-Demonstrate clear-air turbulence (CAT) detection and prediction

NASA DFRC: Ed Teets (PI), Jack Ehernberger (Co-I) Rod Bogue (Co-I);(AS&M) Chris Ashburn

CTI: Philip Gatt (Co-I), Sara Tucker & Dale Bruns

NASA LaRC: Gary Grew, Phil BrockmanWayne Gerdes; (Swales) Carroll Rowland

ACLAIM periscopeACLAIM periscope

11/20/2002 - 2

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Doppler Radar/Lidar Turbulence Measurement General Principle

updraft

downdraft

DopplerTurbulence Sensor

Pulse transmitted Energy scattered off of naturally-occurring moisture or aerosols

Relative wind induces a Doppler frequency shift in the backscattered light; this frequency

shift is detected by the sensor

Lidar Pulse Envelope (50-100 meters)Radar Pulse Envelope (~300 meters)

Lidar“Pencil” BeamWidth 10-20 cm

Beam

Rel

ativ

e A

irspe

ed

Distance or Time Ahead of Aircraft

TurbulenceRadar BeamSpread 3.5°

11/20/2002 - 3

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Atmospheric Aerosol Backscatter for Clear Air:Previous Database and CAMEX-4 ACLAIM Database

2.096 um Backscatter Database

10-10 10-9 10-8 10-7 10-6

Backscatter Coefficient (m-1sr-1)

0

2

4

6

8

10

12

14

AG

L A

ltitu

de (k

m)

Extinction & Turbulence CorrectedUS, Northern with out Clouds

Resolution = 92.5 m

10% CDF50% CDF90% CDFSensitivityModels

10−10

10−9

10−8

10−7

10−6

0

2

4

6

8

10

12

Backscatter Coefficient (m−1sr−1)

MS

L A

ltitu

de (k

m)

2 µm Backscatter Coefficient

Ground Based 90%Ground Based 50%Ground Based 10%ACLAIM 90%ACLAIM 50%ACLAIM 10%

•CAMEX-4 ACLAIM database

•Forward-looking, clear-air only

•3600 discrete samples of 5 seconds each

•Consistent with ground-based measurements

•Ground database collected 1995-96 in continental US

•High altitude 50% profile derived from 1.06m GLOBE measurements

11/20/2002 - 4

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ACLAIM vs Dropsonde Radial VelocitySeptember 10, 2001 Comparison

11/20/2002 - 5

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Lidar Atmospheric Sensing Experiment (LASE) vs ACLAIMSeptember 10, 2001 Comparison

11/20/2002 - 6

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CAMEX-4 Analyses Status

•CAMEX-4 flights very helpful to AvSP Turbulence Lidar effort

•ACLAIM forward-looking velocity and backscatter initial analysis done

•Quick look qualitative comparison of LASE and ACLAIM very promising

•ACLAIM up-slope line-of-sight data analysis underway for vertical windshear

•ACLAIM CAMEX-4 data and experience very helpful for evaluation of beam quality, data acquisition and archiving procedures, and 2-micron lidar doppler behavior in convectively-induced turbulence

•ACLAIM up-slope line-of-sight configuration could support a wind shear measurement inter-comparison between rawinsondes, ICATS climb winds, and both DC-8 and ER-2 dropsonde wind profiles on a future mission