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Airborne Doppler wind lidar: typhoon research and long flight-

leg data sets for data impact studies related to a future space-

based Doppler wind lidarGeorge D. Emmitt, Simpson Weather Associates, Inc. (United

States); Ralph Foster, Univ. of Washington (United States); Daniel Eleuterio, Naval Research Lab. (United States)

Lidar Remote Sensing for Environmental Monitoring IXNew Caledonia

18 November, 2008

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OverviewAn airborne Doppler wind lidar (1.6 micron coherent) was

flown on a Navy P3 in ONR/NSF typhoon research missions during August/October 2008.

In addition to full vector wind profiles in clear and partly cloudy conditions, a primary research target unique to the Doppler lidar will be the Organized Large Eddies (OLE) that are theorized to have significant impacts on air sea fluxes controlling the evolution of tropical cyclones.

Measurements of the vertical velocity of the water surface allows wave spectra to be computed.

Efforts are underway to process and subset the thousands of lidar wind profiles taken to simulate the coverage expected from a future space-based DWLs such as GWOS and NWOS.

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Outline

• Overview of the P3DWL activity in TPARC/TCS08– Wind profiles to augment dropsondes– Prospecting for OLEs as major air/sea interaction

factor in developing TCs– MBL aerosol structures and wave spectra

• Example of P3DWL data from Typhoon Nuri flights• Examples of DWL data for OLEs• Examples of DWL data for extracting wave data

T-PARC: THORPEX Pacific Asian Regional Campaign; TCS-08: Tropical Cyclone Study 2008

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P3DWL for TPARC/TCS-08

1.6 um coherent WTX (ARL/LMCT)10 cm bi-axis scanner (NASA)P3 and other parts (NRL)Analyses software (SWA/CIRPAS)

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The instrument

• 1.6µm coherent detection• 1 mJ• 2000 Hz• 10 cm two axis scanner, side mounted• GUI with realtime instrument control and data

display• Range: 3 – 20 km depending upon aerosols• Weight: <200lb Power: 300 watts

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The MLX-16 coherent Doppler lidar built by LMCT for the US Army (ARL).

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Mission Plan• Study of tropical cyclogenesis, intensification,

transition and weakening• Based out of Guam (P3)• Other aircraft include USAF C130 and DLR Falcon

– P3: dropsondes, ELDORA and P3DWL– C130: dropsondes– Falcon: dropsondes, DWL, DIAL

• Use ferry flights to collect long curtains of wind soundings to test data impact on NWP.– Pax River to West Coast– West Coast to Hawaii– Hawaii to Guam

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Guam

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Activity Summary

• P3DWL in the field from August 4 to October 8, 2008

• Total data (ground and airborne) = 171 hours• Flew 18 missions with Tropical Cyclones as target

– 118 hours of data• Additional flights:

– Calibration of other instruments – Ferry flights between bases– Ferry flights USA – Guam – USA (> 20000 km)

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Example of P3DWL observations near a Typhoon

• Tropical cyclone Nuri• August 16 -17 , 2008 flight• Flight level ~3000 meters• Downward scanning for wind profiles

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Flight level winds from P3

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P3DWL winds at 2100 M

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P3DWL winds at 1500 M

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P3DWL winds at 500 M

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P3DWL winds at 200 M

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00007 UTC Dropsonde: (Three horizontal red lines are at 800, 900, 1000 mb). Wind barbs are 5 m/s full, 2.5 m/s for half barb.

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0 60 120 180 240 300 360W IND D IREC TIO N (DEG )

0

200

400

600

800

1000

1200

1400

1600

1800

2000H

EIG

HT

(M

)

0 2 4 6 8 10 12 14 16 18 20W IND SPEED (M /S)

LIDAR W IND PR O FILEN UR I FLIG HT 1AU G 17, 2008000036 PRO FILE 3BLACK: W IND D IREC TIO NR ED: W IND SPEED

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Dropsonde at 0131, just east of the circulation center:

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0 60 120 180 240 300 360W IND D IREC TIO N (DEG )

0

200

400

600

800

1000

1200

1400

1600

1800

HE

IGH

T (

M)

0 2 4 6 8 10 12 14 16 18 20W IND SPEED (M /S)

LIDAR W IND PR O FILENUR I FLIG HT 1AU G 17, 2008013454 PRO FILE 5BLACK: W IND D IRRED: W IND SPEED

Lidar profile at 013454, number 5. Qualitatively similar to the dropsonde: SSW flow at lowest levels, southerly flow through deep layer shifting towards E at top of profile

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Organized Large Eddies

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~1500m

~400m

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0 2 4 6 8 10

ALO N G FLIG H T-TR ACK D ISTAN C E (KM )

- 2

- 1

0

1

2

VLO

S (

M/S

)

- 2

- 1

0

1

2

SIG

NA

L S

TR

EN

GT

H

M AR C H 12, 2002 T IM E 1448 (100 ')T IM E SER IES FO R G ATE 10 (950 M )VLO S (R ED ), S IG N AL STR EN G TH (BLAC K)

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Water surface returns

• Reasons for water surface returns at >20 degrees include foam, spray and wave tilting of capillary facets

• Using data taken with a nadir viewing angle, vertical wave motions can be used to measure wavelengths.

• Wave tilt is estimated from height and length of wave. Crest angles of 150-170° are common.

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Nadir view over water (single shots)

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TODWL wave measurements with aircraft related corrections

• Ground speed = 55 m/s• Sample frequency 80Hz >> .69 m/sample• Wavelength of swell = 200 m• Wavelength of wind waves = 21.5 m

– max tilt of wave surface ~ 13 degrees

• Maximum vertical wave velocity of 1.9 m/s

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Expected waves

• NOAA Buoy 46042 - Monterey– winds: 19kts from NW– swell: 2.4 meters; 11.1 seconds; NW

• computed wavelength = 192 meters

– wind waves: 1-1.2 meters; 3.7 seconds; NNW• computed wavelength = 21.4 meters

• Tables– 17-21 kts > 1.3 m; 5.4 s; 20-30m length

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Summary

• Wind lidar data taken with a 2 um coherent Doppler wind lidar on board the NRL P3 aircraft is now going through final processing.

• Preliminary inspection of the data suggests that > 85% useful data collected between surface and 3km; this appears to be the case even when observing near TCs.

• Long curtains of wind profiles are available for simulating future space-based DWLs and data impact studies at modeling centers.

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P3DWL Operators

• Dan Carre’, Simpson Weather Associates– 26- 30 July ferry flight Pax river to Guam– 1 -17 August in Guam

• Michael Riemer, Naval Post Graduate School– 15 – 31 August

• Brian Tang, Massachusetts Institute of Technology– 28 – 15 September

• CDR Dan Eleuterio, NRL/ONR– 13 September – 3 October

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Acknowledgements

• Funding for this research is provided by The Office of Naval Research (Dr. Ronald Ferek) and the Integrated Program Office of the NPOESS (Dr. Stephen Mango).