Airborne Doppler lidar surface returns: data products other than

tropospheric winds

G. D. Emmitt and C. O’HandleySimpson Weather Associates

Charlottesville, VA.

Hangzhou, China

October, 2002

TODWL: the program(Twin Otter Doppler Wind Lidar)

• SPAWAR and ONR 35/SBIR Program provided the lidar and supported its integration into the CIRPAS Twin Otter

• IPO has co-funded the lidar adaptation to the Twin Otter.

• IPO has solely funded the mission planning, flight hours, data collection and the post flight installation of the lidar in a trailer for inter-flight research.

TODWL : the aircraft

• Navy Twin Otter operated by CIRPAS out of Marina, CA

• Unpressurized (~ 10 ft normal operations)• Cruise speeds 100 - 140 kts• Equiped with:

– GPS/INS– Dropsonde– aerosol probes– temperature, water vapor, turbulence sensors

TODWL : the instrument

• 2µm coherent detection• 4-6 mJ (330 nsec pulse)• 80 Hz• water cooled• ~7-10% total system efficiency• 10 cm two axis scanner, side door mounted• GUI with realtime instrument control and data display• Weight: 250lb Power: 1.5 KW

TODWL 2-axis scanner

The Experiments

• Airborne missions over various water bodies (open ocean, surf zone, large rivers, lakes and wetlands) in the vicinity of Monterey, CA

• Laboratory studies using a water slide to simulate observations at differing incidence angles

Objectives

• Check out the operations of an airborne 2µm coherent, semi-hemispherical scanned DWL

• Investigate the utility of water surface returns at 2µm for space-based and airborne DWLs (ocean, lake, river, & wetlands)

• Compare DWL wind soundings with RAOBs, microwave sounders, met towers, ground-based DWLs and assorted surface observations

• Investigate the use of an airborne DWL to provide cal/val data for scatterometers and RadarSat

• Demonstrate the application of LAHDSSA for future space-based DWL missions.

• Collect aerosol data along with lidar data to assist in the interpretation of signals from the LAS

TODWL soundinglooking up (20seconds)

TODWL soundinglooking down (20 seconds)

Microwave soundingFt Ord (30 minutes)

0030 UTC March 2002

Aircraft flight level

Water surface returns as a function of incidence angle at 2µm with a coherent Doppler

lidar

Modeled reflectance from ocean surface for a wind speed of 7.5m/s (Tratt, 2002)

along wind direction

Cross wind direction

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ge f

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LAS returns

Water surface returns

Nadir angle

Relative spectral amplitude (range corrected)

using 400 shot integration

TODWL returns collected over Monterey Bay, 12 March 2002

Single shot data used to obtain 400 shot averageat ~3 degrees off nadir

Water surface

Single shot data used to obtain 400 shot averageat ~33 degrees off nadir

Water surface

400 shot integrated signal

saturations

TODWL signal as a function of nadir angle

Spectrum for range gate 20 associated with the data shown in previous slide. The data has notbeen fully corrected for the aircraft forward motion

WaterLAS

Observing ocean wave motion and the atmospheric

Layer Adjacent to the Surface (LAS)

Monterey Bay12 March 2002

Nadir view over water

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R H I N AD IR SC A NW ATER SU R FA C E VLO S (D ASH ED R ED )W ATER SU R FA C E S IG N AL AM PLITU D E (BLAC K)R U N N IN G A VG O VER 41 SH O TS (30 M )

TRO U G H

CR ESTCR EST

Investigation of Organized Large Eddies

within the Marine Atmospheric Boundary Layer

Summary

In addition to horizontal and vertical winds, an airborneDoppler lidar can be used to study water surface motionsand their correlations with aerosols. These correlationshave significance in the interpretation of data obtainedwith space based lidars and also the parameterizationof fluxes over water surfaces at wind speeds above thosethat produce whitecaps. The investigation of Organized Large Eddies will be among the objectives of futureTODWL flights

Acknowledgements

• This work was funded by the Office of Naval Research through the Center for Interdisciplinary Remotely-piloted Aircraft Studies and by the Integrated Program Office of NPOESS

TODWLTwin Otter Doppler Wind Lidar

Funded by USN and IPO

First Flight Series11-15 Feb. 2002

2 m lidar10 cm scanner(1st of its kind)

Navy Twin OtterOperated by

CIRPAS

Equipped for aerosolsampling

VADS to measureLOS component ofaircraft TAS

Signals 5 km aheadof aircraft for backscatter calibration using particleprobes

PIs: Emmitt and Bluth

TODWL obtaining a wind profile above the aircraft

CTI

Particle Probe Cluster

Cloud Streets over Monterey Bay, February, 2002

TODWL: participants

Simpson Weather Associates (SWA)

G. D. Emmitt (gde@swa.com) Science lead

C. O’Handley (coh@swa.com) Data processing and advanced algorithm development

S. Greco (sxg@swa.com) Ancillary data from sounders, buoys, numerical models and other data sources for comparison

Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS)

R. Bluth (rtbluth@nps.navy.mil) Platform lead

Nava Roy (nava_roy@hotmail.com) Software support

Haf Jonsson (hjonsson@nps.navy.mil) Aerosol probe data responsibility

Mike Duncan (mhduncan@cirpas.org) Project oversight

Roy Woods (rkwoods@cirpas.org) Pilot and aircraft systems engineer

Mike Hubbell (mhubbell@aol.com) Chief pilot

Coherent Technologies Incorporated (CTI)

Steve Shertz (steves@ctilidar.com) TODWL would not have happened without his technical support

Phil Gatt (philg@ctilidar.com) Project responsibility within CTI. Also provided experience based input to the operations of the TODWL lidar

Rod Munson (RodneyM@ctilidar.com) Software support.

University of Alabama at Huntsville (UAH)

David Bowdle (David.Bowdle@msfc.nasa.gov) Aerosol/Lidar backscatter

University of Washington (UW)

Ralph Foster (ralph@apl.washington.edu) Arranged for RADARSAT data collection over the Monterey Bay during TODWL flights.

Robert Brown (rabrown@atmos.washington.edu) Involved in the interpretation of QuikScat and RADARSAT data taken during TODWL under-flights

United States Geological Survey (USGS)

John Costa (jecosta@usgs.gov) Arranged for surface flow velocity observations on the San Joaquin River during TODWL overflights.

NOAA Environmental Technology Laboratory (ETL)

M. Hardesty (michael.hardesty@noaa.gov) Helped arrange for lidar operations during TODWL over flights

A. Brewer (abrewer@etl.noaa.gov) Operated NOAA’s lidars during the overflights

TODWL Data Inventory and Experiment Summary Series 1 (February, 2002) Date Experiments Time(PST) Other Data Comments 2/09/02 Ground based

checkout 1102 – 1138 None Checking on pointing

directions relative to aircraft.

2/11/02 Engineering checkout flight

1700 – 1751 None Not well documented for analysis

02/13/02 Under flights of RADARSAT and QuikScat; Ocean surface returns; Aircraft attitude checks; Backscatter runs using different view angles

0630 - 0915 RADARSAT QuikScat FT.Ord Microwave Buoy data Eta Model fields GOES images

Saw cloud streets over bay; Ocean waves with small areas of whitecaps; several transects of shoreline near Ft. Ord.

02/14/02 Lake, river and canal over flights; flight above marine strat.

1445 - 1815 USGS Observations of surface velocity on San Joaquin River

Focus of flight was on the river surface observations. Flight legs at 6500 ft provided opportunities to take down VADS, nadir (up and down) stares, and cloud reflectivity observations

02/15/02 Dropsonde comparisons and VADS over land and water

1325 - 1500 Ft. Ord microwave; Buoys Dropsondes(2)

The two dropsondes were deployed from 6500 ft and were dropped through a cloud layer.

Series 2 (March, 2002) Date Experiments Time (PST) Other Data Comments 03/12/02 Long transects of Bay

to get variety of water reflectance data and wind profiles; Comaprison with Ft Ord microwave; Lidar and probe data comparisons.

1430 – 1638 Ft Ord Sounder CODAR?? Accelerometer Probes

Best set of data for water reflectance from different angles. Also good data for up and down VADS. Also good data fro probe comparisons

03/13/02 Trip from Monterey to Boulder via Las Vegas.

1010 - 1735 Probes Had to limit operations below 12000ft to protect hard drives. Most of flight was at 17000ft. Very strong winds near Las Vegas..dust storm

03/14/02 Grounded due to icing conditions

1227 –1238 BAO Took some raster scans while sitting on ramp. Interesting wind structures seen.

03/15/02 Overflights of ground based lidars, BAO tower and Platteville microwave sounder

0928 – 1116 (LST)

CTI lidars NOAA lidars BAO tower Platteville Microwave sounder Probes

Overflights at 10500 scanning down; overflights at 6500 scanning up. Lots of snow returns during down VADS.

Returns over Monterey Bay during 1 second

LAS returns

Water returns