1. Huailin Chen, Bruce Gentry, Tulu Bacha, Belay Demoz, Demetrius Venable
Goddard Lidar Observatory for Winds (GLOW) Wind Profiling from the Howard University Beltsville Research Facility
Huailin Chen, Bruce Gentry, Tulu Bacha, Belay Demoz, Demetrius Venable
Destin, FL
February , 2010

2. NASA Wind Lidar Science (WLS) Experiment at Howard Beltsville Research Facility
GOALS
Develop understanding of direct detection (GLOW) wind speed and direction performance for various cloud and aerosol loading conditions (pollution, cirrus), using the 355nm backscatter ratios and water vapor data independently measured by the Raman lidar as well as synergistic measurements from the Beltsville instrument suite.
Develop a seasonal data base archive for wind measurements.
Intercomparison of coherent and direct detection Doppler lidars
Compare Doppler lidar wind data to other sensors (Profiler, Radiosonde, ACARS).
Funded by NASA SED, ROSES07-WLS (Dr. Ramesh Kakar)
A comparison of wind lidar technology is ongoing at the Howard University Beltsville Campus. The goal of the experiment was to compare two of NASA’s state-of-the-art wind lidar technology instruments. The VALIDAR is an aerosol-based lidar system from NASA/LaRC while the GLOW is a molecular-based lidar from NASA/GSFC. This experiment is the first time these two systems have been operated side by side. In addition, the commercial wind lidar from Leosphere, France (the WindCube), a 915 MHz profiler, ACARS winds and different types of radiosondes participated. 2

3. Goddard Lidar Observatory for Winds (GLOW) mobile Doppler lidar
Overview for GLOW
Goddard Lidar Observatory for Winds (GLOW) mobile Doppler lidar
Direct detection Doppler Lidar system
Measures clear air wind profiles using molecular backscatter
Serves as testbed for air and space based lidar technologies
Multiple field campaigns since 2000
Line of sight wind profiles are sequentially measured at 4 azimuth angles (N,S,E,W)+vertical. The multiple direction LOS profiles are combined to produce vertical profiles of horizontal wind speed and direction (right)
Measurement summary
Vertical resolution=250 m
t=3 min
Altitude range= 2 to 15 km
Elevation angle= 45 deg
Scan pattern = 4 directions: (N,S,E,W)+vertical
Dwell per LOS = 30 sec

4. GLOW at Beltsville Research Site

5. Upgrades for GLOW Laser ( 50Hz, 25mJ/pulse, Diode pumped )
Reference Signal Measurement
Electronics ( Preamps, discriminators, boxcar integrators)
Etalon Calibration

6. Laser Diode Pumped, 50Hz, 20mJ/pulse More Stable seed laser
Less energy consumption improves the temperature stability inside GLOW

7. Reference Measurement
Laser
Reference Signal Sampling Optics
Fiber
Collimator
Reference Signal Fiber
From Telescope
Lidar Signal Fiber M1
BS R=95%, T=5%
To Receiver
Lidar Signal+ Reference Signal IF

8. Etalon Calibration Scan

9. Wind Measurements in 2009 From Feb. 21 to Oct. 20, 50days, 310 hours
Variety weather conditions: different aerosol loadings, cirrus clouds at different altitude, front passage.
GLOW-Validar Intercomparison: Feb 21-Mar GLOW/Validar/AT/ALVICE HURL/Sonde/915 MHz profiler
Mar Campaign: Mar GLOW/AT/ALVICE HURL/Sonde/915 MHz profiler
Regular GLOW/Sonde comparisons

10. Measurement Errors

11. Results from March 2009 Campaign

12. Weather Conditions ref0903201250.edg 0.742 Cloud ref0903240002.edg
2.0986
Thin Cloud 8-10km
ref edg
1.2136
Clear
ref edg
1.7475
ref edg
3.35
ref edg
2.5064
Thin Cloud 8 and 11km
ref edg
0.8791
ref edg
3.7403
Increasing at 8,11km
ref edg
5.1409
ref edg
2.7287
ref edg
0.4775
mcs edg
ref edg
0.3003
mcs edg
ref edg
2.0066
mcs edg
ref edg
3.4847
mcs edg
ref edg
2.7164
mcs edg
Thin Clouds at 10
ref edg
5.0214

13. Results from March 2009 Campaign

14. Results from March 2009 Campaign

15. Comparison with Radio Sondes

16. Comparison with Radio Sondes

17. Comparison with Radio Sondes

18. Comparison with Radio Sondes

19. Comparison with Radio Sondes

20. Comparison with Radio Sondes

21. Comparison with IAD Sondes

22. Summary and Future Work
Wind measurement on regular basis
Sonde comparison validation
Continue wind data collection.
2 to 3 days a week
Coordinate with NWAVES
Use the GLOW data in WRF model
Participate field campaigns

23. Comparison with Radio Sondes

24. GLOW Lidar System Parameters
Wavelength nm
Telescope/Scanner Area m2
Laser Linewidth (FWHH) 80 MHz
Laser Energy/Pulse pps
Etalon FSR GHz
Etalon FWHH GHz
Edge Channel Separation GHz
Locking Channel Separation GHz
Interference filter BW (FWHH) 150 pm
PMT Quantum Efficiency 22%

25. Sampling strategy: Post processing: 2 1 5 34 5
Sampling strategy:
LOS scans at multiple azimuths
in repeating cycle (5-10 LOS /cycle)
Step stare scan pattern at fixed elevation angle (Typ. 45 deg) : 4 cardinal directions (N,S,E,W) + vertical
Signals are range gated in 30 m bins,
integrated and stored every 10 s. Three
dwells (30s total) per LOS. Total time to complete scan: ~3 min
Post processing:
data averaged in range (default 250 m)
data can be accumulated in time by LOS
(multiples of base 3 min)
corrections for atmos. T and P (RBS) 1 2 3 4 5

26. Backups

27. 1 2 3 4 5

28. Combined Molecular Sensitivity vs. T and v
T= 150K to 350K , v = 0 to 100 m/s