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windlidar

Doppler wind lidar

HALO Doppler Lidar ©B. Pospichal
HALO Photonics Doppler wind lidar at JOYCE

Principle

The backscattered light from an emitted laserbeam is used to measure wind speed. Analysis of doppler shift gives wind speed along the beam. Combination of several beams allows an estimate of the three components of the wind vector. Amount of received backscattered light allows calculation of backscatter coefficient.

Measurement modes

  • Vertical staring mode (1.67 seconds temporal resolution)
  • Full azimuth and elevation scan capability

JOYCE-CF Standard Operation Procedures

The instrument performs several scanning patterns and uses the remaining time for vertical staring.

Scan patterns are currently:

  • Every 5 minutes doppler beam swinging (DBS) (12×14sec/hour=2min48sec/hour), i.e. one vertical and two tilted beams in eastern and western direction to derive instantaneous local wind profiles
  • Directly followed by a 3 beam VAD (VAD-3) (12×14sec/hour=2min48sec/hour), i.e. three tilted beams in at 0, 120 and 240 deg azimuth and 30deg zenith distance to derive instantaneous local wind profiles
  • Every 15 minutes a velocity azimuth display scan (VAD-36) (4×124sec/hour=8min16sec), i.e. a conical scan at 75oelevation to derive area averaged wind profiles
  • Every 60 minutes a range height indicator (RHI) (1×104sec/hour=1min44sec/hour), i.e. a vertical section from east to west with 5deg elevation steps (37beams)
  • The rest of the time is vertical staring, i.e. vertical staring is interrupted every 5 minutes and sums up to 47minutes/hour

Data availability

Most of the following data products are provided via the SAMD database. If you would like to have additional data or recent data that have not been uploaded to SAMD yet, please fill the data request sheet and send it to info@joyce.cloud

Dataset Temporal resolution File size Filename Retrieval / Remarks
Vertical stare data (Backscatter, Doppler velocity) 2 seconds 1 file per day (180 MB) sups_joy_dlidST00_l1_any_v00_YYYYMMDDHHMMSS.nc available on SAMD
3D wind profiles from custom scanning 5 minutes 1 file per day (3.3 MB) sups_joy_dlidCUST00_l2_wind_v00_YYYYMMDDHHMMSS.nc available on SAMD
3D wind profiles from Doppler beam swinging 5 minutes 1 file per day (3 MB) sups_joy_dlidDBS00_l2_wind_v00_YYYYMMDDHHMMSS.nc available on SAMD
Mixing layer height from vertical velocity 5 minutes 1 file per day (180 MB) sups_joy_dlidST00_l2_zmlaw_v00_YYYYMMDDHHMMSS.nc available on SAMD
3D wind profiles from VAD-36 15 minutes 1 file per day (1.6 MB) wind_vad-36_YYYYMMDD.nc

Current observations at quicklook archive

Measurement examples

Current wind profile:

Current VAD plot:

The figure shows a velocity azimuth display (VAD): vectors give direction and speed of horizontal wind at time and height. Vectors pointing upward indicate southerly winds, vectors pointing to the right indicate westerly winds. Color shading gives the backscatter coefficient.

Click here for more plots and explanations

Doppler lidar History

Period Place Project
12.9.2012 - today Research Center Jülich, Germany TR32
26.7.2012 - 31.8.2012 Engelsdorf, Germany TR32-patvap
7.11.2011 - 26.7.2012 Research Center Jülich, Germany TR32

Technical specifications

Parameter Specification Remark
Wavelength / nm 1500nm
Pulse energy / $\mu$J ~100 see ARM Doppler lidar handbook
Pulse width / ns (m) 150 (22.5) see ARM handbook
Repetition Rates / s 1/15000 i.e. 15000 laser pulses per second (=Pulse repetition frequency PRF)
1.67 avg.beam i.e. N_avg pulses averaged and processed ⇒ dead time=0.67s
300 Doppler Beam swing (DBS) with 3 beams ([azi,ele] = [0,90],[0,75],[90,75])
900 Velocity azimuth display (VAD) with 36 beams ([azi,ele] = [i*10,75])
3600 vertical slice (RHI) with 18 beams ([azi,ele] = [109,i*10])
N_avg 15000 number of pulses to be averaged in one 'beam'
resolution / m 30 range resolution (adjustable from 15m onward)
Field-of-View / deg 360 x 90 free alingment of the beam
maximum range / m 9000 adjustable, but restriced to sufficent backscatter (aerosol, cloud droplets or ice crystals)
velocity resolution / ms-1 0.0382 adjustable
velocity precsision / ms-1 < 0.20 for SNR > -17dB
max velocity / ms-1 19.2 = Nyquist Velocity (adjustable)
Aperture / mm (area /m2) 75 (4.417e-3) see ARM handbook
Size / cm³ 80 x 53 x 40
Average Power consumption / W 140/250 [600] (wo/w Heating/cooling) [The power supply shall provide 600W]
Weight / kg 110 with transport case
Manufacturer Halo Photonics
Year 2011
Instrument streamline Instrument #17, XR version in 2010, 15kHz PRF, 10km max range
windlidar.txt · Last modified: 2021/03/01 11:47 by bpospich