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====== Doppler Lidar ======

//Mentor: [[http://www.geomet.uni-koeln.de/das-institut/mitarbeiter/schween/|J.H. Schween]]//

The instrument is a [[https://halo-photonics.com/lidar-systems/stream-line-series/|Streamline XR]] from [[https://halo-photonics.com | HALO Photonics ]] (Worcestershire, Great Britain) instrument nr.17 build in 2010.
===== 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.

===== Instrument =====

{{:instruments:p1040557.jpg?direct&255|}}\\
Instrument at [[http://www.fz-juelich.de/|Forschungszentrum Jülich]] on the roof of the IEK-8 ([[http://www2.fz-juelich.de/icg/icg-2/|Institut für Energie- und Klimaforschung: Troposphäre]]).


===== Data =====

  * If you are interested in receiving data please contact the instrument mentor [[http://www.geomet.uni-koeln.de/en/the-institute/rg-crewell/staff-crewell/schween/ | J.H. Schween]].

  * Recent plots can be found in the [[http://atmos.meteo.uni-koeln.de/~hatpro/dataBrowser/dataBrowser1.html?site=JOYCE&date=-1&UpperLeft=Windlidar_Overview|Quicklook archive]]

Current VAD plot:\\
[[http://atmos.meteo.uni-koeln.de/~jschween/wind_lidar/|{{http://atmos.meteo.uni-koeln.de/~jschween/wind_lidar/vad.png?400|click for more plots}}]]\\


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

===== History =====
^  Period  ^  Place  ^  Project  ^
| 12.9.2012 -   today   | [[http://www.fz-juelich.de/|Research Center Jülich]], Germany | [[http://www.tr32.de|TR32]] |
| 26.7.2012 - 31.8.2012 | [[https://maps.google.de/maps?q=50.91275522340144N+6.30132085102542E|Engelsdorf]], Germany | [[http://www.tr32.de|TR32]]-[[internal:experiments:patvap]] |
| 7.11.2011 - 26.7.2012 | [[http://www.fz-juelich.de/|Research Center Jülich]], Germany | [[http://www.tr32.de|TR32]] |



===== Specifications =====

^ Parameter  ^ Specification  ^ Remark  ^
| Wavelength / nm  | 1500nm  |  |
| Pulse energy / $\mu$J  | ~100  | see [[http://www.arm.gov/publications/tech_reports/handbooks/dl_handbook.pdf|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 /m$^2$)  | 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  | | [[http://halo-photonics.com/|Halo Photonics]]   |
| Year          | 2011 | |
| Instrument  | | [[http://halo-photonics.com/Halo%20Photonics%20Stream%20Line%20LiDAR%20system.htm|streamline ]] Instrument #17, XR version in 2010, 15kHz PRF, 10km max range   |