LICHT lidar
Raman lidar system LICHT (LIdar for Cloud, Humidity and Temperature profiling) has been designed and built in 2013 to expand the observation capability of MPI-M and in particular to be replacement system for EARLI lidar deployed at that moment at BCO station. LICHT lidar having similar measurement characteristics to EARLI was already designed for high isolation from outdoor environment. Besides better protection against harsh environment the LICHT lidar has got capability of daytime water vapor measurements. Operation range has been extended from 15 km for EARLI to 29 km for LICHT (implemented on June 14, 2017). In addition, it has been equipped with automated window washing installation (built in and activated on July 7, 2017) that allowed significant improvement of data quality thanks to reduced transmission losses on output and input windows of lidar container. LICHT lidar system is deployed at BCO station since July 2016. For EUREC4A campaign it is planned to operate LICHT lidar from on-board of German research vessel Meteor.
Technical characteristics
| Pulse repetition rate | 10 Hz | ||
|---|---|---|---|
| Laser pulse energy | @ 355 nm | @ 532 nm | @ 1064 nm |
| 125 mJ | 125 mJ | 200 mJ | |
| Laser beam diameter | 80 mm | ||
| Laser beam divergence | 70 µrad | ||
| Operating range | @ 355 nm | @ 532 nm | @ 1064 nm |
| 0 - 15 (29) 1) km | 0 - 15 (29) 1) km | 0 - 15 km | |
| Receiving telescopes: | |||
| telescope ID | Focal length | Diameter | Field-of-view |
| “Far-range” | 2000 mm | 500 mm | 250 µrad |
| “Near-range” | 450 mm | 150 mm | 450 µrad |
| “Close-range” | 100 mm | 22 mm | 2000 µrad |
| “Depolarization” | 500 mm | 50 mm | 400 µrad |
1) measurement height limit for counted channels has been extended from 15 to 29 km on June 14, 2017
Parameters measured
| Product | Wavelength of emission stimulating lidar return |
|---|---|
| Attenuated backscatter | 1064, 532, 355 nm |
| Particle backscatter | 532, 355 nm |
| Particle extinction | 532, 355 nm |
| Volume linear depolarization ratio | 532 nm |
| Particle linear depolarization ratio | 532 nm |
| Cloud mask | 532, 355 nm |
| Water vapor mixing ratio | 355 nm |
| Air temperature | 355 nm |
| Relative humidity | 355 nm |
DATA ACCESS
Data collection recommended for scientific use is the calibrated quicklook dataset stored under:
/opt/pool/OBS/ACPC/RamanLidar-LICHT/3_QuickLook/nc/
For the period from June 2016 until July 12, 2017 the exact link for particular year, month, day timestamp of YYMMDD is given with:
/opt/pool/OBS/ACPC/RamanLidar-LICHT/3_QuickLook/nc/qlYYMM/jlYYMMDD0000.b[532|355]
Starting from July 12, 2017 the filename pattern has been slightly modified, respectively the data link has also changed reflecting the new filenames:
/opt/pool/OBS/ACPC/RamanLidar-LICHT/3_QuickLook/nc/qlYYMM/liYYMMDD.b[532|355]
Data are stored in netcdf format. Files with “532” in file extension combine together every lidar product related to atmospheric lidar response stimulated with the laser emission at 532 nm, respectively the “355” files bundle together the products related to atmospheric response to sounding laser emission at 355 nm.
To check data availability please have a look at the lidar quicklook web page:
http://bcoweb.mpimet.mpg.de/quicklooks/lidarql/RamanLidar-LICHT/
or download pdf plots directly from data server:
/opt/pool/OBS/ACPC/RamanLidar-LICHT/3_QuickLook/pdf/li20YY/liYYMM/jlYYMMDD.pdf before November 2017 /opt/pool/OBS/ACPC/RamanLidar-LICHT/3_QuickLook/pdf/li20YY/liYYMM/liYYMMDD.pdf since November 2017
Extending LICHT lidar data with temperature, relative humidity and particle extinction is in process.