Polly is a portable
two-channel mini Raman lidar. A frequency-doubled Nd:YAG laser emits
pulses at 532 nm with an energy of 120 mJ and a repetition rate of 15
Hz. A 20-cm Newton telescope collects the backscattered light. The
elastic signal and the vibration-rotation Raman signal of nitrogen at
607 nm are analyzed. In this way, extinction and backscatter
coefficients as well as the lidar ratio at 532 nm can be determined. Polly
is used for quasi-continuous,
semi-automated measurements in the lower troposphere.
Setup
| The optical parts of Polly are mounted on a
portable 100 x 70 cm² breadboard. The laser beam is expanded from
0.6 cm to 5 cm and directed by two steering mirrors into the field of
view of the Newtonian receiver telescope. The backscattered light is
separated into two different
channels, one for elastic backscattering at 532 nm and one for
inelastic scattering from nitrogen molecules at 607 nm. Photomultiplier
tubes are used for signal detection.
Backscatter-coeffcient measurements can be taken at any time of day,
and extinction coeffcients can be measured during nighttime. |
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Setup in an air-conditioned, weather-proof
housing
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Heart of Polly - the optical setup |
Measurements
Some test measurements were taken at IfT before Polly began
contributing to field experiments, e.g., the Pearl River Delta Experiment.
Latest Data from the Raman Lidar Polly
Projects
Publications
Engelmann, R. 2003. Entwicklung eines Mini-Ramanlidar und
Aufbau einer kombinierten Sende- und Empfangseinheit für ein
Doppler-Wind-Lidar. University of Leipzig, 57 pp. (Diploma
Thesis)
Rhone, P. 2004. Development of the data acquisition and
analysis systems for a portable Raman lidar and a Doppler wind lidar.
University of Leipzig, 72 pp. (Diploma Thesis)