A lidar for water vapour measurements in daytime at Lampedusa, Italy

P. Tini Brunozzi, F. Marenco


ENEA is planning to develop a lidar system for measurement of the vertical profi le of water vapour mixing ratio
in daytime at a remote site, the Station for Climate Observations located in Lampedusa, Italy. The Raman lidar
technique has been retained because of its experimental simplicity with respect to DIAL, and the UV spectral
range has been chosen because Raman cross-sections and detector effi ciencies are larger. For a wavelength larger
than ~ 300 nm the signal is limited in daytime by sky background, but extinction is acceptable, and the aims of
the system can be reached with a strong laser source. The 355 nm wavelength of a frequency-tripled Nd:YAG
laser has been retained as this laser source permits to reach a large pulse energy while keeping the system simple
to operate. Geometrical form factor calculations need to be performed to evaluate the near-range overlap between
the laser beam and the fi eld-of-view of the receiver. Among several options, a dual-receiver system has been
retained to account for the several orders of magnitude expected in the backscattered signal intensity: a smaller
receiver, with a primary mirror of 200 mm diameter for the 0.2-1 km range, and a larger 500 mm receiver for the
1-3 km range.


Raman lidar;water vapour

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DOI: https://doi.org/10.4401/ag-3419
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X