Overview of the Raman lidar measurements in the frame of the HyMeX-SOP 1
Résumé
The University of BASILicata ground-based Raman Lidar system (BASIL) was deployed in
Candillargues (Southern France, Lat: 43°37' N, Long: 4° 4' E) in the frame of the
Hydrological Cycle in the Mediterranean Experiment - HyMeX. Within this experiment a
major field campaign (Special Observation Period 1-SOP1, September to November 2012)
took place over the North-western Mediterranean Sea and its surrounding coastal regions in
France, Italy and Spain, with a specific focus on the study of heavy precipitation and flashflood
events. During HyMeX-SOP1, BASIL operated between 5 September and 5 November
2012, collecting more than 600 hours of measurements, distributed over 51 measurement
days and 19 intensive observation periods (IOPs).
The major feature of BASIL is represented by its capability to perform high-resolution and
accurate measurements of atmospheric temperature and water vapour, both in daytime and
night-time, based on the application of the rotational and vibrational Raman lidar techniques
in the UV. This makes it an ideal tool for the characterization of the water vapour inflow in
Southern France, which is important piece of information to improve the comprehension and
forecasting capabilities of heavy precipitations in the North-western Mediterranean basin.
Besides temperature and water vapour, BASIL also provides measurements of the particle
(aerosol/cloud) backscattering coefficient at 355, 532 and 1064 nm, of the particle extinction
coefficient at 355 and 532 nm and of particle depolarization at 355 and 532 nm.
Measurements from this field deployment are illustrated and discussed in this presentation.
Specifically, we report on results concerning a water vapour inter-comparison effort,
involving the ground-based lidar BASIL, the airborne water vapour lidar LEANDRE 2 flying
on board the ATR42, as well as additional water vapour sensors on-site (radiosondes, GPS
tomography, aircraft in-situ sensors, microwave radiometers). The main objective of this
inter-comparison is providing accurate error estimates for these sensors. This effort benefits
from the few dedicated ATR42 flights in the frame of the EUFAR Project “WaLiTemp”. In the
present work our attention was focused on two specific case studies: 13 September and 2
October in the altitude region 0.5 – 5.5 km. Comparisons between BASIL and LEANDRE 2
indicate a mean relative bias between the two sensors of 6.5%, while comparisons between
BASIL and LEANDRE 2 vs. the radiosondes indicate a bias of 2.6 and -3.5 %, respectively.
Specific attention will also be dedicated to the WALI/BASIL inter-comparison effort which
took place in Candillargues on 30 October 2012. Specific results from this inter-comparison
effort will be illustrated and discussed at the Workshop.
Measurements from BASIL have also been considered to characterize Planetary Boundary
Layer moisture turbulence processes. In this respect a spectral analysis was carried out on the
high-resolution water vapour mixing ratio data for specific case studies. Results from these
further study will also be illustrated at the Workshop.