Contact: G.Liberti,

ISMAR - CNR,

Via Fosso del Cavaliere 100,

Rome, I-00133, Italy.

gianluigi.liberti@cnr.it

 

 

 

 

 

The Rayleigh-Mie-Raman (RMR) lidar of CNR Rome - Tor Vergata

 

 

 

 

 

 

                                   

                                 Instrument description

 

                                 Geographical site

 

                                 Raman Lidar data

 

                                 Contact

 

                                 References
 

 

 

Instrument description

 

A  multichannel RMR lidar system was designed and set up, and now is operative, in the ISMAR/CNR section of Rome-Tor Vergata. The system is assembled in two overlaying containers and can be utilized for routinely in situ observations or transported for measurement campaigns in remote sites. The Raman lidar is currently utilized to study the water vapor (WV) vertical distribution and its seasonal climatology. For this kind of nighttime measurements, the sounding ranges between the very first layers of the PBL up to close the tropopause.  The acquisition resolution is 75 m in altitude and 1 min in time. For upper tropospheric information, software integration is recommended to improve the result quality, with a degraded resolution to 500 m in altitude and 10-20 min in time. In daytime measurement, the sounding range is reduced down to 3-5 km. The lidar can simultaneously supplies temperature profiles in the aerosol free atmosphere (upper stratosphere and mesosphere) through the Rayleigh lidar technique and aerosol profiles from the boundary layer up to the uppermost aerosols layers in stratosphere. Currently a regular protocol of data acquisition is applied producing a baseline set of observations sessions: at least one 4-5 hours session of measurement for each calendar week. Extra sessions are performed in case of occurrence of interesting cases. Data are stored together with the high resolution radiosounding from the nearby Italian Meteorological Service station of Pratica di Mare (WMO #16460) that are successively used to calibrate the lidar profile. Processing of the data is performed according with special needs and available resources.

The system uses two beams at 532 nm and 355 nm, second and third harmonics of a Nd:YAG laser. The green (532nm) radiation is used to retrieve aerosol and temperature by using the elastic backscattering signal; the UV (355nm) is used to produce and detect Raman-shifted backscattering signals, originated both by nitrogen (387 nm) and by water vapor (407 nm) .  The lidar receiver is a multi-channel system, each channel having the proper sensitivity for sounding a different altitude sub-range. (Figure 1)

 

 

 

Transmitter

Wavelenghts

532 nm and 355 nm

Pulse energy

200 mJ and 400 mJ

Repetition rate

10 Hz

Receiver

Telescope 1

15 cm diameter

Telescope 2:

30cm diameter

Telescope 3:

9 mirrors of 50 cm diameter array

 

Figure 1. Raman lidar schematic plan

 

 

Figures 2 and 3 show examples of processed time series of water vapor profiles and applications.

 

 

Figure 2. Log-contour of a 5-hour measurement session (left) and WV estimate profile (red line) compared with Pratica di Mare radiosonde profile (black line) (20 min integration).

 

 

Figure 3: Example (inner panel) of distribution of mixing ratio in the pseudo volume defined by the white boundaries

 

Geographical site

 

At present the Raman lidar system is installed in the Tor Vergata atmospheric observation field of the Institute. The observation field is at about 15 km SE from Rome (Figure 4) in a rural environment where also different instruments are located (3 axes sodar, radiometers, AERONET sunphotometer, meteorological station, radar wind profiler….) (Figure 5).

Hosting of instrumentation from external laboratories in the Tor Vergata observation field is possible through joint agreements and according with available resources needed for the correct instrument operation and maintenance.

 

Figure 4. - Position of the Tor Vergata Atmospheric observation field (red and yellow dot). Also reported the position of the Italian Meteorological Service station of Pratica di Mare (WMO # 16460) (southernmost yellow dot).

 

  Figure 5. - Panoramic view of the Tor Vergata Atmospheric observation field. The Raman lidar is assembled in two white overlaying containers on the right.

 

 

Raman Lidar data

 For every single year of measures, in this section, it's possible to visualize the results of  the processed time series of water vapor profiles in the form of quicklook images (jpg)

 

References

 

 

Congeduti, F., F. Marenco, P. Baldetti, and E. Vincenti, The multeple mirror lidar "9-eyes", J. Opt. A: Pure Appl. Opt., 1, 185-191, 1999.

 

Congeduti F., C.M. Medaglia, P. D'Aulerio, F. Fierli, S. Casadio, P. Baldetti, F. Belardinelli, A powerful trasportable Rayleigh-Mie-Raman Lidar System, in Lidar Remote Sensing in Atmospheric and Earth Sciences, Proceeding of XXI International Laser Radar Conference, L. Bissonette ed., Quebec-City, Canada,  July,8-12, pp. 23-26, 2002

 

D'Aulerio P., F. Fierli, F. Congeduti, C.M. Medaglia, M. Baldi, S. Casadio, Lidar water vapour measurements during the MAP campaign, in Lidar Remote Sensing in Atmospheric and Earth Sciences, Proceeding of XXI International Laser Radar Conference, L. Bissonette ed., Quebec-City, Canada, July 8-12, pp. 547-549, 2002

 

D’Aulerio P., F. Fierli, F. Congeduti, G. Redaelli, Analysis of the water vapor Lidar measurements during the MAP campaign: evidence of sub-structures of stratospheric intrusions, Atmos. Chem. Phys., 5, 1301–1310, 2005

 

Liberti G.L, F. Cheruy, F. Congeduti, D. Dionisi, C. Transerici, Caratterizzazione della variabilitą spazio-temporale del vapor d’acqua come diagnostico per un modello di clima. Clima e Cambiamenti climatici: le attivitą di ricerca del CNR, 35-38, 2007

 

Dionisi D., F. Congeduti, G.L. Liberti, F. Cardillo, Automatic calibration procedure for Raman lidar water vapor profiles through Noncollocated operational radiosoundings, Proceeding of 24st International Laser Radar Conference, Boulder, 1037-1040, 2008

 

Dionisi D., F. Congeduti, G.L. Liberti, F. Cardillo, Calibration of a Multichannel Water vapor Raman Lidar through Noncollocated Operational Soundings: Optimization and Characterization of Accuracy and Variability, J. Atmos. Ocean. Tech.,, 27, 108-121, 2002

 

Dionisi D., G.L. Liberti, F. Cheruy, F. Congeduti, Multi-sensor investigation of atmospheric Water Vapour Probability Distribution Function in the free troposphere for a Mediterranean coastal site, Proceeding of 25st International Laser Radar Conference, St. Petersburg, 2010