MétéoSuisse

Implementation of an operational water vapor and aerosol LIDAR system

The goal of this project is the realization of an operational water vapor and aerosol Lidar system for continuous profiling of the water vapor mixing ratio and the aerosol backscattering properties. The project is co-funded by MeteoSwiss (54%), the Swiss Federal Institute of Technology in Lausanne, EPFL, (39%) and the Swiss National Science Foundation (7%).
The agreement between MeteoSwiss and EPFL on the project was signed in Summer 2004. The Lidar system is build at EPFL by the LIDAR research team of Dr. V. Simeonov, part of the Air and Soil Laboratory of Prof. H. van den Bergh. It will be pre-operational for MeteoSwiss in 2007, and operational in 2008, after several calibration and intercomparison periods (comparison with sounding of Payerne, intercomparison campaign in Lindenberg scheduled for Spring 2007).

The MeteoSwiss-EPFL-LIDAR will supply data with high spatial (150 to 600 m vertical resolution) and temporal (typ. time steps of 15 to 60 min) resolution, thus helping to improve the database for direct meteorological applications by adding real time water vapor and aerosol backscatter profiling. It will provide MeteoSwiss and EPFL with a database of great importance for climate change modelling and trend analysis in aerosol and water vapor content in the troposphere.
Moreover, LIDAR information together with conventional data will be applied for comparison, validation and further development of the prognostic model aLMo.
The resulting "combined Swiss Alpine site" (Payerne, Arosa and Jungfraujoch), will enable MeteoSwiss to fulfil the requirements defined in the Global Water Vapor Project (GVaP) of WMO-GEWEX for a level-1 reference station.

The project will provide EPFL with:

A "spin-off" of its R&D in the field of lidar and atmospheric sciences.

As long term objectives, it will bring information and studies of interest for numerical research and modeling activities, possibilities for further work with MeteoSwiss, and also for participation in different national and international scientific programs.

Installation of the LIDAR

The system will be installed in a cabin, divided into two distinct rooms: a "white" room containing the system itself, with a hole in the roof allowing the Lidar beam to be sent and the backscattered light to be collected, and a computer room, from which the system will be operated (see Figure 1).

The LIDAR housing is divided into two distinct rooms.

Figure 1: Drawing of the Lidar housing, with separation into two distinct rooms (computer room for operation and acquisition on the right, and the Lidar ifself on the left).

Results

The lidar system is running in series of operation since early 2006. Current obtained results of vertical profile are shown in Figure 2.

Figure 2: Vertical profiles of water vapor mixing ratio [g/kg] from 14 to 24 UTC on 7 April 2006, and comparison with the Payerne sounding at 12 (left) and at 24 (right).

Key publications

Raman Frequency Shifting in CH4 :H2 :Ar mixture pumped by the 4th Harmonic of Nd :YAG (V. Simeonov, V. Mitev, H. van den Bergh, and B. Calpini) Appl. Opt., Vol 37, No 30, pp 7112-7115, 1998.

A Raman Differential Absorption Lidar for Ozone and Water Vapor Measurement in the Lower Troposphere (B. Lazzarotto, V. Simeonov, P. Quaglia G. Larchevêque, H. van den Bergh, and B. Calpini) Int. J. Env. Analytical Chem., 74, pp255-261, 1999

Experimental investigation of high-power single-pass Raman shifters in the ultraviolet with Nd :YAG and KrF lasers (L. Schoulepnikoff, V. Mitev, V. Simeonov, B. Calpini, and H. van den Bergh) Appl. Opt., Vol 36, No 21 pp 5026-5043, 1997.

Contacts

LIDAR-EPFL: Dr. Valentin Simeonov EPFL ENAC ISTE LPAS, CH C2 392, Station 6, CH-1015 Lausanne

MeteoSwiss: Prof. Bertrand Calpini, project leader, or Dr. Yves-Alain Roulet, project coordination, Aerological Station, P.O. Box 316, CH-1530 Payerne, Switzerland