Royal Netherlands Meteorological Institute; Ministry of Transport, Public Works and Water Management

CESAR Water Vapour, Aerosol and Cloud Lidar
Caeli in operation at CESAR (photo: MdG)

Caeli is the CESAR Water Vapour, Aerosol and Cloud Lidar and is a multiwavelength, high-performance Raman lidar, capable of providing round-the-clock measurements. It is deployed at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands (51* 58'N, 4* 56'E). The instrument was developed as a key instrument for CESAR to strengthen the sites capabilities as a profiling station for atmospheric research and climate studies. Next to the lidar, other profiling techniques also routinely operated provide synergy in observations.

Since the deployment at CESAR in May 2008, Caeli contributes to observation programmes and studies. The instrument is part of EARLINET, has provided data during the IMPACT and CINDI campaigns and provides correlative measurements for CALIPSO.

Caeli was set up as a high-performance, multi-wavelength Raman lidar. The instrument provides backscatter and exctinction profiles, depolarisation and water vapour profiles. Data is collected, suitable for input to retrieval of aerosol micro-physical parameters based on so-called 3B+2A schemes. Tropospheric coverage is provided, including part of the planetary boundary layer. Round-the-clock measurements are possible, although performance is degraded for water vapour and extinction due to high solar background.

The system is field deployed in a 20 ft. sea container making it transportable. The set-up requires external AC-power and internet to operate. The instrument itself, including the electronics is mounted in a single rugged aluminium frame that can be wheeled in and out of the container in its entirety. Windows are mounted on top of the frame above the receivers and in ports for the laser beams to weather-proof the system. Remote control of the system is foreseen. Various control and diagnostic features are added to the system for this purpose, including an active laser power optimisation system and an aircraft protection radar.

Temperature profiling capability using the pure rotational Raman technique is currently under development.

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Last update: 18 March 2016