INCA

funded by the European Community  through the Fifth Framework Programme

Interhemispheric differences in cirrus properties from anthropogenic emissions (INCA)

Department for Physics and Chemistry of the Atmosphere (SPCS)
 

Description of MARL

The Mobile Aerosol Raman Lidar (MARL) is a scientific measurement system, which is used for the detection and characterisation of small particles (Aerosol or clouds) in the atmosphere.

The ground-based system is integrated in a 20 ft standard container. The basic unit (Fig. 1) consist of a laser  (Tab.1)  and a telescope with a subsequent optical and electronic detection system  (Tab.2). The laser beam is directed vertically into the atmosphere. The detection unit measures the light scattered backwards on molecules and particles with a high time resolution (Tab.3).

During the INCA project in 2000 the system is used for the measurement of the actual hight and depth of cirrus clouds to assist the coordination of the Falcon aircraft flights. Further it allows the determination of the temporal and spatial evolution of the cloud and  its optical depth at the used wavelength. Characteristics of the cloud particles may be retrieved by analyzing the depolarisation behavior and the wavelength dependence of the backscattered light.

MARL took successfully part in the following field campaigns:

•  ALBATROSS, Fall 1996 on board RV POLARSTERN in the North- and  South-Atlantic ,
•  STRAIT'97, Spring 1997, Table Mountain Facility/Jet Propulsion Laboratory in South California/USA
•  NAOMI,Winter 1997/98 in Ny-Alesund, Svalbard, Arktic.
•  INCA, Spring 2000 Punta Arenas, Chile
•  LIMPIDO, Spring 2000 on board RV POLARSTERN in the South- and  North-Atlantic ,

For more information contact  Prof. Dr. Otto Schrems ,  Dr. Franz Immler

Fig. 1    The MARL container schematic setup
 
 

 
Tab. 1    Specifications of the transmitter

• Type  Nd:YAG, frequency doubled and tripled, Continuum
• Emitted wavelength 532 nm, 355 nm
• Energy 250 mJ at 532 nm and 355 nm
• Sending unit 10x beam expander, output diameter: 80 mm, divergence: 0.1 mrad

• Telescope type  Quasi- cassegrain A= 1140 mm, f = 3546 mm, overall f number: 1/3.1,
• Polychromator 9 channel polychromator, based on dichroic mirrors and narrowband filters
• Detectors Hamamatsu photomultipliers
• Digitizers Licel transient recorders, 12 bit, 20 MHz

•  Elastic aerosol backscatter ratio at 532 nm and 355 nm during day and night.
•  Aerosol depolarization at 532 nm and 355 nm during day and night.
•  Inelastic (vibrational Raman) backscattering  at 607 nm, 408 nm and 387 nm. (night time only)
•  Hight resolution: 7.5 m, time resolution (typical): 140 s.  Range: 3 to 30 km

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