Scanning 6-wavelength 11-channel aerosol lidar

A transportable multiple-wavelength lidar is presented, which is used for t he profiling of optical and physical aerosol properties. Two Nd:YAG and two dye lasers in combination with frequency-doubling crystals emit simultaneo usly at 355, 400, 532, 710, 800, and 1064 nm. A beam-combination unit align s all six laser beams onto one optical axis. Hence the same air volume is o bserved by all six beams. The combined beam can be directed into the atmosp here from -90 degrees to + 90 degrees zenith angle by means of a turnable m irror unit. From the simultaneous detection of the elastic-backscatter sign als and of the Raman signals backscattered by nitrogen molecules at 387 and 607 nm and by water vapor molecules at 660 nm, vertical profiles of the si x backscatter coefficients between 355 and 1064 nm, of the extinction coeff icients, and of the extinction-to-backscatter ratio at 355 and 532 nm, as w ell as of the water vapor mixing ratio, are determined. The optical thickne ss between the lidar and a given height can be retrieved for all six transm itted wavelengths from measurements under two different zenith angles. In c ontrast to sun-radiometer observations, this option allows the resolution o f spectral extinction information of each of the aerosol layers present in the vertical. The profile of the depolarization ratio is determined at 710 nm and used to investigate particle shape. A few measurement cases are pres ented to demonstrate the capabilities of the new lidar.