Steffen Frey

Freie Universität Berlin, Physics Department, Arnimallee 14,14195 Berlin,Germany

The planetary boundary layer is characterized by turbulence and high concentrations of atmospheric pollution. Measurements of spatial resolved time series of planetary boundary layer properties are essential to study and understand a variety of optical, chemical and dynamical processes. For a lot of measurands lidar is the optimal solution, provided that the inversion problem, the calculation of the measurand out of the signal, can be solved satisfyingly. Furthermore the instrument setup should be simple enough, to guarantee reliable operation in harsh field environments outside the Laboratory. Changing aerosol properties are causing the main problem for trace gas measuremts with DIAL. Extinction result in an apparent concentration offset, which can be estimated very well in the case of pure Rayleigh scattering but less accurate for the aerosol part. Spatial gradients of aerosol properties along the laser beam may result in significant errors. Furthermore the temporal average over some laser shots, necessary to reach the appropriate signal to noise ratio for the required detection limit, is difficult in presence of small clouds and aerosol. At the same time, questioned information about the aerosol and the turbulence are lost, although they are included in the signal. I want to present a method and a recently developed compact instrument, which avoids the mentioned problems. Raman-DIAL is used for Ozone concentration retrieval. Under conditions of normal to high absolute humidity water vapor concentration is measured directly by its uv Raman shifted signal. Furthermore the aerosol backscatter coefficients at 3 wavelength from uv to ir, aerosol extinction coefficients in the ultraviolet and visible and the depolarization ratio of the green light are measured. The whole instrument is housed in an air-conditioned stainless steel outdoor enclosure. The receiving telescope and detector is mounted outside to allow vertical scanning.