Under daylight conditions the quality of lidar measurements is limited and conclusions drawn on the vertical profiling of optical and microphysical aerosol properties are subject to increased uncertainties. This is ought to the increased amount of solar background radiation that increases the noise level in the measured lidar signal profiles.

In the scope of the ACTRIS initiative WP-20 the research group Ground-based Remote Sensing deals with the integration of lidar and sunphotometer observations. Tasks are:

• The improvement of daytime capabilities of lidar instruments
• The generation of combined lidar/sunphotometer data sets at selected European stations influenced by different aerosol sources
• The development of combined retrieval algorithms for an improved characterization of thevertical aerosol distribution.

In 2012 extended tests of the LIRIC (Lidar/Radiometer Inversion Code)algorithm developed at the Institute of Physics in Minsk took place. Combined EARLINET/AERONETobservations of the Eyjafjallajökull ash cloud and of Saharan dust outbreaks at Leipzig were used toevaluate the potential of the method to derive concentration profiles of fine-mode and coarse-modeparticles. The results showed good agreement with those obtained with the POLIPHON (PolarizationLidar Photometer Networking) method developed at TROPOS.