Two-wavelength lidar still generates puzzles

Vertical profiles of aerosol extinction and "lidar ratios" of the lower troposphere in Thessalonica have been measured with two -wavelengths lidar. The extinction profile for the wavelength 355 nm seem to be insensitive for the time of the day. The profile for 532 nm has its maximum intensity at about 7 am, then decreases and increases during the afternoon and the evening. The vertical profiles of "lidar ratio" are structured for 355 nm but for 532 nm, are almost constant. It has been concluded that, at least, two different kinds of aerosols contribute to the observed profiles: one sensitive (532 nm) and a second one, insensitive for the changes in solar radiation (355 nm) during the day. Both, extinction and "lidar ratios" are characterized by high values for the wavelength 355 nm.