Three-dimensional monitoring of air pollution using all-solid-state Lidar systems

Recent progress in Lidar/DIAL technology has allowed to obtain 3-dimensional mappings of the concentration of air pollutants at highest sensitivity (ppbrange) and over large distances (10 km)13. This access to atmospheric dynamics allows direct correlation between emission and immission. Presently, it is possible to monitor on-line distributions of nitrogen oxides, sulfur dioxide, and ozone. Recently, also the detection of toluene and benzene in the near UV has been demonstrated4. Routine or fully automatic operation has been severely restricted, however, by the complexity and maintenance of the usually employed Nd:YAG or Excimer-pumped dye lasers. The advent of new tunable all-solid-state laser systems, such as vibronic lasers (Ti:Sapphire, LICAF, LISAF,. ..) or laser-pumped OPOs, opens a new era in the domain of userfriendly and fully automatic DIAL operation. Here, we present the first Lidar/DIAL systems which are based on a high energy flashlamp-pumped Ti:Sapphire laser. It combines wide tunability of the laser medium with reliability and ease of operation, characteristic for flashlamppumped solid lasers. The wavelength range accessible by the laser and its extension by nonlinear optical devices makes it an ideal tool for both DIAL and meteorologic applications. This 'all solid state laser is the heart of a new generation of stationary and mobile Lidar systems. The first of these systems, presented here, has been designed to replace the urban station in Leipzig, which routinely provides mappings of pollutants over the city since 1992. The advantages of such routine and long term Lidar measurements are presented in this paper, in comparison with former results obtained during campaigns in several large european cities. A second urban unit is being implemented in Berlin, while a mobile and very compact all solid state DIAL system is in construction. It will start the test phase by the end of the year, and first measurement campaigns in february.