Dual differential absorption lidar for the measurement of atmospheric SO2 of the order of parts in 109

Vertical concentration profiles of atmospheric SO2 of the order of parts in 10(9) (ppb) were measured by a multiwavelength differential absorption lidar system. The error that was due to O-3 and aerosols was successfully reduced by a three-wavelength dual differential absorption lidar (DIAL), and a SO2 concentration of 1.2 ppb for 2400-3000-m altitude was obtained with 300-m range resolution. The measurement error in dual DIAL was estimated to be <1.1 ppb when several factors were considered. The influence of O-3 on SO2 measurement error was experimentally evaluated from simultaneous measurements of atmospheric SO2 and O-3 by two conventional DIAL pairs, each using two wavelengths. (C) 2001 Optical Society of America OCIS codes: 000.2190, 010.7030, 140.2050, 280.1120, 280.1910, 280.3640.