Trace atmospheric SO2 measurement by multiwavelength curve-fitting and wavelength-optimized dual differential absorption lidar.

We present a new differential absorption lidar (DIAL) method for atmospheric trace SO2 using multi-wavelength curve fitting. With this method we use five wavelengths around a SO2 absorption peak and obtain SO2 and O3 concentrations by fitting their absorption cross sections to measured DIAL and null results. A SO, concentration of 6 parts in 10(9) (ppb) was obtained for an altitude of 1050 m with 150-m range resolution. In addition, we optimized the wavelengths for dual-DIAL SO2 measurement and demonstrated a high sensitivity of <0.5 ppb with 300-m range resolution. Comparison of these two methods is also presented.