Profiling of SO₂, NO₂, and O₃in the lower troposphere by multiwavelength differential absorption lidar

We performed SO₂, NO₂, and O₃ measurements in the lower troposphere using a multiwavelength differential absorption lidar (MDIAL) system. Measurement results are compared with results of airborne and ground-based in-situ measurements performed simultaneously with lidar measurement. Vertical concentration variation of SO₂ with 0-7 ppb for 1000-1700 m altitude was measured by dual-DIAL, and those of NO₂ and O₃ with 0-50 ppb for 700-2000 m altitude were measured by 2-wavelength DIAL quasi-simultaneously. Measurement results suggest that NO₂ was trapped below the inversion layer, which induced the reduction of O₃ concentration by the reaction with NO_X. Comparison of results obtained by DIAL and by in-situ methods showed that the MDIAL system had sufficient accuracy for verification of long-range transport models of sulfur compounds and for observation of chemical reactions of oxidants and nitrogen oxides. We also performed simultaneous profiling of NO₂ and O₃ in the lower troposphere using a stable, high power transmitter for NO₂ measurement. Concentration variations of NO₂ and O₃ for 900-1350 m altitude were measured for a continuous time interval of 24 hours without maintenance.