We performed SO2, NO2, and 03 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 ofNO2 and 03 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 03 concentration by the reaction with NOR. 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 03 in the lower troposphere using a stable, high power transmitter for NO2 measurement. Concentration variations ofNO2 and 03 for 900-1350 m altitude were measured for a continuous time interval of 24 hours without maintenance.
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