The design and construction of a differential absorption lidar (DIAL) system for measuring NO2 in the urban atmosphere are described. Two-wavelength laser beams in the blue region generated by a dye laser pumped by a Nd: YAG laser are used as the light source for the DIAL measurement. The wavelengths are switched alternately with the pulse repitition rate of 10 pps. The minimum detectabie NO2 concentration (signal-to-noiseratio=5) for the DIAL system is 10 ppb for a 10-minute measurement.
