A differential absorption lidar system for simultaneous measurement of O₃ and NO₂ in the lower troposphere is developed. The system is based on a pair of Nd:YAG pumped dye lasers each capable of emitting two wavelengths on alternate pulses. Sum frequency generation is used to generate laser pulses of wavelengths 446.8 and 448.1 nm used for NO₂ measurement. O₃ concentrations of approximately 30 to 60 ppb and NO₂ concentrations of approximately 4 to 45 ppb are obtained for a vertical range of 1000 to 1500 m. Changes in O₃ and NO₂ concentration over a time interval of a few hours suggests an anticorrelation between these quantities. The measurement error, estimated from statistical error and instrumental error, is 2.5 ppb for O₃ concentration and 5.5 ppb for NO₂ concentration. In the case of NO₂ measurement, the error due to differential backscatter gradient is found to be a major source of error, but does not fully account for the measurement error.

Date Published: 1 January 2003
PDF: 7 pages
Opt. Eng. 42(1) doi: 10.1117/1.1525274
Published in: Optical Engineering Volume 42, Issue 1