Measurements of Nighttime Nitrate Radical Concentrations in the Atmosphere by Long-Path Differential Optical Absorption Spectroscopy

The long-path differential optical absorption spectroscopy (LP-DOAS) technique was developed to measure nighttime atmospheric nitrate radical (NO3) concentrations. An optimized retrieval method, resulting in a small residual structure and low detection limits, was developed to retrieve NO3. The time series of the NO3 concentration were collected from 17 to 24 March, 2006, where a nighttime average value of 15.8 ppt was observed. The interfering factors and errors are also discussed. These results indicate that the DOAS technique provides an essential tool for the quantification of NO3 concentration and in the study of its effects upon nighttime chemistry.