Examination on photostationary state of NOx in the urban atmosphere in Japan

To investigate the photostationary state (PSS) of nitrogen oxides (NOx), fast and precise measurements of related compounds were simultaneously carried out in the urban atmosphere. A PSS parameter φ including the observed peroxy radical (ROx) was examined. Consequently, φ was not significantly different from unity in many cases. Observed NOx, O3, JNO2 and ROx could reasonably elucidate the PSS of NOx. Meanwhile, in some cases with large ROx/O3, φ was significantly less than unity. It was suggested that the reaction rate coefficients of ROx with NO could be critical for the PSS in the urban atmosphere. It was confirmed that the LIF instrument is promising to observationally approach the PSS of NOx.