Fig. 1. Schematic and photo of IBBCEAS experimental device. (a) Schematic; (b) photo

Fig. 2. Absorption cross sections of NO3 radical, NO2, and H2O

Fig. 3. Calibration of mirror reflectivity

Fig. 4. Allan variance versus average time

Fig. 5. Effective water vapor absorption cross section obtained by interpolation method

Fig. 6. Water vapor concentrations obtained by IBBCEAS instrument and commercial hygrometer

Fig. 7. Fitted absorption lines of NO3 and NO2 at different water vapor concentrations. (a) Measured (black) and fitted(red) absorption lines; (b) residual of fitting

Fig. 8. Fitted concentration retrieval results of NO3, NO2 and H2O in ambient air. (a) Measured (gray) and fitted (red) absorption spectra of NO3 radical (22.3×10-12), NO2 (6.9×10-9) and H2O (1.4%); (b) measured absorption spectrum of ambient air (gray) and fitted H2O absorption spectrum (red); (c) absorption spectrum after subtraction of H2O absorption (gray) and fitted NO3 absorption spectrum (red); (d) absorption spectrum after subtraction of H2O absorption and NO3 radical (gray) and fitted NO2 absor

Fig. 9. Time series of volume fractions of NO3 radical and NO2 in ambient air