Mobile mini-DOAS measurement of the emission of NO₂ and HCHO from Mexico City

Abstract

Abstract. We here present the result of one mobile measurement using two ground based zenith viewing Differential Optical Absorption Spectroscopy (DOAS) instrument performed in a cross-section of the plume from the MCMA on the 10 March 2006 as part of the MILAGRO field campaign. The two instruments operated in the UV and the visible wavelength region respectively and have been used to derive the differential vertical columns of HCHO and NO2 above the measurement route. Using a mass-averaged wind speed and wind direction from the WRF model the instantaneous flux of HCHO and NO2 has been calculated from the two measurements and the results compared to the CAMx chemical model. The calculated flux through the measured cross-section was 1.9 (1.5–2.2) kg/s of HCHO and 4.4 (4.0–5.0) kg/s of NO2 using the UV instrument and 3.66 (3.63–3.73) kg/s of NO2 using the visible light instrument. The comparison with modeled values from CAMx shows a good agreement for the outflow of both NO2 and HCHO at this occasion.