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Measurement report: Evolution and distribution of NH 3 over Mexico City from ground-based and satellite infrared spectroscopic measurements

par Herrera, Beatriz;Bezanilla, A.;Blumenstock, Thomas;Dammers, Enrico D. E.;Hase, Frank;Clarisse, Lieven ;Magaldi, Adolfo;Rivera, C.;Stremme, Wolfgang;Strong, Kimberly;Viatte, Camille;Van Damme, Martin ;Grutter, Michel
Référence Atmospheric chemistry and physics, 22, 21, page (14119-14132)
Publication Publié, 2022-11

Article révisé par les pairs

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Résumé :

Abstract. Ammonia (NH3) is the most abundant alkaline compound in theatmosphere, with consequences for the environment, human health, andradiative forcing. In urban environments, it is known to play a key role inthe formation of secondary aerosols through its reactions with nitric andsulfuric acids. However, there are only a few studies about NH3 inMexico City. In this work, atmospheric NH3 was measured over MexicoCity between 2012 and 2020 by means of ground-based solar absorptionspectroscopy using Fourier transform infrared (FTIR) spectrometers at twosites (urban and remote). Total columns of NH3 were retrieved from theFTIR spectra and compared with data obtained from the Infrared AtmosphericSounding Interferometer (IASI) satellite instrument. The diurnal variabilityof NH3 differs between the two FTIR stations and is strongly influencedby the urban sources. Most of the NH3 measured at the urban station isfrom local sources, while the NH3 observed at the remote site is mostlikely transported from the city and surrounding areas. The evolution of theboundary layer and the temperature play a significant role in the recordedseasonal and diurnal patterns of NH3. Although the vertical columns ofNH3 are much larger at the urban station, the observed annual cyclesare similar for both stations, with the largest values in the warm months,such as April and May. The IASI measurements underestimate the FTIR NH3total columns by an average of 32.2±27.5 % but exhibit similartemporal variability. The NH3 spatial distribution from IASI shows thelargest columns in the northeast part of the city. In general, NH3 total columns over Mexico City measured at the FTIR stations exhibited anaverage annual increase of 92±3.9×1013 molecules cm−2 yr−1 (urban, from 2012 to 2019) and 8.4±1.4×1013 molecules cm−2 yr−1 (remote, from 2012 to 2020),while IASI data within 20 km of the urban station exhibited an averageannual increase of 38±7.6×1013 molecules cm−2 yr−1 from 2008 to 2018.