Measurement report: Spatiotemporal variability of peroxy acyl nitrates (PANs) over Mexico City from TES and CrIS satellite measurements

Abstract

Abstract. Peroxy acyl nitrates (PANs) are photochemical pollutants with implications for health and atmospheric oxidation capacity. PANs are formed via the oxidation of non-methane volatile organic compounds (NMVOCs) in the presence of nitrogen oxide radicals (NOx = NO + NO2). While urban environments are large sources of PANs, in situ observations in urban areas are limited. Here we use satellite measurements of PANs from the Tropospheric Emission Spectrometer (TES) and the Suomi National Polar-orbiting Partnership (S-NPP) Cross-track Infrared Sounder (CrIS) to evaluate the spatiotemporal variability of PANs over and around Mexico City. Monthly mean maxima in PANs over the Mexico City Metropolitan Area (MCMA) occur during spring months (March–May). This time of year coincides with a peak in local photochemistry and more frequent air stagnation. Local fire activity also typically peaks between February and May, which leads to strong interannual variability of PANs over the MCMA. We use S-NPP CrIS data to probe the spatial outflow pattern of PANs produced within urban Mexico City during the month with the largest mixing ratios of PANs (April). Peak outflow in April occurs to the northeast of the city and over the mountains south of the city. Outflow to the northwest appears infrequently. Using observations during 2018 versus 2019, we also show that PANs were not significantly reduced during a year, with a significant decrease in NOx over Mexico City. Our analysis demonstrates that the space-based observations provided by CrIS and TES can increase understanding of the spatiotemporal variability of PANs over and surrounding Mexico City.

Changes to Peroxyacyl Nitrates (PANs) Over Megacities in Response to COVID‐19 Tropospheric NO2 Reductions Observed by the Cross‐Track Infrared Sounder (CrIS)

“…Studies observing PAN from space thus far have focused on PAN enhancements associated with fires (Alvarado et al., 2011; Clarisse et al., 2011; Juncosa Calahorrano et al., 2021) and the global distribution of PAN and its role in the long range transport of O 3 (Fischer et al., 2018; Jiang et al., 2016; Payne et al., 2017; Zhu et al., 2015, 2017). Although TES had provided a set of special observations over select megacities (Cady‐Pereira et al., 2017; Shogrin et al., 2023), the spatial and temporal coverage of this data set is somewhat limited. Here, we utilize the more comprehensive spatial and temporal coverage of CrIS to explore the spatiotemporal distribution of PANs over and around megacities.…”

Transpacific Transport of Asian Peroxyacetyl Nitrate (PAN) Observed from Satellite: Implications for Ozone

“… 28 More recent observations from the cross-track infrared sounder (CrIS) have detected plumes from wildfires and metropolitan areas. 29 , 30 The IASI dataset is unique in its coverage and length, providing continuous global twice-daily mapping since 2007, 11 , 31 and has shown consistency with ground-based PAN column measurements at remote sites. 32 …”

“…Early observations from the tropospheric emission spectrometer (TES) captured plumes associated with boreal wildfires , but were too sparse to detect variability over the Pacific . More recent observations from the cross-track infrared sounder (CrIS) have detected plumes from wildfires and metropolitan areas. , The IASI dataset is unique in its coverage and length, providing continuous global twice-daily mapping since 2007, , and has shown consistency with ground-based PAN column measurements at remote sites …”

Measured and Modeled Trends of Seven Tropospheric Pollutants in the High Arctic From 1999 to 2022

“…In the past, efforts to measure tropospheric pollution in the Arctic were largely carried out on a short‐term campaign basis, and it is difficult to extrapolate information on intra‐ and inter‐annual variability from these temporally limited measurements (e.g., Alvarado et al., 2010; Law et al., 2014; Liang et al., 2011; Singh et al., 1992; Wofsy et al., 1992). Satellite observations of many reactive tropospheric pollutant species have been made from sensors such as the Measurements of Pollution in The Troposphere (MOPITT; e.g., Deeter et al., 2003), the Tropospheric Emission Spectrometer (TES; e.g., Cady‐Pereira et al., 2012, 2014; Payne et al., 2014), the Infrared Atmospheric Sounding Interferometer (IASI; e.g., Coheur et al., 2009; Franco et al., 2021; Pommier et al., 2016; Razavi et al., 2011), and the Cross‐track Infrared Sounder (CrIS; e.g., Payne et al., 2022; Shogrin et al., 2023). However, the observational conditions for thermal infrared nadir‐sounding instruments in the high Arctic are generally poor due to low thermal contrast and relatively low ambient concentrations of many pollutants, leading to higher uncertainties and sparser measurements than at lower latitudes.…”