NH<sub>3</sub> spatiotemporal variability over Paris, Mexico City, and Toronto, and its link to PM<sub>2.5</sub> during pollution events
oleh: C. Viatte, R. Abeed, S. Yamanouchi, S. Yamanouchi, W. C. Porter, S. Safieddine, M. Van Damme, M. Van Damme, L. Clarisse, B. Herrera, B. Herrera, M. Grutter, P.-F. Coheur, K. Strong, C. Clerbaux, C. Clerbaux
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2022-10-01 |
Deskripsi
<p>Megacities can experience high levels of fine particulate matter (PM<span class="inline-formula"><sub>2.5</sub></span>) pollution linked to ammonia (NH<span class="inline-formula"><sub>3</sub></span>) mainly emitted from agricultural activities. Here, we investigate such pollution in the cities of Paris, Mexico, and Toronto, each of which have distinct emission sources, agricultural regulations, and topography. Ten years of measurements from the infrared atmospheric sounding interferometer (IASI) are used to assess the spatiotemporal NH<span class="inline-formula"><sub>3</sub></span> variability over and around the three cities.</p> <p>In Europe and North America, we determine that temperature is associated with the increase in NH<span class="inline-formula"><sub>3</sub></span> atmospheric concentrations with a coefficient of determination (<span class="inline-formula"><i>r</i><sup>2</sup></span>) of 0.8 over agricultural areas. The variety of the NH<span class="inline-formula"><sub>3</sub></span> sources (industry and agricultural) and the weaker temperature seasonal cycle in southern North America induce a lower correlation factor (<span class="inline-formula"><i>r</i><sup>2</sup>=0.5</span>). The three regions are subject to long-range transport of NH<span class="inline-formula"><sub>3</sub></span>, as shown using HYSPLIT cluster back trajectories. The highest NH<span class="inline-formula"><sub>3</sub></span> concentrations measured at the city scale are associated with air masses coming from the surrounding and north/northeast regions of Paris, the south/southwest areas of Toronto, and the southeast/southwest zones of Mexico City.</p> <p>Using NH<span class="inline-formula"><sub>3</sub></span> and PM<span class="inline-formula"><sub>2.5</sub></span> measurements derived from IASI and surface observations from 2008 to 2017, annually frequent pollution events are identified in the three cities. Wind roses reveal statistical patterns during these pollution events with dominant northeast/southwest directions in Paris and Mexico City, and the transboundary transport of pollutants from the United States in Toronto. To check how well chemistry transport models perform during pollution events, we evaluate simulations made using the GEOS-Chem model for March 2011. In these simulations we find that NH<span class="inline-formula"><sub>3</sub></span> concentrations are underestimated overall, though day-to-day variability is well represented. PM<span class="inline-formula"><sub>2.5</sub></span> is generally underestimated over Paris and Mexico City, but overestimated over Toronto.</p>