OpenAQ Platform Informs Prize-Winning Publication

2 min readSep 28, 2022

Harmonized air quality measurements aid researchers

Congratulations to the Paul Crutzen Publication Awardee for 2021 in the journal Atmospheric Chemistry and Physics (ACP), Global impact of COVID-19 restrictions on the surface concentrations of nitrogen dioxide and ozone” written by Christoph A. Keller, Mathew J. Evans, K. Emma Knowland, Christa A. Hasenkopf, Sruti Modekurty, Robert A. Lucchesi, Tomohiro Oda, Bruno B. Franca, Felipe C. Mandarino, M. Valeria Díaz Suárez, Robert G. Ryan, Luke H. Fakes, and Steven Pawson!

This award for an outstanding publication in ACP that advances understanding of atmospheric chemistry and physics was inaugurated this year as part of the journal’s celebrations to mark their 20th anniversary. The paper was selected by an independent committee chaired by Annica Ekman of Stockholm University.

“This paper would not have been possible without OpenAQ, and both Christa Hasenkopf and Sruti Modekurty were co-authors on the paper,” says lead author Christoph A. Keller. “Our analysis builds on the recent development of unprecedented public access to air pollution model output and air quality observations in near-real time,” the paper reads. Harmonized air quality observations aggregated in the OpenAQ platform made it possible for the researchers to analyze otherwise disparate data from various sources.

Location of the observation sites included in the analysis, most of which were obtained from OpenAQ. Image from “Global impact of COVID-19 restrictions on the surface concentrations of nitrogen dioxide and ozone” by Keller, et al.

In this paper, Keller and colleagues investigated the nitrogen dioxide (NO2) and ozone (O3) throughout January 2018 to July 2020 using machine learning coupled with the NASA GEOS-CF model at 5,756 observation sites in 46 countries. They found that the NO2 trends were coincident with the COVID-19 restrictions, but the rate of decline was not the same all throughout the world — in European and US cities, the decline was gradual; however, in China the decline in NO2 was much faster. Moreover, in some other cities in the world, like Taipei and Rio de Janeiro, the reductions were small; however, others like Milan andWuhan, experienced a much larger decrease (up to 60%). On the other hand, ozone trends were more complicated: while ozone increased to up to about 50% in some locations, an overall impact on average daily ozone was not observed due to the fact that ozone increased at night (due to less NOx titration) and daytime ozone had decreased (due to less photochemical production).

This award was announced at the ACP 20th anniversary meeting in Mainz, and in this European Geosciences Union (EGU) press release. It will also be presented in person to the authors at EGU’s General Assembly in 2023.

Read the whole paper in ACP here.




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