Assessing the Impact of Corona-Virus-19 on Nitrogen Dioxide Levels over Southern Ontario, Canada

Abstract

A lockdown was implemented in Canada mid-March 2020 to limit the spread of COVID-19. In the wake of this lockdown, declines in nitrogen dioxide (NO2) were observed from the TROPOspheric Monitoring Instrument (TROPOMI). A method is presented to quantify how much of this decrease is due to the lockdown itself as opposed to variability in meteorology and satellite sampling. The operational air quality forecast model, GEM-MACH (Global Environmental Multi-scale - Modelling Air quality and CHemistry), was used together with TROPOMI to determine expected NO2 columns that represents what TROPOMI would have observed for a non-COVID scenario. Applying this methodology to southern Ontario, decreases in NO2 emissions due to the lockdown were seen, with an average 40% (roughly 10 kt[NO2]/yr) in Toronto and Mississauga and even larger declines in the city center. Natural and satellite sampling variability accounted for as much as 20–30%, which demonstrates the importance of taking meteorology into account. A model run with reduced emissions (from 65 kt[NO2]/yr to 40 kt[NO2]/yr in the Greater Toronto Area) based on emission activity data during the lockdown period was found to be consistent with TROPOMI NO2 columns.

Isolating the impact of COVID-19 lockdown measures on urban air quality in Canada

“…5). Note that Griffin et al (2020) showed similar variations in NO 2 column values across the Toronto urban area based on an analysis of satellite NO 2 column measurements.…”

“…COVID-19-related emergency measures were introduced in North America later than in China or Europe. In Canada, such measures began in mid-March 2020, and reductions in air pollutant levels have been reported in different Canadian urban areas since March 2020 (Adams 2020;Griffin et al 2020;Rabson 2020;Xing 2020;MELCC 2020a). However, as the world's second-largest country but with a much lower population density than China or Europe, Canada poses a particular challenge for identifying AQ impacts from COVID-19 control measures.…”

Meteorological Drivers of Permian Basin Methane Anomalies Derived from TROPOMI

“…Because NO 2 has a short lifetime (1-12 h depending on the time of year) in the atmosphere before reacting to form secondary pollutants, the highest NO 2 enhancements will be relatively close to emission sources. As discussed in the Introduction, many recent studies have leveraged the high temporal and spatial resolution of TROPOMI to investigate the impacts of meteorological variables on the transport and spatial distribution of NO 2 [26][27][28][29][30][31][32][33][34][35][36][37].…”

“…The TROPOspheric Monitoring Instrument (TROPOMI) onboard the S-5P satellite contains four spectrometers that enable accurate, high resolution (temporally and spatially) retrievals for a number of atmospheric constituents (e.g., NO 2, CH 4 , carbon monoxide (CO), sulfur dioxide (SO 2 ), ozone (O 3 ), and aerosols [23]). The high spatial resolution of TROPOMI measurements has led to recent studies investigating the impacts of meteorological, social, or economic forcing (e.g., COVID-19 pandemic) on the spatial and temporal variability of NO 2 [26][27][28][29][30][31]. Recent studies across the world (e.g., Europe [32,33], Canada [34], USA [35], and China [36]) have linked changes in NO 2 to meteorological variations (e.g., solar angle and wind speed).…”

Situational Awareness of Large Infrastructures Using Remote Sensing: The Rome–Fiumicino Airport during the COVID-19 Lockdown

“…The former has been assessed in [17][18][19][20] by exploiting the TROPOspheric Monitoring Instrument (TROPOMI) [21] and the MODerate resolution Imaging Spectrometer (MODIS) [22]. Other research studies, instead, explicitly focused on Nitrogen Dioxide measurements [23,24]. Light pollution has also been considered in [25,26] as it is directly linked to air quality measurements.…”