Air quality impacts of COVID-19 lockdown measures detected from space using high spatial resolution observations of multiple trace gases from Sentinel-5P/TROPOMI

Abstract

Abstract. The aim of this paper is to highlight how TROPOspheric Monitoring Instrument (TROPOMI) trace gas data can best be used and interpreted to understand event-based impacts on air quality from regional to city scales around the globe. For this study, we present the observed changes in the atmospheric column amounts of five trace gases (NO2, SO2, CO, HCHO, and CHOCHO) detected by the Sentinel-5P TROPOMI instrument and driven by reductions in anthropogenic emissions due to COVID-19 lockdown measures in 2020. We report clear COVID-19-related decreases in TROPOMI NO2 column amounts on all continents. For megacities, reductions in column amounts of tropospheric NO2 range between 14 % and 63 %. For China and India, supported by NO2 observations, where the primary source of anthropogenic SO2 is coal-fired power generation, we were able to detect sector-specific emission changes using the SO2 data. For HCHO and CHOCHO, we consistently observe anthropogenic changes in 2-week-averaged column amounts over China and India during the early phases of the lockdown periods. That these variations over such a short timescale are detectable from space is due to the high resolution and improved sensitivity of the TROPOMI instrument. For CO, we observe a small reduction over China, which is in concert with the other trace gas reductions observed during lockdown; however, large interannual differences prevent firm conclusions from being drawn. The joint analysis of COVID-19-lockdown-driven reductions in satellite-observed trace gas column amounts using the latest operational and scientific retrieval techniques for five species concomitantly is unprecedented. However, the meteorologically and seasonally driven variability of the five trace gases does not allow for drawing fully quantitative conclusions on the reduction in anthropogenic emissions based on TROPOMI observations alone. We anticipate that in future the combined use of inverse modeling techniques with the high spatial resolution data from S5P/TROPOMI for all observed trace gases presented here will yield a significantly improved sector-specific, space-based analysis of the impact of COVID-19 lockdown measures as compared to other existing satellite observations. Such analyses will further enhance the scientific impact and societal relevance of the TROPOMI mission.

Estimation of NO2 emission strengths over Riyadh and Madrid from space from a combination of wind-assigned anomalies and a machine learning technique

“…The averaged NO 2 column decreased by ∼ 29 % as derived from TROPOMI observations and by ∼ 21 % as derived from OMI observations in Madrid during the lockdown period (Bauwens et al, 2020). These NO 2 reductions are strongly related to the lockdown policy and are also presented in the study by Levelt et al (2022), who reported that NO 2 column amounts decreased by 14 %-63 % in megacities globally. A sharp reduction of 54 % in the NO 2 tropospheric column amounts was observed in Madrid during the lockdown period, and a reduction of 36 % was noted during the transition period.…”

Air Pollution Inequality in the Denver Metroplex and its Relationship to Historical Redlining

“…The satellite retrievals used were measured by The TROPOspheric Monitoring Instrument (TROPOMI), the payload of the Copernicus Sentinel-5 Precursor (S5P) satellite. It has been well described and evaluated previously. , We used Level 2 NO 2 tropospheric column data, version 1.4.0 with a quality assurance value >0.5 to ensure no poor-quality data or highly clouded pixels were included while keeping high-quality snow-covered scenes. Physics-based oversampling was used to produce maps at a resolution of 0.01° × 0.01° at an annual average.…”

Underappreciated Emission Spikes From Power Plants During Heatwaves Observed From Space: Case Studies in India and China

“…OMI and TROPOMI NO 2 data are regridded to resolutions of 0.25°× 0.25°and 0.1°× 0.1°, respectively, based on an area-weighted tessellation. An extended area of 0.4°× 0.4°is adapted for SO 2 , considering its longer lifetime and higher noise than NO 2 , as recommended by Levelt et al (2022). We exclude power plants with limited anthropogenic emissions (mean SO 2 or NO 2 columns lower than 1 × 10 15 molec.…”