Evaluating current satellite capability to observe diurnal change in nitrogen oxides in preparation for geostationary satellite missions

Abstract

This study characterizes the degree to which current polar-orbiting satellites can evaluate the daytime change in NO 2 vertical column density (VCD) in urban, suburban, and rural areas. We examine these issues by considering the diurnal cycle of NO 2 over the United States, using the large NO 2 monitoring network supported by states, tribes, and the US Environmental Protection Agency (EPA). Through this analysis, we identify the potential opportunities and limitations of current space-based NO 2 data in capturing diurnal change. Ground-based monitoring data from the US EPA are compared with satellite retrievals of NO 2 from the KNMI Tropospheric Emissions Monitoring Internet Service (TEMIS) for two instruments: GOME-2 with a mid-morning overpass, and OMI with an early afternoon overpass. Satellite data show evidence of higher morning NO 2 in the vicinity of large urban areas. Both satellites and ground monitors show ∼1.5-2x greater NO 2 abundance between morning and afternoon in urban areas. Despite differences in horizontal resolution and overpass time, the two satellite retrievals show similar agreement with ground-based NO 2 measurements. When analyzed on a pixel-by-pixel basis, we find evidence for spatial structure in the diurnal change in NO 2 between city center and surrounding areas in Southern California. Wider analysis of urban-suburban structure in diurnal NO 2 change is hindered by resolution differences in the two satellite instruments, which have the potential to create data artefacts. This study highlights the value of future geostationary instruments to provide comparable satellite retrievals for NO 2 over the course of a day, and research needs related to the effective utilization of NO 2 satellite data for air quality applications.

TROPOMI NO2 in the United States: A Detailed Look at the Annual Averages, Weekly Cycles, Effects of Temperature, and Correlation With Surface NO2 Concentrations

“…Previous studies suggest that this underestimate is due to the AMF and ∼5km pixel size which cannot resolve street-level variations in concentrations (Goldberg, Lu, Streets, et al, 2019;Griffin et al, 2019;Judd, Al-Saadi, Szykman, et al, 2020;Judd, Al-Saadi, Janz, et al, 2019;Zhao et al, 2020); investigating the effects of the AMF bias on trends as well as investigating the effects of the pixels sizes will be the subject of future work. Also, there may be a clear-sky bias (Geddes, Murphy, et al, 2012) that NO 2 column measurements are lower and incrementally more spatially homogeneous in the afternoon than during the morning (Chong et al, 2018;Fishman et al, 2008;Herman et al, 2019;Knepp et al, 2015;Penn & Holloway, 2020;Tzortziou et al, 2015); it is likely that data from geostationary platforms such as TEMPO (Zoogman et al, 2017), GEMS (W. J. Choi, 2018), and Sentinel 4 (Timmermans et al, 2019), will be able to provide further insight on this time-of-day bias.…”

“…Since the satellite observation is acquired in the early afternoon, we suggest that the 24-h averaged NO X emissions difference between weekdays and weekends may be even greater than implied by the satellite data. The soon-to-be-launched TEMPO instrument, a geostationary satellite, will hopefully be able to better quantify the morning and evening differences of NO X emissions (Chance et al, 2019;Penn & Holloway, 2020;Zoogman et al, 2017).…”

Impacts of global NO<sub><i>x</i></sub> inversions on NO<sub>2</sub> and ozone simulations

“…Future geostationary satellite observations will provide opportunities to update NO x emissions at every hour. Separately constraining NO x emissions from the surface (e.g., anthropogenic sources) and the upper atmosphere (e.g., lightning sources, Pickering et al, 2016) as well as implementing these posterior NO x emissions at their corresponding vertical levels can potentially improve the vertical profile of ozone simulations.…”

Nitrogen dioxide decline and rebound observed by GOME-2 and TROPOMI during COVID-19 pandemic

“…For the urban and suburban Chinese regions, the NO 2 measurements from GOME-2 are generally larger than TROPOMI due to the diurnal cycle of NO 2 , which is a function of diurnal variability in emissions, photochemistry, and boundary layer height (Penn and Holloway 2020 ). Attributed in part to emissions from commuter traffic, which peak in the morning and evening (Bower et al 1991 ; Ketzel et al 2003 ; Harley et al 2005 ), the GOME-2 overpass could capture morning maximum NO 2 columns (Fishman et al 2008 ; Penn and Holloway 2020 ). In addition, the GOME-2 measurements are generally noisier as compared to TROPOMI results because of instrument degradation effects (Munro et al 2016 ).…”