Evaluation of Uncertainties in the Anthropogenic SO Emissions in the USA from the OMI Point Source Catalog.

Satellite remote sensing is a promising method of monitoring emissions that may be missing in inventories, but the accuracy of these estimates is often not clear. We demonstrate here a comprehensive evaluation of errors in anthropogenic sulfur dioxide (SO) emission estimates from NASA's OMI point source catalog for the contiguous US by comparing emissions from the catalog with high-quality emission inventory data over different dimensions including size of individual sources, aggregate vs individual source errors, and potential bias in individual source estimates over time. For sources that are included in the catalog, we find that errors in aggregate (sum of error for all included sources) are relatively low.

Aircraft and satellite observations reveal historical gap between top-down and bottom-up CO emissions from Canadian oil sands.

Measurement-based estimates of greenhouse gas (GHG) emissions from complex industrial operations are challenging to obtain, but serve as an important, independent check on inventory-reported emissions. Such top-down estimates, while important for oil and gas (O&G) emissions globally, are particularly relevant for Canadian oil sands (OS) operations, which represent the largest O&G contributor to national GHG emissions. We present a multifaceted top-down approach for estimating CO emissions that combines aircraft-measured CO/NO emission ratios (ERs) with inventory and satellite-derived NO emissions from Ozone Monitoring Instrument (OMI) and TROPOspheric Ozone Monitoring Instrument (TROPOMI) and apply it to the Athabasca Oil Sands Region (AOSR) in Alberta, Canada.

Airborne Emission Rate Measurements Validate Remote Sensing Observations and Emission Inventories of Western U.S. Wildfires.

Carbonaceous emissions from wildfires are a dynamic mixture of gases and particles that have important impacts on air quality and climate. Emissions that feed atmospheric models are estimated using burned area and fire radiative power (FRP) methods that rely on satellite products. These approaches show wide variability and have large uncertainties, and their accuracy is challenging to evaluate due to limited aircraft and ground measurements.

Global fine-scale changes in ambient NO during COVID-19 lockdowns.

Nitrogen dioxide (NO) is an important contributor to air pollution and can adversely affect human health. A decrease in NO concentrations has been reported as a result of lockdown measures to reduce the spread of COVID-19. Questions remain, however, regarding the relationship of satellite-derived atmospheric column NO data with health-relevant ambient ground-level concentrations, and the representativeness of limited ground-based monitoring data for global assessment.

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

Unlabelled: We have investigated the impact of reduced emissions due to COVID-19 lockdown measures in spring 2020 on air quality in Canada's four largest cities: Toronto, Montreal, Vancouver, and Calgary. Observed daily concentrations of NO, PM, and O during a "pre-lockdown" period (15 February-14 March 2020) and a "lockdown" period (22 March-2 May 2020), when lockdown measures were in full force everywhere in Canada, were compared to the same periods in the previous decade (2010-2019). Higher-than-usual seasonal declines in mean daily NO were observed for the pre-lockdown to lockdown periods in 2020.

Disentangling the Impact of the COVID-19 Lockdowns on Urban NO From Natural Variability.

TROPOMI satellite data show substantial drops in nitrogen dioxide (NO) during COVID-19 physical distancing. To attribute NO changes to NO emissions changes over short timescales, one must account for meteorology. We find that meteorological patterns were especially favorable for low NO in much of the United States in spring 2020, complicating comparisons with spring 2019.

Enhanced Capabilities of TROPOMI NO: Estimating NO from North American Cities and Power Plants.

The TROPOspheric Monitoring Instrument (TROPOMI) is used to derive top-down NO emissions for two large power plants and three megacities in North America. We first re-process the vertical column NO with an improved air mass factor to correct for a known systematic low bias in the operational retrieval near urban centers. For the two power plants, top-down NO emissions agree to within 10% of the emissions reported by the power plants.

Exploiting OMI NO satellite observations to infer fossil-fuel CO emissions from U.S. megacities.

Fossil-fuel CO emissions and their trends in eight U.S. megacities during 2006-2017 are inferred by combining satellite-derived NO emissions with bottom-up city-specific NO-to-CO emission ratios.

High resolution mapping of nitrogen dioxide with TROPOMI: First results and validation over the Canadian oil sands.

Unlabelled: TROPOMI, on-board the Sentinel-5 Precursor satellite is a nadir-viewing spectrometer measuring reflected sunlight in the ultraviolet, visible, near-infrared, and shortwave infrared spectral range. From these spectra several important air quality and climate-related atmospheric constituents are retrieved at an unprecedented high spatial resolution, including nitrogen dioxide (NO). We present the first retrievals of TROPOMI NO over the Canadian Oil Sands, contrasting them with observations from the OMI satellite instrument, and demonstrate its ability to resolve individual plumes and highlight its potential for deriving emissions from individual mining facilities.

Assessing snow extent data sets over North America to inform and improve trace gas retrievals from solar backscatter.

Accurate representation of surface reflectivity is essential to tropospheric trace gas retrievals from solar backscatter observations. Surface snow cover presents a significant challenge due to its variability and thus snow-covered scenes are often omitted from retrieval data sets; however, the high reflectance of snow is potentially advantageous for trace gas retrievals. We first examine the implications of surface snow on retrievals from the upcoming TEMPO geostationary instrument for North America.

Author Correction: India Is Overtaking China as the World's Largest Emitter of Anthropogenic Sulfur Dioxide.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

India Is Overtaking China as the World's Largest Emitter of Anthropogenic Sulfur Dioxide.

Severe haze is a major public health concern in China and India. Both countries rely heavily on coal for energy, and sulfur dioxide (SO) emitted from coal-fired power plants and industry is a major pollutant contributing to their air quality problems. Timely, accurate information on SO sources is a required input to air quality models for pollution prediction and mitigation.

The effects of forest canopy shading and turbulence on boundary layer ozone.

The chemistry of the Earth's atmosphere close to the surface is known to be strongly influenced by vegetation. However, two critical aspects of the forest environment have been neglected in the description of the large-scale influence of forests on air pollution: the reduction of photolysis reaction rates and the modification of vertical transport due to the presence of foliage. Here we show that foliage shading and foliage-modified vertical diffusion have a profound influence on atmospheric chemistry, both at the Earth's surface and extending throughout the atmospheric boundary layer.

A decade of global volcanic SO emissions measured from space.

The global flux of sulfur dioxide (SO) emitted by passive volcanic degassing is a key parameter that constrains the fluxes of other volcanic gases (including carbon dioxide, CO) and toxic trace metals (e.g., mercury).

Tropospheric Emissions: Monitoring of Pollution (TEMPO).

TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (~2.

Marked long-term decline in ambient CO mixing ratio in SE England, 1997-2014: evidence of policy success in improving air quality.

Atmospheric CO at Egham in SE England has shown a marked and progressive decline since 1997, following adoption of strict controls on emissions. The Egham site is uniquely positioned to allow both assessment and comparison of 'clean Atlantic background' air and CO-enriched air downwind from the London conurbation. The decline is strongest (approximately 50 ppb per year) in the 1997-2003 period but continues post 2003.

A Decade of Change in NO2 and SO2 over the Canadian Oil Sands As Seen from Space.

A decade (2005-2014) of observations from the Ozone Monitoring Instrument (OMI) were used to examine trends in nitrogen dioxide (NO2) and sulfur dioxide (SO2) over a large region of western Canada and the northern United States, with a focus on the Canadian oil sands. In the oil sands, primarily over an area of intensive surface mining, NO2 tropospheric vertical column densities (VCDs) are seen to be increasing by as much as 10%/year, with the location of the largest trends in a newly developing NO2 "lobe" well removed from surface monitoring stations. SO2 VCDs in the oil sands have remained approximately constant.