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\title{Space-based~ Assessment of NOx Emissions from Global Oil and Gas Fields:
Bridging the Gap in~ Current Emission Inventories~~~~~~~~}



\author[1]{Piyushkumar Patel}%
\author[2,3]{Ritesh Gautam}%
\author[2,3]{Mark Omara}%
\affil[1]{Affiliation not available}%
\affil[2]{MethaneSAT LLC}%
\affil[3]{Environmental Defense Fund}%


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  \date{April 25, 2026}


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\begin{abstract}
Identifying air pollutant sources and quantifying related emissions
provides crucial information towards improving global air quality and
public health. Emission inventories commonly used for oil and gas (OG)
activities inadequately represent nitrogen oxide (NOx) emissions, with
notable discrepancies identified in the past. Satellite remote sensing
provides a unique vantage point to map and quantify several key
multi-pollutant species on a routine basis across the global scale.
Here, we quantify annual NOx emissions from 44 major OG basins
distributed globally, utilizing TROPOspheric Monitoring Instrument
(TROPOMI) nitrogen dioxide (NO2) observations with the divergence flux
method. In addition, we use the spaceborne Visible Infrared Imaging
Radiometer Suite (VIIRS) natural gas flaring detections to further
constrain satellite-derived NOx emissions. The divergence flux method,
which addresses 3D topography corrections and chemical loss of NOx while
accounting for wind-induced flux smearing, provides a robust approach
for estimating NOx emissions. Our findings reveal a substantial level of
NOx emissions from individual OG facilities and major production
clusters as well as flaring activity, which serve as valuable data for
assessing emission inventories. Subsequently, we conducted a comparative
analysis between our TROPOMI-derived NOx emissions and those obtained
from the existing EDGARv6.1 and CAMS-GLOB-ANT\_v5.3 global emission
inventories. This evaluation underscored a noteworthy disparity, with
existing inventories significantly reporting lower emissions from the OG
sector relative to TROPOMIderived data. Specifically, EDGAR exhibited a
substantially lower estimate of onshore emissions by 61\%, and CAMS
displayed an even pronounced lower estimate by 78\%, compared to
TROPOMI-derived data from this study. For offshore emissions, EDGAR
showed a similar pattern, albeit to a lesser extent, with a 26\%
underestimation, while CAMS showed a considerable underestimation of
92\%. These findings hold significance for enhancing global NO2 emission
inventories, particularly from OG fields, and therefore address gaps in
current bottom-up inventories. Additionally, our approach yields
detailed spatial emission maps, enhancing~granularity in depicting NOx
distribution.~We further explore the variations in the correlation
between NO\textsubscript{x} emissions with OG production volumes and
CH\textsubscript{4} concentrations across different OG basins in North
America. The observed co-locations and correlations provide important
insights into co-pollution emission characteristics of methane and NOx,
that are respectively a potent greenhouse gas and a reactive air quality
pollutant, linked to be originative from oil and gas activity. {}%
\end{abstract}%



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