Evaluation of NASA’s Remote-Sensing Capabilities in Coastal Environments

ABSTRACT
This work represents the second part of a two-part study set up by the National Aeronautics and
Space Administration (NASA) and Bureau of Ocean Energy Management (BOEM) in 2017. The
study summarizes a three-year investigation on the feasibility of using satellite remote sensing
to monitor emissions of oil and gas operations over the outer continental shelf (OCS) to
determine if they have negative impacts on coastal air quality (AQ). The target pollutant is
nitrogen dioxide (NO2), for which BOEM conducts regular emissions surveys. The major data
source for this report is a May 2019 oceanographic cruise (“SCOAPE” = Satellite Coastal and
Oceanic Atmospheric Pollution Experiment) conducted in the Gulf of Mexico (GoM) off
Louisiana with the Research Vessel Point Sur, loaded with a suite of trace-gas analyzers and a
direct-sun remote sensor Pandora spectrometer that measures column NO2. The SCOAPE
cruise, augmented by in situ NO2 and Pandora measurements at Cocodrie (Louisiana; 29.25° N,
90.66° W) showed that (1) under cloud-free conditions, satellites can detect elevated column
NO2 amounts near isolated large platforms and from clusters of smaller operations; (2) satellite
(the European Space Agency’s TROPOspheric Monitoring Instrument [TROPOMI]) total column
(TC) NO2 agrees well with TC NO2 from ground-based Pandora spectrometers (to 11–18%),
with the satellite biased low when pollution levels are higher; (3) in general, NO2 measured in
situ and in column amounts by Pandora or TROPOMI is greater over coastal Louisiana than
over the OCS; (4) the extent to which Pandora or satellite measurements correlate with surface
NO2 is highly variable.
It is recommended that BOEM and NASA continue to work together on collecting ground-truth
NO2 data and on interpreting remote sensing data for BOEM’s AQ requirements. Specific
recommendations:
1. BOEM and NASA should work together to analyze the 2019 SCOAPE data more
thoroughly, including conducting studies with tracers, ancillary satellite data, trajectories,
and appropriate chemical transport model output to more firmly establish the magnitude
of oil and natural gas influences on GoM AQ. Because remote-sensing measurements
(satellite- and ground-based) do not provide ambient NO2 concentrations, these studies
must be conducted to determine the column-surface NO2 relationship. NASA POC:
anne.m.thompson@nasa.gov
2. Coastal monitoring along the GoM with NASA and the Environmental Protection Agency
(EPA) using Pandora Spectrometer Instrument and other instruments would establish
better statistics and contribute to the ongoing improvements in OMI (Ozone Monitoring
Instrument) (mature algorithm) and the still evolving TROPOMI. Co-location with
BOEM’s coastal project, aiming to begin in late 2020 at a remote unpolluted location in
Louisiana, would greatly benefit BOEM. Daily overpass comparisons of OMI and
TROPOMI TC NO2 with a Pandora instrument would give BOEM more complete
statistics than the 5-week exploratory dataset of April–May 2019. Comparisons of the in
situ and column NO2 amounts, along with other pollutants being measured, would further
our understanding of the relationship of chemical transformation and interactions with
dynamical processes in the boundary layer. NASA POC:
anne.m.thompson@nasa.gov; barry.lefer@nasa.gov