This overview paper highlights the successes of the Ozone Monitoring Instrument (OMI) on board the Aura satellite spanning a period of nearly 14 years. Data from OMI has been used in a wide range of ...applications and research resulting in many new findings. Due to its unprecedented spatial resolution, in combination with daily global coverage, OMI plays a unique role in measuring trace gases important for the ozone layer, air quality, and climate change. With the operational very fast delivery (VFD; direct readout) and near real-time (NRT) availability of the data, OMI also plays an important role in the development of operational services in the atmospheric chemistry domain.
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.
The ultraviolet (UV) Absorbing Aerosol Index (AAI) is widely used as an indicator for the presence of absorbing aerosols in the atmosphere. Here we consider the TROPOMI AAI based on the 340 nm/380 nm ...wavelength pair. We investigate the effects of clouds on the AAI observed at small and large scales. The large-scale effects are studied using an aggregate of TROPOMI measurements over an area mostly devoid of absorbing aerosols (Pacific Ocean). The study reveals that several structural features can be distinguished in the AAI, such as the cloud bow, viewing zenith angle dependence, sunglint, and a previously unexplained increase in AAI values at extreme viewing and solar geometries. We explain these features in terms of the bidirectional reflectance distribution function (BRDF) of the scene in combination with the different ratios of diffuse and direct illumination of the surface at 340 and 380 nm. To reduce the dependency on the BRDF and homogenize the AAI distribution across the orbit, we present three different AAI retrieval models: the traditional Lambertian scene model (LSM), a Lambertian cloud model (LCM), and a scattering cloud model (SCM). We perform a model study to assess the propagation of errors in auxiliary databases used in the cloud models. The three models are then applied to the same low-aerosol region. Results show that using the LCM and SCM gives on average a higher AAI than the LSM. Additionally, a more homogeneous distribution is retrieved across the orbit. At the small scale, related to the high spatial resolution of TROPOMI, strong local increases and decreases in AAI are observed in the presence of clouds. The BRDF effect presented here is a first step – more research is needed to explain the small-scale cloud effects on the AAI.
Highly-resolved vertical profiles of ozone and reactive nitrogen in the lower troposphere were obtained using Millersville University's tethered balloon system and NASA's P-3B aircraft during the ...July 2011 Baltimore, MD/Washington DC and the September 2013 Houston, TX deployments of the NASA DISCOVER-AQ air quality field mission. The tethered balloon and surface measurement sites were located at Edgewood, MD and Smith Point, TX. The balloon profiles are used to connect aircraft data from the lowest portion of NASA's P-3B spirals (300 m AGL) to the surface thus creating complete profiles from the surface to 3–5 km AGL. The highest concentrations of surface ozone at these coastal sites resulted from mean flow transport of polluted air over an adjacent body of water followed by advection back over land several hours later, due to a bay or gulf breeze. Several meteorological processes including horizontal advection, vertical mixing, thermally direct circulation (i.e., bay, gulf, and, sea breezes) combined with chemical processes like photochemical production and deposition played a role in the local ozone maxima. Several small-scale, but highly polluted layers from the Chesapeake Bay advected landward over Edgewood, MD. The Houston Metro area was subject to large-scale recirculation of emissions from petrochemical sources by the Gulf of Mexico and Galveston Bay breezes.
•Thermally direct circulations can strongly alter air quality near bodies of water.•Large ozone concentration gradients could exist between water and its adjacent land.•Bay/gulf breeze circulations of varying magnitudes have profound impacts on ozone.
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