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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ru(NO2)6 by Materials Project

(RuN4O11)2N2(NO)2 crystallizes in the monoclinic P2_1 space group. The structure is zero-dimensional and consists of two ammonia molecules, two nitroxyl molecules, and two RuN4O11 clusters. In each RuN4O11 cluster, Ru4+ is bonded in a distorted see-saw-like geometry to one N+3.33+ and three O2- atoms. The Ru–N bond length is 1.70 Å. There are a spread of Ru–O bond distances ranging from 1.74–2.09 Å. There are four inequivalent N+3.33+ sites. In the first N+3.33+ site, N+3.33+ is bonded in a single-bond geometry to one Ru4+ atom. In the second N+3.33+ site, N+3.33+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.25 Å) and two longer (1.26 Å) N–O bond length. In the third N+3.33+ site, N+3.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.23–1.35 Å. In the fourth N+3.33+ site, N+3.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.23–1.36 Å. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Ru4+ and one O2- atom. The O–O bond length is 2.67 Å. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two O2- atoms. The O–O bond length is 2.85 Å. In the third O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ and one O2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Ru4+ and one N+3.33+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to one Ru4+ and one N+3.33+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom. In the eleventh O2- site, O2- is bonded in a single-bond geometry to one N+3.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeS6(NO2)9 by Materials Project

(Fe(SO3)6)2(N2)9 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of nine ammonia molecules and one Fe(SO3)6 cluster. In the Fe(SO3)6 cluster, Fe3+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Fe–O bond distances ranging from 1.96–2.32 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.43 Å) and one longer (1.45 Å) S–O bond length. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of S–O bond distances ranging from 1.46–1.56 Å. In the third S2- site, S2- is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.43 Å) and one longer (1.44 Å) S–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S2- atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S2- atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one S2- atom.

36 MATERIALS SCIENCE↗
NASA NTRS2001

The NO(x)-HNO3 System in the Lower Stratosphere: Insights from In Situ Measurements and Implications of the J(HNO3)-[OH] Relationship

During the 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) mission, simultaneous in situ observations of NOx and HOx radicals, their precursors, and the radiation field were obtained in the lower stratosphere. We use these observations to evaluate the primary mechanisms that control NOx-HNO3 exchange and to understand their control over the partitioning between NO2 and HNO3 in regions of continuous sunlight. We calculate NOx production (PNOx) and loss (LNOx) in a manner directly constrained by the in situ measurements and current rate constant recommendations, using approaches for representing albedo, overhead O3 and [OH] that reduce model uncertainty. We find a consistent discrepancy of 18% between modeled rates of NOx production and loss (LNOx = 1.18P(sub NOx)), which is within the measurement uncertainty of +/- 27%. The partitioning between NOx production processes is [HNO3 + OH (41 +/- 2)%; HNO3 + hv (59 +/- 2)%] and between NOx loss processes is [NO2 + OH, 90% to >97%; BrONO2 + H2O, 10% to <3%]. The steady-state description of NOx-HNO3 exchange reveals the significant influence of the tight correlation between the photolysis rate of HNO3 and [OH] established by in situ measurements throughout the lower stratosphere. Parametrizing this relationship, we find: (1) the steady-state value of [NO2](sub 24h-avg)/[HNO3] in the continuously sunlit, lower stratosphere is a function only of temperature and number density; and (2) the partitioning of NOx production between HNO3 + OH and HNO3 + hv is nearly constant throughout most of the lower stratosphere. We describe a methodology (functions of latitude, day, temperature, and pressure) for accurately predicting the steady-state value of [NO2](sub 24h-avg)/[HNO3] and the partitioning of NOx production within these regions. The results establish a metric to compare observations of [NO2](sub 24h-avg)/[HNO3] within the continuously sunlit region and provide a simple diagnostic for evaluating the accuracy of models that attempt to describe the coupled NOx-HOx photochemistry in the lower stratosphere.

Perkins, K. K.↗
NASA NTRS1977

Kinetics of the reactions of ClO with O and with NO

The rate constants k1, k2, and k3 for the reactions Cl + O3 yields ClO + O2 (1), ClO + O yields Cl + O2 (2), and ClO + NO yields Cl + NO2 (3), respectively, were measured by the discharge-flow technique, in which chlorine atoms are added to a flow of O3 and either O or NO in a helium carrier gas. The conditions of the experiment were such that the steady-state concentration ratios of Cl to ClO are simply interpretable in terms of the rate constant ratios k2/k3 or k3/k1. These rate constant ratios were measured over the range 220 to 298 K and combined with the directly determined k1 value to yield k2 and k3. The results are: k1 = 2.12 x 10 to the -11th exp(-157/T); k2 = 3.38 x 10 to -11th exp(75 plus or minus 40/T); and k3 = 1.13 x 10 to the -11th exp(200 plus or minus 30/T) cu cm/sec.

Zahniser, M. S.↗
NASA NTRS1990

Operational overview of NASA GTE/CITE 2 airborne instrument intercomparisons - Nitrogen dioxide, nitric acid, and peroxyacetyl nitrate

This paper provides the rationale, objectives, approach, and a brief description of the instrumentation included in the second airborne Chemical Instrumentation Test and Evaluation (CITE 2) mission conducted on NASA's Electra aircraft. CITE 2 intercompared data from instruments measuring NO2, HNO3, and PAN in the troposphere. This study, conducted in August 1986, encountered marine and continental air with free tropospheric mixing ratios of NO2, HNO3, and PAN typically less than 120, 150, and 200 parts per trillion by volume, respectively.

Hoell, James M., Jr.↗
NASA NTRS1994

The radical amplifier

The radical amplifier as a method for measuring radical concentrations in the atmosphere has received renewed attention lately. In principle, it can measure the total concentration of HO(x) and RO(x) radicals by reacting ambient air with high concentrations of CO (3-10 percent) and NO (2-6 ppmv), and measuring the NO2 produced.

Hastie, D. R.↗
NASA NTRS1979

Boundary layer measurements of the OH radical in the vicinity of an isolated power plant plume - SO2 and NO2 chemical conversion times

Direct measurements of the OH radical in the vicinity of an isolated power plant plume are reported. These measurements were used to estimate the conversion time of SO2 to H2SO4-sulfate aerosol via the initiating step OH + SO2 + M yields HSO3. Using the near-high-noon measured value of OH (9.5 million per cu cm), resulted in a 1/e conversion time of 1.4 days. The latter lifetime would correspond to a conversion rate of about 2%/hr. When the lifetime calculation was modified to take into consideration the OH diurnal cycle, the 1/e conversion time for SO2 was found to be 4.4 days, giving an apparent overall rate of conversion of about 0.7%/hr. Similar calculations carried out for the conversion of NO2 to NHO3 resulted in 1/e lifetimes for NO2 of 2-3 h for midday time periods.

Davis, D. D.↗
DOE OSTI2020

Materials Data on ZnH8(NO2)6 by Materials Project

Zn(NO3)4(NH4)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of eight ammonium molecules and four Zn(NO3)4 clusters. In two of the Zn(NO3)4 clusters, Zn2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Zn–O bond distances ranging from 2.06–2.36 Å. There are four inequivalent N+2.33+ sites. In the first N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.25–1.30 Å. In the second N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.29 Å. In the third N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.23–1.30 Å. In the fourth N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.33 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the second O2- site, O2- is bonded in an L-shaped geometry to one Zn2+ and one N+2.33+ atom. In the third O2- site, O2- is bonded in a distorted L-shaped geometry to one Zn2+ and one N+2.33+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the fifth O2- site, O2- is bonded in a distorted L-shaped geometry to one Zn2+ and one N+2.33+ atom. In the sixth O2- site, O2- is bonded in a water-like geometry to one Zn2+ and one N+2.33+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one N+2.33+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the eleventh O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one N+2.33+ atom. In two of the Zn(NO3)4 clusters, Zn2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Zn–O bond distances ranging from 2.02–2.78 Å. There are four inequivalent N+2.33+ sites. In the first N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.31 Å. In the second N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.25 Å) and one longer (1.30 Å) N–O bond length. In the third N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.30 Å. In the fourth N+2.33+ site, N+2.33+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.30 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted L-shaped geometry to one Zn2+ and one N+2.33+ atom. In the second O2- site, O2- is bonded in an L-shaped geometry to one Zn2+ and one N+2.33+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Zn2+ and one N+2.33+ atom. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one N+2.33+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one Zn2+ and one N+2.33+ atom. In the eighth O2- site, O2- is bonded in a water-like geometry to one Zn2+ and one N+2.33+ atom. In the ninth O2- site, O2- is bonded in a water-like geometry to one Zn2+ and one N+2.33+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one Zn2+ and one N+2.33+ atom. In the twelfth O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1995

An overview of the SABER experiment for the TIMED mission

The Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) experiment has been selected for flight on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) mission expected to fly in the latter part of this decade. The primary science goal of SABER is to achieve fundamental and important advances in understanding of the energetics, chemistry, and dynamics, in the atmospheric region extending from 60 km to 180 km altitude, which has not been comprehensively observed on a global basis. This will be accomplished using the space flight proven experiment approach of broad spectral band limb emission radiometry. SABER will scan the horizon in 12 selected bands ranging from 1.27 microns to 17 microns wavelength. The observed vertical horizon emission profiles will be mathematically inverted in ground data processing to provide vertical profiles with 2 km vertical resolution, of temperature, O3, H2O, NO, NO2, CO, and CO2. SABER will also observe key emissions needed for energetics studies at 1.27 microns (O2((sup 1)delta)), 2 microns (OH(v = 7,8,9)) 1.6 microns (OH(v = 3,4,5)), 4.3 microns (CO2(v(sub 3))) 5.3 microns (NO) 9.6 microns (O3), and 15 microns (CO2(v(sub 2))). These measurements will be used to infer atomic hydrogen and atomic oxygen, the latter inferred three different ways using only SABER observations. Measurements will be made both night and day over the latitude range from the southern to northern polar regions.

Mlynczak, Martin G.↗
NASA NTRS2018

Top-Down NOx Emissions of European Cities Based on the Downwind Plume of Modelled and Space-Borne Tropospheric NO2 Columns

Top-down estimates of surface NOX emissions were derived for 23 European cities based on the downwind plume decay of tropospheric nitrogen dioxide (NO2) columns from the LOTOS-EUROS (Long Term Ozone Simulation-European Ozone Simulation) chemistry transport model (CTM) and from Ozone Monitoring Instrument (OMI) satellite retrievals, averaged for the summertime period (April-September) during 2013. Here we show that the top-down NOX emissions derived from LOTOS-EUROS for European urban areas agree well with the bottom-up NOX emissions from the MACC-III inventory data (R(exp 2) = 0.88) driving the CTM demonstrating the potential of this method. OMI top-down NOX emissions over the 23 European cities are generally lower compared with the MACC-III emissions and their correlation is slightly lower (R(exp 2) = 0.79). The uncertainty on the derived NO2 lifetimes and NOX emissions are on average ~55% for OMI and ~63% for LOTOS-EUROS data. The downwind NO2 plume method applied on both LOTOS-EUROS and OMI tropospheric NO2 columns allows to estimate NOX emissions from urban areas, demonstrating that this is a useful method for real-time updates of urban NOX emissions with reasonable accuracy.

NOx emissions↗
NASA NTRS2020

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

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.

NO2↗
NASA NTRS1994

Stratospheric OClO and NO2 measured by groundbased UV/Vis-spectroscopy in Greenland in January and February 1990 and 1991

Groundbased UV/Vis-spectroscopy of zenith scattered sunlight was performed at Sondre Stromfjord (Greenland) during Jan/Feb 1990 and Jan/Feb 1991. Considerable amounts of OClO were observed during both campaigns. Maximum OClO vertical column densities at 92 deg solar zenith angle (SZA) were 7.4 x 10(exp 13) molec/sq cm in 1990 and 5.7 x 10(exp 13) molec/sq cm in 1991 (chemical enhancement is included in the calculation of the air mass factor (AMF)). A threshold seems to exist for OClO detection: OClO was detected on every day when the potential vorticity at the 475 K level of potential temperature was higher than 35 x 10(exp -6)Km(exp 2)kg(exp -1)s(exp -1). NO2 vertical columns lower than 1 x 10(exp 15) molec/sq cm were frequently observed in both winters.

Roth, A.↗
DOE OSTI2020

Near-Zero Power MOF-Based Sensors for NO 2 Detection

Detection and capture of toxic nitrogen oxides (NO x ) is important for emissions control of exhaust gases and general public health. The ability to directly electrically detect trace (0.5–5 ppm) NO 2 by a metal–organic framework (MOF)-74-based sensor at relatively low temperatures (50 °C) is demonstrated via changes in electrical properties of M-MOF-74, M = Co, Mg, Ni. The magnitude of the change is ordered Ni > Co > Mg and explained by each variant's NO 2 adsorption capacity and specific chemical interaction. Ni-MOF-74 provides the highest sensitivity to NO 2 ; a 725× decrease in resistance at 5 ppm NO2 and detection limit <0.5 ppm, levels relevant for industry and public health. Furthermore, the Ni-MOF-74-based sensor is selective to NO 2 over N 2 , SO 2 , and air. Linking this fundamental research with future technologies, the high impedance of MOF-74 enables applications requiring a near-zero power sensor or dosimeter, with the active material drawing <15 pW for a macroscale device 35 mm 2 with 0.8 mg MOF-74. Finally, this represents a 10 4 –10 6 × decrease in power consumption compared to other MOF sensors and demonstrates the potential for MOFs as active components for long-lived, near-zero power chemical sensors in smart industrial systems and the internet of things.

47 OTHER INSTRUMENTATION↗
NASA NTRS2021

Reductions in NO2 Burden Over North Equatorial Africa from Decline in Biomass Burning in Spite of Growing Fossil Fuel Use, 2005 to 2017

Socioeconomic development in low- and middle-income countries has been accompanied by increased emissions of air pollutants, such as nitrogen oxides [NOx: nitrogen dioxide (NO2) + nitric oxide (NO)], which affect human health. In sub-Saharan Africa, fossil fuel combustion has nearly doubled since 2000. At the same time, landscape biomass burning—another important NOx source—has declined in north equatorial Africa, attributed to changes in climate and anthropogenic fire management. Here, we use satellite observations of tropospheric NO2 vertical column densities (VCDs) and burned area to identify NO2 trends and drivers over Africa. Across the northern ecosystems where biomass burning occurs—home to hundreds of millions of people—mean annual tropospheric NO2 VCDs decreased by 4.5% from 2005 through 2017 during the dry season of November through February. Reductions in burned area explained the majority of variation in NO2 VCDs, though changes in fossil fuel emissions also explained some variation. Over Africa’s biomass burning regions, raising mean GDP density (USD·km−2) above its lowest levels is associated with lower NO2 VCDs during the dry season, suggesting that economic development mitigates net NO2 emissions during these highly polluted months. In contrast to the traditional notion that socioeconomic development increases air pollutant concentrations in low- and middle-income nations, our results suggest that countries in Africa’s northern biomass-burning region are following a different pathway during the fire season, resulting in potential air quality benefits. However, these benefits may be lost with increasing fossil fuel use and are absent during the rainy season.

air pollution↗
NASA NTRS1994

Balloon profiles of stratospheric NO2 and HNO3 for testing the heterogeneous hydrolysis of N2O5 on sulfate aerosols

Simultaneous in situ measurements of stratospheric NO2, HNO3, HCl, and CH4 from 34 to 24 km were made in August 1992 from Palestine, Texas, using the Balloon-borne Laser In-Situ Sensor (BLISS) tunable diode laser spectrometer. Although the measurements of NO2, HNO3, and NO2/HNO3 agree well with gas-phase model calculations near 34 km where Stratospheric Aerosol and Gas Experiment (SAGE) 2 data show little sulfate aerosol, this is not true at the lower altitudes where SAGE 2 shows high aerosol loadings. At 24 km the BLISS NO2 and HNO3 measurements are 70% lower and 50% higher, respectively, than the gas phase model predictions, with a measured NO2/HNO3 ratio 5 times smaller. When the heterogeneous hydrolysis of N2O5 and ClONO2 on sulfate aerosol of surface area densities matching the SAGE 2 measurements is added to the model, good agreement with the BLISS measurements is found over the whole altitude range.

Webster, C. R.↗
NASA NTRS1990

Observed and model-calculated NO2/NO ratios in tropospheric air sampled during the NASA GTE/CITE-2 field study

Airborne measurements of NO2/NO ratios in the free troposphere, obtained using two-photon LIF (TP-LIF) and chemiluminescence (CL) detectors during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986, are analyzed and compared with the predictions of a photochemical model. The derivation of the model is outlined, with an emphasis on the role of peroxy radicals in the fast photochemical cycling of NO and NO2 and the production of O3; the CITE 2 instruments and flight protocols are described; and the results are presented in extensive tables and graphs and discussed in detail. It was found that on three CITE 2 flights the CL data were systematically greater than the TP-LIF data; when these data were removed, the averaged values of the two instruments agreed to within 1 percent. The NO2/NO ratios predicted by the model are shown to be consistent with the measurements, although usually 20-25 percent lower.

Chameides, W. L.↗
NASA NTRS2007

OMI Total and Tropospheric Column Nitrogen Dioxide: Version 2 Status

The at-launch version of the OM1 NO2 total and tropospheric NO2 algorithm made a number of assumptions about instrument performance. Our knowledge of tropospheric NO2 has increased in the 3 years since the inital version was delivered. The results of the post-launch validation campaigns and improved atmospheric modelling has lead to changes in the NO2 retrieval algorithm. The algorithm changes and the impacts on the data products will be presented.

Gleason, James↗
NASA NTRS2020

Assessment of NO2 Observations During DISCOVER-AQ and KORUS-AQ Field Campaigns

NASA’s Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011–2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea–United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated data sets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO2), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO2 measurements were made, including in situ concentrations and column amounts of NO2 using ground- and aircraft-based instruments, while NO2 column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO2 simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models. We then use these data to interpret observed discrepancies due to differences in sampling and deficiencies in the data reduction process. Finally, we assess satellite retrieval sensitivity to observed and modeled a priori NO2 profiles. Contemporaneous measurements from two aircraft instruments that likely sample similar air masses generally agree very well but are also found to differ in integrated columns by up to 31.9 %. These show even larger differences with Pandora, reaching up to 53.9 %, potentially due to a combination of strong gradients in NO2 fields that could be missed by aircraft spirals and errors in the Pandora retrievals. OMI NO2 values are about a actor of 2 lower in these highly polluted environments due in part to inaccurate retrieval assumptions (e.g., a priori pro-files) but mostly to OMI’s large footprint (>312 km2).

Nitrogen dioxide↗