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Observing Nitrogen Dioxide Air Pollution Inequality Using High-Spatial-Resolution Remote Sensing Measurements in Houston, TexasDemetillo, Mary Angelique G.Navarro, AracelyKnowles, Katherine K.Fields, Kimberly P.Geddes, Jeffrey A.Nowlan, Caroline R.Janz, Scott J.Judd, Laura M.Al-Saadi, JassimSun, KangMcDonald, Brian C.Diskin, Glenn S.Pusede, Sally E.DOI: info:10.1021/acs.est.0c01864v. 54No. 169882–9895
Demetillo, Mary Angelique G., Navarro, Aracely, Knowles, Katherine K., Fields, Kimberly P., Geddes, Jeffrey A., Nowlan, Caroline R., Janz, Scott J., Judd, Laura M., Al-Saadi, Jassim, Sun, Kang, McDonald, Brian C., Diskin, Glenn S., and Pusede, Sally E. 2020. "Observing Nitrogen Dioxide Air Pollution Inequality Using High-Spatial-Resolution Remote Sensing Measurements in Houston, Texas." Environmental science & technology 54 (16):9882– 9895. https://doi.org/10.1021/acs.est.0c01864
ID: 156692
Type: article
Authors: Demetillo, Mary Angelique G.; Navarro, Aracely; Knowles, Katherine K.; Fields, Kimberly P.; Geddes, Jeffrey A.; Nowlan, Caroline R.; Janz, Scott J.; Judd, Laura M.; Al-Saadi, Jassim; Sun, Kang; McDonald, Brian C.; Diskin, Glenn S.; Pusede, Sally E.
Evaluating Sentinel-5P TROPOMI tropospheric NO2 column densities with airborne and Pandora spectrometers near New York City and Long Island SoundJudd, Laura M.Al-Saadi, Jassim A.Szykman, James J.Valin, Lukas C.Janz, Scott J.Kowalewski, Matthew G.Eskes, Henk J.Pepijn Veefkind, J.Cede, AlexanderMueller, MoritzGebetsberger, ManuelSwap, RobertPierce, R. BradleyNowlan, Caroline R.González Abad, GonzaloNehrir, AminWilliams, DavidDOI: info:10.5194/amt-13-6113-2020v. 136113–6140
Judd, Laura M., Al-Saadi, Jassim A., Szykman, James J., Valin, Lukas C., Janz, Scott J., Kowalewski, Matthew G., Eskes, Henk J., Pepijn Veefkind, J., Cede, Alexander, Mueller, Moritz, Gebetsberger, Manuel, Swap, Robert, Pierce, R. Bradley, Nowlan, Caroline R., González Abad, Gonzalo, Nehrir, Amin, and Williams, David. 2020. "Evaluating Sentinel-5P TROPOMI tropospheric NO2 column densities with airborne and Pandora spectrometers near New York City and Long Island Sound." Atmospheric Measurement Techniques 13:6113– 6140. https://doi.org/10.5194/amt-13-6113-2020
ID: 158802
Type: article
Authors: Judd, Laura M.; Al-Saadi, Jassim A.; Szykman, James J.; Valin, Lukas C.; Janz, Scott J.; Kowalewski, Matthew G.; Eskes, Henk J.; Pepijn Veefkind, J.; Cede, Alexander; Mueller, Moritz; Gebetsberger, Manuel; Swap, Robert; Pierce, R. Bradley; Nowlan, Caroline R.; González Abad, Gonzalo; Nehrir, Amin; Williams, David
Abstract: Airborne and ground-based Pandora spectrometer NO2 column measurements were collected during the 2018 Long Island Sound Tropospheric Ozone Study (LISTOS) in the New York City/Long Island Sound region, which coincided with early observations from the Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) instrument. Both airborne- and ground-based measurements are used to evaluate the TROPOMI NO2 Tropospheric Vertical Column (TrVC) product v1.2 in this region, which has high spatial and temporal heterogeneity in NO2. First, airborne and Pandora TrVCs are compared to evaluate the uncertainty of the airborne TrVC and establish the spatial representativeness of the Pandora observations. The 171 coincidences between Pandora and airborne TrVCs are found to be highly correlated (r2= 0.92 and slope of 1.03), with the largest individual differences being associated with high temporal and/or spatial variability. These reference measurements (Pandora and airborne) are complementary with respect to temporal coverage and spatial representativity. Pandora spectrometers can provide continuous long-term measurements but may lack areal representativity when operated in direct-sun mode. Airborne spectrometers are typically only deployed for short periods of time, but their observations are more spatially representative of the satellite measurements with the added capability of retrieving at subpixel resolutions of 250 m × 250 m over the entire TROPOMI pixels they overfly. Thus, airborne data are more correlated with TROPOMI measurements (r2=0.96) than Pandora measurements are with TROPOMI (r2=0.84). The largest outliers between TROPOMI and the reference measurements appear to stem from too spatially coarse a priori surface reflectivity (0.5°) over bright urban scenes. In this work, this results during cloud-free scenes that, at times, are affected by errors in the TROPOMI cloud pressure retrieval impacting the calculation of tropospheric air mass factors. This factor causes a high bias in TROPOMI TrVCs of 4 %-11 %. Excluding these cloud-impacted points, TROPOMI has an overall low bias of 19 %-33 % during the LISTOS timeframe of June-September 2018. Part of this low bias is caused by coarse a priori profile input from the TM5-MP model; replacing these profiles with those from a 12 km North American Model-Community Multiscale Air Quality (NAMCMAQ) analysis results in a 12 %-14 % increase in the TrVCs. Even with this improvement, the TROPOMI-NAMCMAQ TrVCs have a 7 %-19 % low bias, indicating needed improvement in a priori assumptions in the air mass factor calculation. Future work should explore additional impacts of a priori inputs to further assess the remaining low biases in TROPOMI using these datasets.
An inversion of NOx and non-methane volatile organic compound (NMVOC) emissions using satellite observations during the KORUS-AQ campaign and implications for surface ozone over East AsiaSouri, Amir H.Nowlan, Caroline R.González Abad, GonzaloZhu, LeiBlake, Donald R.Fried, AlanWeinheimer, Andrew J.Wisthaler, ArminWoo, Jung-HunZhang, QiangMiller, Christopher E. ChanLiu, XiongChance, KellyDOI: info:10.5194/acp-20-9837-2020v. 209837–9854
Souri, Amir H., Nowlan, Caroline R., González Abad, Gonzalo, Zhu, Lei, Blake, Donald R., Fried, Alan, Weinheimer, Andrew J., Wisthaler, Armin, Woo, Jung-Hun, Zhang, Qiang, Miller, Christopher E. Chan, Liu, Xiong, and Chance, Kelly. 2020. "An inversion of NOx and non-methane volatile organic compound (NMVOC) emissions using satellite observations during the KORUS-AQ campaign and implications for surface ozone over East Asia." Atmospheric Chemistry & Physics 20:9837– 9854. https://doi.org/10.5194/acp-20-9837-2020
ID: 158080
Type: article
Authors: Souri, Amir H.; Nowlan, Caroline R.; González Abad, Gonzalo; Zhu, Lei; Blake, Donald R.; Fried, Alan; Weinheimer, Andrew J.; Wisthaler, Armin; Woo, Jung-Hun; Zhang, Qiang; Miller, Christopher E. Chan; Liu, Xiong; Chance, Kelly
Abstract: The absence of up-to-date emissions has been a major impediment to accurately simulating aspects of atmospheric chemistry and to precisely quantifying the impact of changes in emissions on air pollution. Hence, a nonlinear joint analytical inversion (Gauss-Newton method) of both volatile organic compounds (VOCs) and nitrogen oxide (NOx) emissions is made by exploiting the Smithsonian Astrophysical Observatory (SAO) Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) formaldehyde (HCHO) and the National Aeronautics and Space Administration (NASA) Ozone Monitoring Instrument (OMI) tropospheric nitrogen dioxide (NO2) columns during the Korea-United States Air Quality (KORUS-AQ) campaign over East Asia in May-June 2016. Effects of the chemical feedback of NOx and VOCs on both NO2 and HCHO are implicitly included by iteratively optimizing the inversion. Emission uncertainties are greatly narrowed (averaging kernels > 0.8, which is the mathematical presentation of the partition of information gained from the satellite observations with respect to the prior knowledge) over medium- to high-emitting areas such as cities and dense vegetation. The prior amount of total NOx emissions is mainly dictated by values reported in the MIX-Asia 2010 inventory. After the inversion we conclude that there is a decline in emissions (before, after, change) for China (87.94±44.09 Gg d-1, 68.00±15.94 Gg d-1, -23 %), North China Plain (NCP) (27.96±13.49 Gg d-1, 19.05±2.50 Gg d-1, -32 %), Pearl River Delta (PRD) (4.23±1.78 Gg d-1, 2.70±0.32 Gg d-1, -36 %), Yangtze River Delta (YRD) (9.84±4.68 Gg d-1, 5.77±0.51 Gg d-1, -41 %), Taiwan (1.26±0.57 Gg d-1, 0.97±0.33 Gg d-1, -23 %), and Malaysia (2.89±2.77 Gg d-1, 2.25±1.34 Gg d-1, -22 %), all of which have effectively implemented various stringent regulations. In contrast, South Korea (2.71±1.34 Gg d-1, 2.95±0.58 Gg d-1, +9 %) and Japan (3.53±1.71 Gg d-1, 3.96±1.04 Gg d-1, +12 %) are experiencing an increase in NOx emissions, potentially due to an increased number of diesel vehicles and new thermal power plants. We revisit the well-documented positive bias (by a factor of 2 to 3) of MEGAN v2.1 (Model of Emissions of Gases and Aerosols from Nature) in terms of biogenic VOC emissions in the tropics. The inversion, however, suggests a larger growth of VOCs (mainly anthropogenic) over NCP (25 %) than previously reported (6 %) relative to 2010. The spatial variation in both the magnitude and sign of NOx and VOC emissions results in nonlinear responses of ozone production and loss. Due to a simultaneous decrease and increase in NOx/VOC over NCP and YRD, we observe a ∼53 % reduction in the ratio of the chemical loss of NOx (LNOx) to the chemical loss of ROx (RO2+HO2) over the surface transitioning toward NOx-sensitive regimes, which in turn reduces and increases the afternoon chemical loss and production of ozone through NO2+OH (-0.42 ppbv h-1)/HO2 (and RO2)+NO (+0.31 ppbv h-1). Conversely, a combined decrease in NOx and VOC emissions in Taiwan, Malaysia, and southern China suppresses the formation of ozone. Simulations using the updated emissions indicate increases in maximum daily 8 h average (MDA8) surface ozone over China (0.62 ppbv), NCP (4.56 ppbv), and YRD (5.25 ppbv), suggesting that emission control strategies on VOCs should be prioritized to curb ozone production rates in these regions. Taiwan, Malaysia, and PRD stand out as regions undergoing lower MDA8 ozone levels resulting from the NOx reductions occurring predominantly in NOx-sensitive regimes.
Corrigendum to 'Revisiting the effectiveness of HCHO/NO2 ratios for inferring ozone sensitivity to its precursors using high resolution airborne remote sensing observations in a high ozone episode during the KORUS-AQ campaign' [Atmos. Environ. 224 117341]Souri, Amir H.Nowlan, Caroline R.Wolfe, Glenn M.Lamsal, Lok N.Chan Miller, Christopher E.González Abad, GonzaloJanz, Scott J.Fried, AlanBlake, Donald R.Weinheimer, Andrew J.Diskin, Glenn S.Liu, XiongChance, KellyDOI: info:10.1016/j.atmosenv.2020.117792v. 240117792
Souri, Amir H., Nowlan, Caroline R., Wolfe, Glenn M., Lamsal, Lok N., Chan Miller, Christopher E., González Abad, Gonzalo, Janz, Scott J., Fried, Alan, Blake, Donald R., Weinheimer, Andrew J., Diskin, Glenn S., Liu, Xiong, and Chance, Kelly. 2020. "Corrigendum to "Revisiting the effectiveness of HCHO/NO2 ratios for inferring ozone sensitivity to its precursors using high resolution airborne remote sensing observations in a high ozone episode during the KORUS-AQ campaign" [Atmos. Environ. 224 117341]." Atmospheric Environment 240:117792. https://doi.org/10.1016/j.atmosenv.2020.117792
ID: 157460
Type: article
Authors: Souri, Amir H.; Nowlan, Caroline R.; Wolfe, Glenn M.; Lamsal, Lok N.; Chan Miller, Christopher E.; González Abad, Gonzalo; Janz, Scott J.; Fried, Alan; Blake, Donald R.; Weinheimer, Andrew J.; Diskin, Glenn S.; Liu, Xiong; Chance, Kelly
Abstract: The authors regret both Fig. S2 and Fig. S3 were inadvertently used a wrong day (06/10 instead of 06/09 due to a difference in the UTC vs local times) for plotting the NASA's LaRC box model output. The new figure shows that both F0AM and LaRC models are in a strong degree of agreement (<10%) suggesting that the non-linear ozone chemistry over Seoul can be reasonably represented by both models. This correction does not impact the conclusion drawn from this study. We thank James H. Crawford for pointing us at the bug.
Revisiting the effectiveness of HCHO/NO2 ratios for inferring ozone sensitivity to its precursors using high resolution airborne remote sensing observations in a high ozone episode during the KORUS-AQ campaignSouri, Amir HosseinNowlan, Caroline R.Wolfe, Glenn M.Lamsal, Lok N.Chan Miller, Christopher E.Abad, Gonzalo GonzálezJanz, Scott J.Fried, AlanBlake, Donald R.Weinheimer, Andrew J.Diskin, Glenn S.Liu, XiongChance, KellyDOI: info:10.1016/j.atmosenv.2020.117341v. 224117341
Souri, Amir Hossein, Nowlan, Caroline R., Wolfe, Glenn M., Lamsal, Lok N., Chan Miller, Christopher E., Abad, Gonzalo González, Janz, Scott J., Fried, Alan, Blake, Donald R., Weinheimer, Andrew J., Diskin, Glenn S., Liu, Xiong, and Chance, Kelly. 2020. "Revisiting the effectiveness of HCHO/NO2 ratios for inferring ozone sensitivity to its precursors using high resolution airborne remote sensing observations in a high ozone episode during the KORUS-AQ campaign." Atmospheric Environment 224:117341. https://doi.org/10.1016/j.atmosenv.2020.117341
ID: 156335
Type: article
Authors: Souri, Amir Hossein; Nowlan, Caroline R.; Wolfe, Glenn M.; Lamsal, Lok N.; Chan Miller, Christopher E.; Abad, Gonzalo González; Janz, Scott J.; Fried, Alan; Blake, Donald R.; Weinheimer, Andrew J.; Diskin, Glenn S.; Liu, Xiong; Chance, Kelly
Abstract: The nonlinear chemical processes involved in ozone production (P(O3)) have necessitated using proxy indicators to convey information about the primary dependence of P(O3) on volatile organic compounds (VOCs) or nitrogen oxides (NOx). In particular, the ratio of remotely sensed columns of formaldehyde (HCHO) to nitrogen dioxide (NO2) has been widely used for studying O3 sensitivity. Previous studies found that the errors in retrievals and the incoherent relationship between the column and the near-surface concentrations are a barrier in applying the ratio in a robust way. In addition to these obstacles, we provide calculational- observational evidence, using an ensemble of 0-D photochemical box models constrained by DC-8 aircraft measurements on an ozone event during the Korea-United States Air Quality (KORUS-AQ) campaign over Seoul, to demonstrate the chemical feedback of NO2 on the formation of HCHO is a controlling factor for the transition line between NOx-sensitive and NOx-saturated regimes. A fixed value (~2.7) of the ratio of the chemical loss of NOx (LNOx) to the chemical loss of HO2+RO2 (LROx) perceptibly differentiates the regimes. Following this value, data points with a ratio of HCHO/NO2 less than 1 can be safely classified as NOx-saturated regime, whereas points with ratios between 1 and 4 fall into one or the other regime. We attribute this mainly to the HCHO-NO2 chemical relationship causing the transition line to occur at larger (smaller) HCHO/NO2 ratios in VOC-rich (VOC-poor) environments. We then redefine the transition line to LNOx/LROx~2.7 that accounts for the HCHO-NO2 chemical relationship leading to HCHO = 3.7 × (NO2 - 1.14 × 1016 molec.cm-2). Although the revised formula is locally calibrated (i.e., requires for readjustment for other regions), its mathematical format removes the need for having a wide range of thresholds used in HCHO/NO2 ratios that is a result of the chemical feedback. Therefore, to be able to properly take the chemical feedback into consideration, the use of HCHO = a × (NO2 - b) formula should be preferred to the ratio in future works. We then use the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument to study O3 sensitivity in Seoul. The unprecedented spatial (250 × 250 m2) and temporal (~every 2 h) resolutions of HCHO and NO2 observations form the sensor enhance our understanding of P(O3) in Seoul; rather than providing a crude label for the entire city, more in-depth variabilities in chemical regimes are observed that should be able to inform mitigation strategies correspondingly.
Validation of satellite formaldehyde (HCHO) retrievals using observations from 12 aircraft campaignsZhu, LeiAbad, Gonzalo GonzalezNowlan, Caroline R.Miller, Christopher ChanChance, KellyApel, Eric C.DiGangi, Joshua P.Fried, AlanHanisco, Thomas F.Hornbrook, Rebecca S.Hu, LuKaiser, JenniferKeutsch, Frank N.Permar, WadeSt Clair, Jason M.Wolfe, Glenn M.DOI: info:10.5194/acp-20-12329-2020v. 20No. 2012329–12345
Zhu, Lei, Abad, Gonzalo Gonzalez, Nowlan, Caroline R., Miller, Christopher Chan, Chance, Kelly, Apel, Eric C., DiGangi, Joshua P., Fried, Alan, Hanisco, Thomas F., Hornbrook, Rebecca S., Hu, Lu, Kaiser, Jennifer, Keutsch, Frank N., Permar, Wade, St Clair, Jason M., and Wolfe, Glenn M. 2020. "Validation of satellite formaldehyde (HCHO) retrievals using observations from 12 aircraft campaigns." Atmospheric Chemistry and Physics 20 (20):12329– 12345. https://doi.org/10.5194/acp-20-12329-2020
ID: 157528
Type: article
Authors: Zhu, Lei; Abad, Gonzalo Gonzalez; Nowlan, Caroline R.; Miller, Christopher Chan; Chance, Kelly; Apel, Eric C.; DiGangi, Joshua P.; Fried, Alan; Hanisco, Thomas F.; Hornbrook, Rebecca S.; Hu, Lu; Kaiser, Jennifer; Keutsch, Frank N.; Permar, Wade; St Clair, Jason M.; Wolfe, Glenn M.
Abstract: Formaldehyde (HCHO) has been measured from space for more than 2 decades. Owing to its short atmospheric lifetime, satellite HCHO data are used widely as a proxy of volatile organic compounds (VOCs; please refer to Appendix A for abbreviations and acronyms), providing constraints on underlying emissions and chemistry. However, satellite HCHO products from different satellite sensors using different algorithms have received little validation so far. The accuracy and consistency of HCHO retrievals remain largely unclear. Here we develop a validation platform for satellite HCHO retrievals using in situ observations from 12 aircraft campaigns with a chemical transport model (GEOS-Chem) as the intercomparison method. Application to the NASA operational OMI HCHO product indicates negative biases (- 44.5 % to -21.7 %) under high-HCHO conditions, while it indicates high biases (+66.1 % to +112.1 %) under low-HCHO conditions. Under both conditions, HCHO a priori vertical profiles are likely not the main driver of the biases. By providing quick assessment of systematic biases in satellite products over large domains, the platform facilitates, in an iterative process, optimization of retrieval settings and the minimization of retrieval biases. It is also complementary to localized validation efforts based on ground observations and aircraft spirals.
Five decades observing Earth's atmospheric trace gases using ultraviolet and visible backscatter solar radiation from spaceGonzalez Abad, GonzaloSouri, Amir HosseinBak, JuseonChance, KellyFlynn, Lawrence E.Krotkov, Nickolay A.Lamsal, LokLi, CanLiu, XiongChan Miller, ChristopherNowlan, Caroline R.Suleiman, RaidWang, HuiqunDOI: info:10.1016/j.jqsrt.2019.04.030v. 238106478
Gonzalez Abad, Gonzalo, Souri, Amir Hossein, Bak, Juseon, Chance, Kelly, Flynn, Lawrence E., Krotkov, Nickolay A., Lamsal, Lok, Li, Can, Liu, Xiong, Chan Miller, Christopher, Nowlan, Caroline R., Suleiman, Raid, and Wang, Huiqun. 2019. "Five decades observing Earth's atmospheric trace gases using ultraviolet and visible backscatter solar radiation from space." Journal of Quantitative Spectroscopy and Radiative Transfer 238:106478. https://doi.org/10.1016/j.jqsrt.2019.04.030
ID: 154602
Type: article
Authors: Gonzalez Abad, Gonzalo; Souri, Amir Hossein; Bak, Juseon; Chance, Kelly; Flynn, Lawrence E.; Krotkov, Nickolay A.; Lamsal, Lok; Li, Can; Liu, Xiong; Chan Miller, Christopher; Nowlan, Caroline R.; Suleiman, Raid; Wang, Huiqun
Abstract: Over the last five decades, Earth's atmosphere has been extensively monitored from space using different spectral ranges. Early efforts were directed at improving weather forecasts with the first meteorological satellites launched in the 1960s. Soon thereafter, the intersection between weather, climate and atmospheric chemistry led to the observation of atmospheric composition from space. During the 1970s the Nimbus satellite program started regular monitoring of ozone integrated columns and water vapor profiles using the Backscatter Ultraviolet Spectrometer, the Infrared Interferometer Spectrometer and the Satellite Infrared Spectrometer instruments. Five decades after these pioneer efforts, continuous progress in instrument design, and retrieval techniques allow researchers to monitor tropospheric concentrations of a wide range of species with implications for air quality, climate and weather. The time line of historic, present and future space-borne instruments measuring ultraviolet and visible backscattered solar radiation designed to quantify atmospheric trace gases is presented. We describe the instruments technological evolution and the basic concepts of retrieval theory. We include a review of algorithms developed for ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, bromine monoxide, water vapor and glyoxal, a selection of studies using these algorithms, the challenges they face and how these challenges can be addressed. The paper ends by providing insights on the opportunities that new instruments will bring to the atmospheric chemistry, weather and air quality communities and how to address the pressing need for long-term, inter-calibrated data records necessary to monitor the response of the atmosphere to rapidly changing ecosystems.
Explicit Aerosol Correction of OMI Formaldehyde RetrievalsJung, YeonjinGonzález Abad, GonzaloNowlan, Caroline R.Chance, KellyLiu, XiongTorres, OmarAhn, ChangwooDOI: info:10.1029/2019EA000702v. 62087–2105
Jung, Yeonjin, González Abad, Gonzalo, Nowlan, Caroline R., Chance, Kelly, Liu, Xiong, Torres, Omar, and Ahn, Changwoo. 2019. "Explicit Aerosol Correction of OMI Formaldehyde Retrievals." Earth and Space Science 6:2087– 2105. https://doi.org/10.1029/2019EA000702
ID: 155115
Type: article
Authors: Jung, Yeonjin; González Abad, Gonzalo; Nowlan, Caroline R.; Chance, Kelly; Liu, Xiong; Torres, Omar; Ahn, Changwoo
Abstract: Atmospheric aerosols are significant sources of uncertainty in air mass factor (AMF) calculations for trace gas retrievals using ultraviolet measurements from space. Current trace gas retrievals typically do not consider aerosols explicitly as cloud products partially account for aerosol effects. Here, we propose a new measurement-based approach to correct for aerosols explicitly in the AMF calculation, apply it to Ozone Monitoring Instrument (OMI) formaldehyde (HCHO) retrievals and quantify the aerosol-induced HCHO vertical column density difference for three aerosol types (smoke, dust, and sulfate) during 2006-2007. We use OMI aerosol retrievals for aerosol optical properties and vertical profiles to construct lookup tables of scattering weights as functions of geometry, surface pressure, surface albedo, and aerosol information. The average difference between the National Aeronautics and Space Administration operational OMI HCHO product (not considering aerosols) and the results obtained in this study on a global scale are 27%, 6%, and -0.3% for smoke, dust, and sulfate aerosols, respectively. The region with the largest aerosol effects is East China, where the explicit smoke aerosol correction enhances mean HCHO vertical column densities by 35%, with corrections to individual observations sometimes larger than 100%. The quantified aerosol effects are applicable under clear-sky conditions. This study highlights the need to implement aerosol corrections in the AMF calculation for HCHO retrievals. This is particularly relevant in regions with high levels of pollution where aerosols interfere the most with formaldehyde satellite observations.
Characterization of the OCO-2 instrument line shape functions using on-orbit solar measurementsSun, KangLiu, XiongNowlan, Caroline R.Cai, ZhaonanChance, Kelly V.Frankenberg, ChristianLee, Richard A. M.Pollock, RandyRosenberg, RobertCrisp, DavidDOI: info:10.5194/amt-10-939-2017v. 10939–953
Sun, Kang, Liu, Xiong, Nowlan, Caroline R., Cai, Zhaonan, Chance, Kelly V., Frankenberg, Christian, Lee, Richard A. M., Pollock, Randy, Rosenberg, Robert, and Crisp, David. 2017. "Characterization of the OCO-2 instrument line shape functions using on-orbit solar measurements." Atmospheric Measurement Techniques 10:939– 953. https://doi.org/10.5194/amt-10-939-2017
ID: 142859
Type: article
Authors: Sun, Kang; Liu, Xiong; Nowlan, Caroline R.; Cai, Zhaonan; Chance, Kelly V.; Frankenberg, Christian; Lee, Richard A. M.; Pollock, Randy; Rosenberg, Robert; Crisp, David
Abstract: Accurately characterizing the instrument line shape (ILS) of the Orbiting Carbon Observatory-2 (OCO-2) is challenging and highly important due to its high spectral resolution and requirement for retrieval accuracy (0. 25 %) compared to previous spaceborne grating spectrometers. On-orbit ILS functions for all three bands of the OCO-2 instrument have been derived using its frequent solar measurements and high-resolution solar reference spectra. The solar reference spectrum generated from the 2016 version of the Total Carbon Column Observing Network (TCCON) solar line list shows significant improvements in the fitting residual compared to the solar reference spectrum currently used in the version 7 Level 2 algorithm in the O2 A band. The analytical functions used to represent the ILS of previous grating spectrometers are found to be inadequate for the OCO-2 ILS. Particularly, the hybrid Gaussian and super-Gaussian functions may introduce spurious variations, up to 5 % of the ILS width, depending on the spectral sampling position, when there is a spectral undersampling. Fitting a homogeneous stretch of the preflight ILS together with the relative widening of the wings of the ILS is insensitive to the sampling grid position and accurately captures the variation of ILS in the O2 A band between decontamination events. These temporal changes of ILS may explain the spurious signals observed in the solar-induced fluorescence retrieval in barren areas.
Tropospheric emissions: Monitoring of pollution (TEMPO)Zoogman, P.Liu, X.Suleiman, R. M.Pennington, W. F.Flittner, D. E.Al-Saadi, J. A.Hilton, B. B.Nicks, D. K.Newchurch, M. J.Carr, J. L. Janz, S. J.Andraschko, M. R.Arola, A.Baker, B. D.Canova, B. P.Chan Miller, C.Cohen, R. C.Davis, J. E.Dussault, M. E.Edwards, D. P.Fishman, J.Ghulam, A.González Abad, GonzaloGrutter, M.Herman, J. R.Houck, J.Jacob, D. J.Joiner, J.Kerridge, B. J.Kim, J.Krotkov, N. A.Lamsal, L.Li, C.Lindfors, A.Martin, R. V.McElroy, C. T.McLinden, C.Natraj, V.Neil, D. O.Nowlan, C. R.O'Sullivan, E. J.Palmer, P. I.Pierce, R. B.Pippin, M. R.Saiz-Lopez, A.Spurr, R. J. D.Szykman, J. J.Torres, O.Veefkind, J. P.Veihelmann, B.Wang, H.Wang, J.Chance, Kelly V.DOI: info:10.1016/j.jqsrt.2016.05.008v. 18617–39
Zoogman, P., Liu, X., Suleiman, R. M., Pennington, W. F., Flittner, D. E., Al-Saadi, J. A., Hilton, B. B., Nicks, D. K., Newchurch, M. J., Carr, J. L., Janz, S. J., Andraschko, M. R., Arola, A., Baker, B. D., Canova, B. P., Chan Miller, C., Cohen, R. C., Davis, J. E., Dussault, M. E., Edwards, D. P., Fishman, J., Ghulam, A., González Abad, Gonzalo, Grutter, M., Herman, J. R. et al. 2017. "Tropospheric emissions: Monitoring of pollution (TEMPO)." Journal of Quantitative Spectroscopy and Radiative Transfer 186:17– 39. https://doi.org/10.1016/j.jqsrt.2016.05.008
ID: 142310
Type: article
Authors: Zoogman, P.; Liu, X.; Suleiman, R. M.; Pennington, W. F.; Flittner, D. E.; Al-Saadi, J. A.; Hilton, B. B.; Nicks, D. K.; Newchurch, M. J.; Carr, J. L. ; Janz, S. J.; Andraschko, M. R.; Arola, A.; Baker, B. D.; Canova, B. P.; Chan Miller, C.; Cohen, R. C.; Davis, J. E.; Dussault, M. E.; Edwards, D. P.; Fishman, J.; Ghulam, A.; González Abad, Gonzalo; Grutter, M.; Herman, J. R.; Houck, J.; Jacob, D. J.; Joiner, J.; Kerridge, B. J.; Kim, J.; Krotkov, N. A.; Lamsal, L.; Li, C.; Lindfors, A.; Martin, R. V.; McElroy, C. T.; McLinden, C.; Natraj, V.; Neil, D. O.; Nowlan, C. R.; O'Sullivan, E. J.; Palmer, P. I.; Pierce, R. B.; Pippin, M. R.; Saiz-Lopez, A.; Spurr, R. J. D.; Szykman, J. J.; Torres, O.; Veefkind, J. P.; Veihelmann, B.; Wang, H.; Wang, J.; Chance, Kelly V.
Abstract: 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 ( 2.1 km N/S×4.4 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide), water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring together with the European Sentinel-4 (S4) and Korean Geostationary Environment Monitoring Spectrometer (GEMS) instruments.
Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: retrieval algorithm and measurements during DISCOVER-AQ Texas 2013Nowlan, C. R.Liu, X.Leitch, J. W.Chance, Kelly V.González Abad, GonzaloLiu, C.Zoogman, P.Cole, J.Delker, T.Good, W.Murcray, F.Ruppert, L.Soo, D.Follette-Cook, M. B.Janz, S. J.Kowalewski, M. G.Loughner, C. P.Pickering, K. E.Herman, J. R.Beaver, M. R.Long, R. W.Szykman, J. J.Judd, L. M.Kelley, P.Luke, W. T.Ren, X.Al-Saadi, J. A.DOI: info:10.5194/amtd-8-13099-2015v. 813099–13155
Nowlan, C. R., Liu, X., Leitch, J. W., Chance, Kelly V., González Abad, Gonzalo, Liu, C., Zoogman, P., Cole, J., Delker, T., Good, W., Murcray, F., Ruppert, L., Soo, D., Follette-Cook, M. B., Janz, S. J., Kowalewski, M. G., Loughner, C. P., Pickering, K. E., Herman, J. R., Beaver, M. R., Long, R. W., Szykman, J. J., Judd, L. M., Kelley, P., Luke, W. T. et al. 2015. "Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: retrieval algorithm and measurements during DISCOVER-AQ Texas 2013." Atmospheric Measurement Techniques Discussions 8:13099– 13155. https://doi.org/10.5194/amtd-8-13099-2015
ID: 138597
Type: article
Authors: Nowlan, C. R.; Liu, X.; Leitch, J. W.; Chance, Kelly V.; González Abad, Gonzalo; Liu, C.; Zoogman, P.; Cole, J.; Delker, T.; Good, W.; Murcray, F.; Ruppert, L.; Soo, D.; Follette-Cook, M. B.; Janz, S. J.; Kowalewski, M. G.; Loughner, C. P.; Pickering, K. E.; Herman, J. R.; Beaver, M. R.; Long, R. W.; Szykman, J. J.; Judd, L. M.; Kelley, P.; Luke, W. T.; Ren, X.; Al-Saadi, J. A.
Abstract: The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a testbed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA Falcon aircraft in its first intensive field measurement campaign during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Earth Venture Mission over Houston, Texas in September 2013. Measurements of backscattered solar radiation between 420-465 nm collected on four days during the campaign are used to determine slant column amounts of NO2 at 250 m × 250 m spatial resolution with a fitting precision of 2.2 × 1015 molecules cm-2. These slant columns are converted to tropospheric NO2 vertical columns using a radiative transfer model and trace gas profiles from the Community Multiscale Air Quality (CMAQ) model. Total column NO2 from GeoTASO is well correlated with ground-based Pandora observations (r = 0.90 on the most polluted and cloud-free day of measurements), with GeoTASO NO2 slightly higher for the most polluted observations. Surface NO2 mixing ratios inferred from GeoTASO using the CMAQ model show good correlation with NO2 measured in situ at the surface during the campaign (r = 0.91 for the most polluted day). NO2 slant columns from GeoTASO also agree well with preliminary retrievals from the GEO-CAPE Airborne Simulator (GCAS) which flew on the NASA King Air B200 (r = 0.84, slope = 0.94). Enhanced NO2 is resolvable over areas of traffic NOx emissions and near individual petrochemical facilities.
Application of OMI, SCIAMACHY, and GOME-2 satellite SO2 retrievals for detection of large emission sourcesFioletov, V. E.McLinden, C. A.Krotkov, N.Yang, K.Loyola, D. G.Valks, P.Theys, N.Van Roozendael, M.Nowlan, C. R.Chance, Kelly V.Liu, X.Lee, C.Martin, R. V.DOI: info:10.1002/jgrd.50826v. 11811399
Fioletov, V. E., McLinden, C. A., Krotkov, N., Yang, K., Loyola, D. G., Valks, P., Theys, N., Van Roozendael, M., Nowlan, C. R., Chance, Kelly V., Liu, X., Lee, C., and Martin, R. V. 2013. "Application of OMI, SCIAMACHY, and GOME-2 satellite SO2 retrievals for detection of large emission sources." Journal of Geophysical Research. D. Atmospheres 118:11399. https://doi.org/10.1002/jgrd.50826
ID: 117764
Type: article
Authors: Fioletov, V. E.; McLinden, C. A.; Krotkov, N.; Yang, K.; Loyola, D. G.; Valks, P.; Theys, N.; Van Roozendael, M.; Nowlan, C. R.; Chance, Kelly V.; Liu, X.; Lee, C.; Martin, R. V.
Abstract: of sulfur dioxide (SO2) from space-based spectrometers are in a relatively early stage of development. Factors such as interference between ozone and SO2 in the retrieval algorithms often lead to errors in the retrieved values. Measurements from the Ozone Monitoring Instrument (OMI), Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and Global Ozone Monitoring Experiment-2 (GOME-2) satellite sensors, averaged over a period of several years, were used to identify locations with elevated SO2 values and estimate their emission levels. About 30 such locations, detectable by all three sensors and linked to volcanic and anthropogenic sources, were found after applying low and high spatial frequency filtration designed to reduce noise and bias and to enhance weak signals to SO2 data from each instrument. Quantitatively, the mean amount of SO2 in the vicinity of the sources, estimated from the three instruments, is in general agreement. However, its better spatial resolution makes it possible for OMI to detect smaller sources and with additional detail as compared to the other two instruments. Over some regions of China, SCIAMACHY and GOME-2 data show mean SO2 values that are almost 1.5 times higher than those from OMI, but the suggested spatial filtration technique largely reconciles these differences.
Characterization and correction of Global Ozone Monitoring Experiment 2 ultraviolet measurements and application to ozone profile retrievalsCai, ZhaonanLiu, YiLiu, XiongChance, Kelly V.Nowlan, Caroline R.Lang, RuedigerMunro, RosemarySuleiman, RaidDOI: info:10.1029/2011JD017096v. 11707305
Cai, Zhaonan, Liu, Yi, Liu, Xiong, Chance, Kelly V., Nowlan, Caroline R., Lang, Ruediger, Munro, Rosemary, and Suleiman, Raid. 2012. "Characterization and correction of Global Ozone Monitoring Experiment 2 ultraviolet measurements and application to ozone profile retrievals." Journal of Geophysical Research. D. Atmospheres 117:07305. https://doi.org/10.1029/2011JD017096
ID: 111428
Type: article
Authors: Cai, Zhaonan; Liu, Yi; Liu, Xiong; Chance, Kelly V.; Nowlan, Caroline R.; Lang, Ruediger; Munro, Rosemary; Suleiman, Raid
Abstract: We present an assessment study of the Global Ozone Monitoring Experiment 2 (GOME-2) reflectance for the wavelength range 270-350 nm by comparing measurements with simulations calculated using the vector linearized discrete ordinate radiative transfer model (VLIDORT) and Microwave Limb Sounder (MLS) ozone profiles. The results indicate wavelength- and cross-track-position-dependent biases. GOME-2 reflectance is overestimated by 10% near 300 nm and by 15%-20% around 270 nm. Stokes fraction measurements made by onboard polarization measurement devices are also validated directly using the VLIDORT model. GOME-2 measurements agree well with the simulated Stokes fractions, with mean biases ranging from -1.0% to ~2.9% the absolute differences are less than 0.05. Cloudiness-dependent biases suggest the existence of uncorrected stray-light errors that vary seasonally and latitudinally. Temporal analysis indicates that reflectance degradation began at the beginning of the mission; the reflectance degrades by 15% around 290 nm and by 2.2% around 325 nm from 2007 through 2009. Degradation shows wavelength- and viewing-angle-dependent features. Preliminary validation of ozone profile retrievals with MLS, Michelson Interferometer for Passive Atmospheric Sounding, and ozonesonde reveals that the application of radiometric recalibration improves the ozone profile retrievals as well as reduces fitting residuals by 30% in band 2b.