Validity of the lifetime drinking history: A comparison of retrospective and prospective quantity-frequency measures

OBJECTIVE: The Lifetime Drinking History (LDH) has been used to examine alcohol use throughout the life span. Given its retrospective nature, it is important to examine the validity of the assessment. METHOD: Building on previous work establishing the reliability and validity of the LDH, the current study examined a sample of 1,295 men in the Vietnam Era Twin Registry. The men were assessed retrospectively with the LDH in 2000, at an average age of 51. The drinking patterns of these same men were also assessed prospectively in four prior studies, taking place in 1987, 1990, 1992, and 1995. RESULTS: Validity of the LDH was examined by comparing the correspondence between the prospective and retrospective quantity-frequency measures and reported age at first regular drinking. Correlations between the retrospective and prospective assessments were high for age at first regular drinking (.42-.58) and quantity-frequency measures (.47-.69), although some mean differences in the amount of consumption existed. CONCLUSIONS: Results support the use of the LDH in reporting phases of drinking across the life span

Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

We present an updated mechanism for tropospheric halogen (Cl&thinsp;+&thinsp;Br&thinsp;+&thinsp;I) chemistry in the GEOS-Chem global atmospheric chemical transport model and apply it to investigate halogen radical cycling and implications for tropospheric oxidants. Improved representation of HOBr heterogeneous chemistry and its pH dependence in our simulation leads to less efficient recycling and mobilization of bromine radicals and enables the model to include mechanistic sea salt aerosol debromination without generating excessive BrO. The resulting global mean tropospheric BrO mixing ratio is 0.19&thinsp;ppt (parts per trillion), lower than previous versions of GEOS-Chem. Model BrO shows variable consistency and biases in comparison to surface and aircraft observations in marine air, which are often near or below the detection limit. The model underestimates the daytime measurements of Cl2 and BrCl from the ATom aircraft campaign over the Pacific and Atlantic, which if correct would imply a very large missing primary source of chlorine radicals. Model IO is highest in the marine boundary layer and uniform in the free troposphere, with a global mean tropospheric mixing ratio of 0.08&thinsp;ppt, and shows consistency with surface and aircraft observations. The modeled global mean tropospheric concentration of Cl atoms is 630&thinsp;cm&minus;3, contributing 0.8&thinsp;% of the global oxidation of methane, 14&thinsp;% of ethane, 8&thinsp;% of propane, and 7&thinsp;% of higher alkanes. Halogen chemistry decreases the global tropospheric burden of ozone by 11&thinsp;%, NOx by 6&thinsp;%, and OH by 4&thinsp;%. Most of the ozone decrease is driven by iodine-catalyzed loss. The resulting GEOS-Chem ozone simulation is unbiased in the Southern Hemisphere but too low in the Northern Hemisphere. &nbsp; Full List of Authors: Xuan Wang1,2, Daniel J. Jacob3, William Downs3, Shuting Zhai4, Lei Zhu5, Viral Shah3, Christopher D. Holmes6, Tom&aacute;s Sherwen7,8, Becky Alexander4, Mathew J. Evans7,8, Sebastian D. Eastham9, J. Andrew Neuman10,11, Patrick R. Veres10, Theodore K. Koenig11,12, Rainer Volkamer11,12, L. Gregory Huey13, Thomas J. Bannan14, Carl J. Percival14,a, Ben H. Lee4, and Joel A. Thornton4 1School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China 2City University of Hong Kong Shenzhen Research Institute, Shenzhen, China 3School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA 4Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA 5School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, China 6Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, Florida, USA 7Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, UK 8National Centre for Atmospheric Science, University of York, York, UK 9Laboratory for Aviation and the Environment, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA 10NOAA Chemical Sciences Laboratory (CSL), Boulder, Colorado, USA 11Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA 12Department of Chemistry, University of Colorado, Boulder, Colorado, USA 13School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA 14School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK anow at: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA &nbsp;</p

Inter-comparison of MAX-DOAS measurements of tropospheric HONO slant column densities and vertical profiles during the CINDI-2 campaign

We present the inter-comparison of delta slant column densities (SCDs) and vertical profiles of nitrous acid (HONO) derived from measurements of different multi-axis differential optical absorption spectroscopy (MAX-DOAS) instruments and using different inversion algorithms during the Second Cabauw Inter-comparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) in September&nbsp;2016 at Cabauw, the Netherlands (51.97∘&thinsp;N, 4.93∘&thinsp;E). The HONO vertical profiles, vertical column densities (VCDs), and near-surface volume mixing ratios are compared between different MAX-DOAS instruments and profile inversion algorithms for the first time. Systematic and random discrepancies of the HONO results are derived from the comparisons of all data sets against their median values. Systematic discrepancies of HONO delta SCDs are observed in the range of &plusmn;0.3&times;1015&thinsp;molec.&thinsp;cm&minus;2, which is half of the typical random discrepancy of 0.6&times;1015&thinsp;molec.&thinsp;cm&minus;2. For a typical high HONO delta SCD of 2&times;1015&thinsp;molec.&thinsp;cm&minus;2, the relative systematic and random discrepancies are about 15&thinsp;% and 30&thinsp;%, respectively. The inter-comparison of HONO profiles shows that both systematic and random discrepancies of HONO VCDs and near-surface volume mixing ratios (VMRs) are mostly in the range of &sim;&plusmn;0.5&times;1014&thinsp;molec.&thinsp;cm&minus;2 and &sim;&plusmn;0.1&thinsp;ppb (typically &sim;20&thinsp;%). Further we find that the discrepancies of the retrieved HONO profiles are dominated by discrepancies of the HONO delta SCDs. The profile retrievals only contribute to the discrepancies of the HONO profiles by &sim;5&thinsp;%. However, some data sets with substantially larger discrepancies than the typical values indicate that inappropriate implementations of profile inversion algorithms and configurations of radiative transfer models in the profile retrievals can also be an important uncertainty source. In addition, estimations of measurement uncertainties of HONO dSCDs, which can significantly impact profile retrievals using the optimal estimation method, need to consider not only DOAS fit errors, but also atmospheric variability, especially for an instrument with a DOAS fit error lower than &sim;3&times;1014&thinsp;molec.&thinsp;cm&minus;2. The MAX-DOAS results during the CINDI-2 campaign indicate that the peak HONO levels (e.g. near-surface VMRs of &sim;0.4&thinsp;ppb) often appeared in the early morning and below 0.2&thinsp;km. The near-surface VMRs retrieved from the MAX-DOAS observations are compared with those measured using a co-located long-path DOAS instrument. The systematic differences are smaller than 0.15 and 0.07&thinsp;ppb during early morning and around noon, respectively. Since true HONO values at high altitudes are not known in the absence of real measurements, in order to evaluate the abilities of profile inversion algorithms to respond to different HONO profile shapes, we performed sensitivity studies using synthetic HONO delta SCDs simulated by a radiative transfer model with assumed HONO profiles. The tests indicate that the profile inversion algorithms based on the optimal estimation method with proper configurations can reproduce the different HONO profile shapes well. Therefore we conclude that the features of HONO accumulated near the surface derived from MAX-DOAS measurements are expected to represent the ambient HONO profiles well. Full List of Authors: Yang Wang1, Arnoud Apituley2, Alkiviadis Bais3, Steffen Beirle1, Nuria Benavent4, Alexander Borovski5, Ilya Bruchkouski6, Ka Lok Chan7,8, Sebastian Donner1, Theano Drosoglou3, Henning Finkenzeller9,10, Martina M. Friedrich11, Udo Frie&szlig;12, David Garcia-Nieto4, Laura G&oacute;mez-Mart&iacute;n13, Fran&ccedil;ois Hendrick11, Andreas Hilboll14, Junli Jin15, Paul Johnston16, Theodore K. Koenig9,10, Karin Kreher17, Vinod Kumar1, Aleksandra Kyuberis18, Johannes Lampel12,19, Cheng Liu20, Haoran Liu20, Jianzhong Ma21, Oleg L. Polyansky18,22, Oleg Postylyakov5, Richard Querel16, Alfonso Saiz-Lopez4, Stefan Schmitt12, Xin Tian23,24, Jan-Lukas Tirpitz12, Michel Van Roozendael11, Rainer Volkamer9,10, Zhuoru Wang8, Pinhua Xie24, Chengzhi Xing25, Jin Xu24, Margarita Yela13, Chengxin Zhang25, and Thomas Wagner11Max Planck Institute for Chemistry, Mainz, Germany 2Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands 3Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece 4Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano (CSIC), Madrid, Spain 5A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia 6National Ozone Monitoring Research and Education Center BSU (NOMREC BSU), Belarusian State University, Minsk, Belarus 7Meteorologisches Institut, Ludwig-Maximilians-Universit&auml;t M&uuml;nchen, Munich, Germany 8Remote Sensing Technology Institute, German Aerospace Center (DLR), Oberpfaffenhofen, Germany 9Department of Chemistry, University of Colorado Boulder, Boulder, CO, USA 10Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA 11Royal Belgian Institute for Space Aeronomy, Brussels, Belgium 12Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany 13National Institute of Aerospatial Technology, Madrid, Spain 14Institute of Environmental Physics, University of Bremen, Bremen, Germany 15Meteorological Observation Center, China Meteorological Administration, Beijing, China 16National Institute of Water &amp; Atmospheric Research (NIWA), Lauder, New Zealand 17BK Scientific, Mainz, Germany 18Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia 19Airyx GmbH, Justus-von-Liebig-Str. 14, 69214 Eppelheim, Germany 20Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, China 21Chinese Academy of Meteorology Science, China Meteorological Administration, Beijing, China 22Department of Physics and Astronomy, University College London, Gower St, London, WC1E 6BT, UK 23Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China 24Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China 25School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China </ul

The driving factors of new particle formation and growth in the polluted boundary layer

New particle formation (NPF) is a significant source of atmospheric particles, affecting climate and air quality. Understanding the mechanisms involved in urban aerosols is important to develop effective mitigation strategies. However, NPF rates reported in the polluted boundary layer span more than 4 orders of magnitude, and the reasons behind this variability are the subject of intense scientific debate. Multiple atmospheric vapours have been postulated to participate in NPF, including sulfuric acid, ammonia, amines and organics, but their relative roles remain unclear. We investigated NPF in the CLOUD chamber using mixtures of anthropogenic vapours that simulate polluted boundary layer conditions. We demonstrate that NPF in polluted environments is largely driven by the formation of sulfuric acid&ndash;base clusters, stabilized by the presence of amines, high ammonia concentrations and lower temperatures. Aromatic oxidation products, despite their extremely low volatility, play a minor role in NPF in the chosen urban environment but can be important for particle growth and hence for the survival of newly formed particles. Our measurements quantitatively account for NPF in highly diverse urban environments and explain its large observed variability. Such quantitative information obtained under controlled laboratory conditions will help the interpretation of future ambient observations of NPF rates in polluted atmospheres. Full List of Authors: Mao Xiao1, Christopher R. Hoyle1,2, Lubna Dada3, Dominik Stolzenburg4, Andreas K&uuml;rten5, Mingyi Wang6, Houssni Lamkaddam1, Olga Garmash3, Bernhard Mentler7, Ugo Molteni1, Andrea Baccarini1, Mario Simon5, Xu-Cheng He3, Katrianne Lehtipalo3,8, Lauri R. Ahonen3, Rima Baalbaki3, Paulus S. Bauer4, Lisa Beck3, David Bell1, Federico Bianchi3, Sophia Brilke4, Dexian Chen6, Randall Chiu9, Ant&oacute;nio Dias10, Jonathan Duplissy3,11, Henning Finkenzeller9, Hamish Gordon6, Victoria Hofbauer6, Changhyuk Kim13,14, Theodore K. Koenig9,a, Janne Lampilahti3, Chuan Ping Lee1, Zijun Li15, Huajun Mai13, Vladimir Makhmutov16, Hanna E. Manninen17, Ruby Marten1, Serge Mathot17, Roy L. Mauldin18,19, Wei Nie20, Antti Onnela17, Eva Partoll7, Tuukka Pet&auml;j&auml;3, Joschka Pfeifer5,17, Veronika Pospisilova1, Lauriane L. J. Qu&eacute;l&eacute;ver3, Matti Rissanen3,b, Siegfried Schobesberger15, Simone Schuchmann17,c, Yuri Stozhkov16, Christian Tauber4, Yee Jun Tham3, Ant&oacute;nio Tom&eacute;21, Miguel Vazquez-Pufleau4, Andrea C. Wagner5,9,d, Robert Wagner3, Yonghong Wang3, Lena Weitz5, Daniela Wimmer3,4, Yusheng Wu3, Chao Yan3, Penglin Ye6,22, Qing Ye6, Qiaozhi Zha3, Xueqin Zhou5, Antonio Amorim10, Ken Carslaw12, Joachim Curtius5, Armin Hansel7, Rainer Volkamer9,19, Paul M. Winkler4, Richard C. Flagan13, Markku Kulmala3,11,20,23, Douglas R. Worsnop3,22, Jasper Kirkby5,17, Neil M. Donahue6, Urs Baltensperger1, Imad El Haddad1, and Josef Dommen1 1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland 2Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland 3Institute for Atmospheric and Earth System Research (INAR)/Physics, University of Helsinki, 00014 Helsinki, Finland 4Faculty of Physics, University of Vienna, 1090 Vienna, Austria 5Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany 6Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA 7Institute of Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria 8Atmospheric Composition Research Unit, Finnish Meteorological Institute, 00560 Helsinki, Finland 9Department of Chemistry &amp; CIRES, University of Colorado Boulder, Boulder, CO 80309, USA 10CENTRA and FCUL, University of Lisbon, 1749-016 Lisbon, Portugal 11Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland 12School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom 13Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA 14School of Civil and Environmental Engineering, Pusan National University, 46241 Busan, Republic of Korea 15Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland 16Solar and Cosmic Ray Physics Laboratory, P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991 Moscow, Russian Federation 17CERN, 1211 Geneva, Switzerland 18Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA 19Department of Oceanic and Atmospheric Sciences, University of Colorado Boulder, Boulder, CO 80309, USA 20Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu Province, China 21IDL-Universidade da Beira Interior, Covilh&atilde;, Portugal 22Aerodyne Research Inc., Billerica, MA 01821-3976, USA 23Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China anow at: College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China bnow at: Aerosol Physics Laboratory, Physics Unit, Faculty of Engineering and Natural Sciences, Tampere University, 33720 Tampere, Finland cnow at: Experimentelle Teilchen- und Astroteilchenphysik, Johannes Gutenberg University Mainz, 55128 Mainz, Germany dnow at: Department of Chemistry &amp; CIRES, University of Colorado Boulder, Boulder, CO 80305, USA Correspondence: Urs Baltensperger ([email protected]) and Imad El Haddad ([email protected])</p

Knowledge, Attitudes, Practices and Beliefs about Medical Male Circumcision (MMC) among a Sample of Health Care Providers in Haiti

Background Haiti has the highest number of people living with HIV infection in the Caribbean/Latin America region. Medical male circumcision (MMC) has been recommended to help prevent the spread of HIV. We sought to assess knowledge, attitudes, practices and beliefs about MMC among a sample of health care providers in Haiti. Methods A convenience sample of 153 health care providers at the GHESKIO Centers in Haiti responded to an exploratory survey that collected information on several topics relevant to health providers about MMC. Descriptive statistics were calculated for the responses and multivariable logistic regression was conducted to determine opinions of health care providers about the best age to perform MMC on males. Bayesian network analysis and sensitivity analysis were done to identify the minimum level of change required to increase the acceptability of performing MMC at age less than 1 year. Results The sample consisted of medical doctors (31.0%), nurses (49.0%), and other health care professionals (20.0%). Approximately 76% showed willingness to offer MMC services if they received training. Seventy-six percent believed that their male patients would accept circumcision, and 59% believed infancy was the best age for MMC. More than 90% of participants said that MMC would reduce STIs. Physicians and nurses who were willing to offer MMC if provided with adequate training were 2.5 (1.15–5.71) times as likely to choose the best age to perform MMC as less than one year. Finally, if the joint probability of choosing “the best age to perform MMC” as one year or older and having the mistaken belief that MMC prevents HIV entirely is reduced by 63% then the probability of finding that performing MMC at less than one year acceptable to health care providers is increased by 35%. Conclusion Participants demonstrated high levels of knowledge and positive attitudes towards MMC. Although this study suggests that circumcision is acceptable among certain health providers in Haiti, studies with larger and more representative samples are needed to confirm this finding

Iodine chemistry in the chemistry-climate model SOCOL-AERv2-I

In this paper, we present a new version of the chemistry-climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3ĝ€¯%-4ĝ€¯% reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30ĝ€¯ppbv less ozone at low latitudes and up to 100ĝ€¯ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5ĝ€¯%-10ĝ€¯% depending on geographical location. In the lower troposphere, 75ĝ€¯% of the modeled ozone reduction originates from inorganic sources of iodine, 25ĝ€¯% from organic sources of iodine. At 50ĝ€¯hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5ĝ€¯%-2.5ĝ€¯%. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species.Fil: Karagodin Doyennel, Arseniy. The Institute for Atmospheric and Climate Science; Suiza. Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center; SuizaFil: Rozanov, Eugene. The Institute for Atmospheric and Climate Science; Suiza. Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center; Suiza. Saint Petersburg State University; RusiaFil: Sukhodolov, Timofei. Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center; Suiza. Saint Petersburg State University; Rusia. University of Natural Resources and Life Sciences; AustriaFil: Egorova, Tatiana. Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center; SuizaFil: Saiz López, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Cuevas, Carlos A.. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Fernandez, Rafael Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Interdisciplinario de Ciencias Básicas. - Universidad Nacional de Cuyo. Instituto Interdisciplinario de Ciencias Básicas; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Sherwen, Tomás. University of York; Reino UnidoFil: Volkamer, Rainer. The Institute for Atmospheric and Climate Science ; Suiza. State University of Colorado at Boulder; Estados Unidos. Cooperative Institute for Research in Environmental Sciences; Estados Unidos. Paul Scherrer Institute; SuizaFil: Koenig, Theodore K.. State University of Colorado at Boulder; Estados Unidos. Cooperative Institute for Research in Environmental Sciences; Estados UnidosFil: Giroud, Tanguy. The Institute for Atmospheric and Climate Science; SuizaFil: Peter, Thomas. The Institute for Atmospheric and Climate Science; Suiz

Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols

Terrestrial volcanism is known to emit mercury (Hg) into the atmosphere. However, despite many years of investigation, its net impact on the atmospheric Hg budget remains insufficiently constrained, in part because the transformations of Hg in volcanic plumes as they age and mix with background air are poorly understood. Here we report the observation of complete gaseous elemental mercury (GEM) depletion events in dilute and moderately aged (&amp; SIM;3-7 hours) volcanic plumes from Piton de la Fournaise on Reunion Island. While it has been suggested that co-emitted bromine could, once photochemically activated, deplete GEM in a volcanic plume, we measured low bromine concentrations in both the gas- and particle-phase and observed complete GEM depletion even before sunrise, ruling out a leading role of bromine chemistry here. Instead, we hypothesize that the GEM depletions were mainly caused by gas-particle interactions with sulfate-rich volcanic particles (mostly of submicron size), abundantly present in the dilute plume. We consider heterogeneous GEM oxidation and GEM uptake by particles as plausible manifestations of such a process and derive empirical rate constants. By extrapolation, we estimate that volcanic aerosols may scavenge 210 Mg y(-1) (67-480 Mg y(-1)) of Hg from the atmosphere globally, acting effectively as atmospheric mercury sink. While this estimate is subject to large uncertainties, it highlights that Hg transformations in aging volcanic plumes must be better understood to determine the net impact of volcanism on the atmospheric Hg budget and Hg deposition pathways

Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

The differential optical absorption spectroscopy (DOAS) method is a well-known remote sensing technique that is nowadays widely used for measurements of atmospheric trace gases, creating the need for harmonization and characterization efforts. In this study, an intercomparison exercise of DOAS retrieval codes from 17 international groups is presented, focusing on NO2 slant columns. The study is based on data collected by one instrument during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) in Mainz, Germany, in summer 2013. As data from the same instrument are used by all groups, the results are free of biases due to instrumental differences, which is in contrast to previous intercomparison exercises.While in general an excellent correlation of NO2 slant columns between groups of > 99.98% (noon reference fits) and > 99.2% (sequential reference fits) for all elevation angles is found, differences between individual retrievals are as large as 8% for NO2 slant columns and 100% for rms residuals in small elevation angles above the horizon.Comprehensive sensitivity studies revealed that absolute slant column differences result predominantly from the choice of the reference spectrum while relative differences originate from the numerical approach for solving the DOAS equation as well as the treatment of the slit function. Furthermore, differences in the implementation of the intensity offset correction were found to produce disagreements for measurements close to sunrise (8-10% for NO2, 80% for rms residual). The largest effect of [approximate] 8% difference in NO2 was found to arise from the reference treatment; in particular for fits using a sequential reference. In terms of rms fit residual, the reference treatment has only a minor impact. In contrast, the wavelength calibration as well as the intensity offset correction were found to have the largest impact (up to 80%) on rms residual while having only a minor impact on retrieved NO2 slant columns

Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

Smoke from wildfires is a significant source of air pollution, which can adversely impact air quality and ecosystems downwind. With the recently increasing intensity and severity of wildfires, the threat to air quality is expected to increase. Satellite-derived biomass burning emissions can fill in gaps in the absence of aircraft or ground-based measurement campaigns and can help improve the online calculation of biomass burning emissions as well as the biomass burning emissions inventories that feed air quality models. This study focuses on satellite-derived NOx emissions using the high-spatial-resolution TROPOspheric Monitoring Instrument (TROPOMI) NO2 dataset. Advancements and improvements to the satellite-based determination of forest fire NOx emissions are discussed, including information on plume height and effects of aerosol scattering and absorption on the satellite-retrieved vertical column densities. Two common top-down emission estimation methods, (1) an exponentially modified Gaussian (EMG) and (2) a flux method, are applied to synthetic data to determine the accuracy and the sensitivity to different parameters, including wind fields, satellite sampling, noise, lifetime, and plume spread. These tests show that emissions can be accurately estimated from single TROPOMI overpasses. The effect of smoke aerosols on TROPOMI NO2 columns (via air mass factors, AMFs) is estimated, and these satellite columns and emission estimates are compared to aircraft observations from four different aircraft campaigns measuring biomass burning plumes in 2018 and 2019 in North America. Our results indicate that applying an explicit aerosol correction to the TROPOMI NO2 columns improves the agreement with the aircraft observations (by about 10&thinsp;%&ndash;25&thinsp;%). The aircraft- and satellite-derived emissions are in good agreement within the uncertainties. Both top-down emissions methods work well; however, the EMG method seems to output more consistent results and has better agreement with the aircraft-derived emissions. Assuming a Gaussian plume shape for various biomass burning plumes, we estimate an average NOx e-folding time of 2&thinsp;&plusmn;1&thinsp;h from TROPOMI observations. Based on chemistry transport model simulations and aircraft observations, the net emissions of NOx are 1.3 to 1.5 times greater than the satellite-derived NO2 emissions. A correction factor of 1.3 to 1.5 should thus be used to infer net NOx emissions from the satellite retrievals of NO2. </div