Evaluation of modelled climatologies of O₃, CO, water vapour and NOy_{y} in the upper troposphere–lower stratosphere using regular in situ observations by passenger aircraft

Evaluating global chemistry models in the upper troposphere–lower stratosphere (UTLS) is an important step toward an improved understanding of the chemical composition in this region. This composition is regularly sampled through in situ measurements based on passenger aircraft, in the framework of the In-service Aircraft for a Global Observing System (IAGOS) research infrastructure. This study focuses on the comparison of the IAGOS measurements in ozone, carbon monoxide (CO), nitrogen reactive species (NOy) and water vapour, with a 25-year simulation output from the LMDZ-OR-INCA chemistry–climate model. For this purpose, we present and apply an extension of the Interpol-IAGOS software that projects the IAGOS data onto any model grid, in order to derive a gridded IAGOS product and a masked (sub-sampled) model product that are directly comparable to one another. Climatologies are calculated in the upper troposphere (UT) and in the lower stratosphere (LS) separately but also in the UTLS as a whole, as a demonstration for the models that do not sort out the physical variables necessary to distinguish between the UT and the LS. In the northern extratropics, the comparison in the UTLS layer suggests that the geographical distribution in the tropopause height is well reproduced by the model. In the separated layers, the model simulates well the water vapour climatologies in the UT and the ozone climatologies in the LS. There are opposite biases in CO in both UT and LS, which suggests that the cross-tropopause transport is overestimated. The NOy observations highlight the difficulty of the model in parameterizing the lightning emissions. In the tropics, the upper-tropospheric climatologies are remarkably well simulated for water vapour. They also show realistic CO peaks due to biomass burning in the most convective systems, and the ozone latitudinal variations are well correlated between the observations and the model. Ozone is more sensitive to lightning emissions than to biomass burning emissions, whereas the CO sensitivity to biomass burning emissions strongly depends on location and season. The present study demonstrates that the Interpol-IAGOS software is a tool facilitating the assessment of global model simulations in the UTLS, which is potentially useful for any modelling experiment involving chemistry climate or chemistry transport models

Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017

Megacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of the long range capabilities of the High Altitude and LOng Range Research Aircraft (HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe provide unique insight to test the current understanding of MPC pollution outflows. In order to obtain an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOPs) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles, and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning, the identification of pollution plumes, and the analysis of chemical transformations during transport. This paper describes the experimental deployment and scientific questions of the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area (Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven HALO research flights with an aircraft base in Germany for a total of 53 flight hours. An in-flight comparison of HALO with the collaborating UK-airborne platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the instrumentation on board. Overall, EMeRGe unites measurements of near- and far-field emissions and hence deals with complex air masses of local and distant sources. Regional transport of several European MPC outflows was successfully identified and measured. Chemical processing of the MPC emissions was inferred from airborne observations of primary and secondary pollutants and the ratios between species having different chemical lifetimes. Photochemical processing of aerosol and secondary formation or organic acids was evident during the transport of MPC plumes. Urban plumes mix efficiently with natural sources as mineral dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The present work provides an overview of the most salient results in the European context, with these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications.The HALO deployment during EMeRGe was funded by a consortium comprising the German Research Foundation (DFG) Priority Program HALO-SPP 1294, the Institute of Atmospheric Physics of DLR, the Max Planck Society (MPG), and the Helmholtz Association. Flora Kluge, Benjamin Schreiner, and Klaus Pfeilsticker acknowledge the support given by the DFG through the project nos. PF 384-16, PF 384-17, and PG 385-19. Ralf Koppmann and Marc Krebsbach acknowledge DFG funding through project no. KR3861_1-1. Katja Bigge acknowledges additional funding from the Heidelberg Graduate School for Physics. Johannes Schneider, Katharina Kaiser, and Stephan Borrmann acknowledge funding through the DFG (project no. 316589531). Lisa Eirenschmalz and Hans Schlager acknowledge support by DFG through project MEPOLL (SCHL1857/4-1). Anna B. Kalisz Hedegaard would like to thank DAAD and DLR for a Research Fellowship. Hans Schlager acknowledge financial support by the DLR TraK (Transport and Climate) project. Michael Sicard acknowledges support from the EU (GA nos. 654109, 778349, 871115, and 101008004) and the Spanish Government (ref. nos. CGL2017-90884-REDT, PID2019-103886RB-I00, RTI2018-096548-B-I00, and MDM-2016-0600). Midhun George, Yangzhuoran Liu, M. Dolores Andrés Hernández, and John Phillip Burrows acknowledge financial support from the University of Bremen. FLEXPART simulations were performed on the HPC cluster Aether at the University of Bremen, financed by DFG within the scope of the Excellence Initiative. Anne-Marlene Blechschmidt was partly funded through the CAMS-84 project. Jennifer Wolf acknowledges support from the German Federal Ministry for Economic Affairs and Energy – BMWi (project Digitally optimized Engineering for Services – DoEfS; contract no. 20X1701B). Theresa Harlass thanks DLR VOR for funding the young investigator research group “Greenhouse Gases”. Mariano Mertens, Patrick Jöckel, and Markus Kilian acknowledge resources of the Deutsches Klimarechenzentrum (DKRZ) granted by the WLA project ID bd0617 for the MECO(n) simulations and the financial support from the DLR projects TraK (Transport und Klima) and the Initiative and Networking Fund of the Helmholtz Association through the project “Advanced Earth System Modelling Capacity” (ESM). Bruna A. Holanda acknowledges the funding from Brazilian CNPq (process 200723/2015-4).Peer ReviewedArticle signat per 53 autors/es: M. Dolores Andrés Hernández (1), Andreas Hilboll (2), Helmut Ziereis (3), Eric Förster (4), Ovid O. Krüger (5), Katharina Kaiser (6,7), Johannes Schneider (7), Francesca Barnaba (8), Mihalis Vrekoussis (2,18), Jörg Schmidt (9), Heidi Huntrieser (3), Anne-Marlene Blechschmidt (1), Midhun George (1), Vladyslav Nenakhov (1,a), Theresa Harlass (3), Bruna A. Holanda (5), Jennifer Wolf (3), Lisa Eirenschmalz (3), Marc Krebsbach (10), Mira L. Pöhlker (5,b), Anna B. Kalisz Hedegaard (3,2), Linlu Mei (1), Klaus Pfeilsticker (11), Yangzhuoran Liu (1), Ralf Koppmann (10), Hans Schlager (3), Birger Bohn (12), Ulrich Schumann (3), Andreas Richter (1), Benjamin Schreiner (11), Daniel Sauer (3), Robert Baumann (3), Mariano Mertens (3), Patrick Jöckel (3), Markus Kilian (3), Greta Stratmann (3,c,) Christopher Pöhlker (5), Monica Campanelli (8), Marco Pandolfi (13), Michael Sicard (14,15), José L. Gómez-Amo (16), Manuel Pujadas (17), Katja Bigge (11), Flora Kluge (11), Anja Schwarz (9), Nikos Daskalakis (2), David Walter (5), Andreas Zahn (4), Ulrich Pöschl (5), Harald Bönisch (4), Stephan Borrmann (6,7), Ulrich Platt (11), and John P. Burrows (1) // (1) Institute of Environmental Physics, University of Bremen, Bremen, Germany; (2) Laboratory for Modeling and Observation of the Earth System, Institute of Environmental Physics, Bremen, Germany; (3) Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany; (4) Atmospheric Trace Gases and Remote Sensing, Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany; (5) Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany; (6) Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany, (7) Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany; (8) National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Rome, Italy; (9) Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany; (10) Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany; (11) Institute for Environmental Physics, University of Heidelberg, Heidelberg, Germany, (12) Institute of Energy and Climate Research IEK-8, Forschungszentrum Jülich, Jülich, Germany; (13) Consejo Superior de Investigaciones Científicas, Institute of Environmental Assessment and Water Research, Barcelona, Spain; (14) CommSensLab, Department of Signal Theory and Communications, Universitat Politècnica de Catalunya, Barcelona, Spain; (15) Ciències i Tecnologies de l’Espai-Centre de Recerca de l’Aeronàutica i de l’Espai/Institut d’Estudis Espacials de Catalunya), Universitat Politècnica de Catalunya, Barcelona, Spain; (16) Department of Earth Physics and Thermodynamics, University of Valencia, Burjassot, Spain; (17) Atmospheric Pollution Unit, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (Ciemat), Madrid, Spain; (18) Climate and Atmosphere Research Center (CARE-C), The Cyprus Institute, Nicosia, Cyprus anow at: Flight Experiments, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, GermanyPostprint (published version

Trapping, chemistry, and export of trace gases in the South Asian summer monsoon observed during CARIBIC flights in 2008

The CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) passenger aircraft observatory performed in situ measurements at 10–12 km altitude in the South Asian summer monsoon anticyclone between June and September 2008. These measurements enable us to investigate this atmospheric region (which so far has mostly been observed from satellites) using the broad suite of trace gases and aerosol particles measured by CARIBIC. Elevated levels of a variety of atmospheric pollutants (e.g. carbon monoxide, total reactive nitrogen oxides, aerosol particles, and several volatile organic compounds) were recorded. The measurements provide detailed information about the chemical composition of air in different parts of the monsoon anticyclone, particularly of ozone precursors. While covering a range of 3500 km inside the monsoon anticyclone, CARIBIC observations show remarkable consistency, i.e. with distinct latitudinal patterns of trace gases during the entire monsoon period. Using the CARIBIC trace gas and aerosol particle measurements in combination with the Lagrangian particle dispersion model FLEXPART, we investigated the characteristics of monsoon outflow and the chemical evolution of air masses during transport. The trajectory calculations indicate that these air masses originated mainly from South Asia and mainland Southeast Asia. Estimated photochemical ages of the air were found to agree well with transport times from a source region east of 90–95° E. The photochemical ages of the air in the southern part of the monsoon anticyclone were systematically younger (less than 7 days) and the air masses were mostly in an ozone-forming chemical mode. In its northern part the air masses were older (up to 13 days) and had unclear ozone formation or destruction potential. Based on analysis of forward trajectories, several receptor regions were identified. In addition to predominantly westward transport, we found evidence for efficient transport (within 10 days) to the Pacific and North America, particularly during June and September, and also of cross-tropopause exchange, which was strongest during June and July. Westward transport to Africa and further to the Mediterranean was the main pathway during July

Airborne observations of peroxy radicals during the EMeRGe campaign in Europe

In this study, airborne measurements of the sum of hydroperoxyl (HO$_2$) and organic peroxy (RO$_2$) radicals that react with nitrogen monoxide (NO) to produce nitrogen dioxide (NO$_2$), coupled with actinometry and other key trace gases measurements, have been used to test the current understanding of the fast photochemistry in the outflow of major population centres. The measurements were made during the airborne campaign of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) project in Europe on board the High Altitude and Long Range Research Aircraft (HALO). The measurements of RO$^∗_2$ on HALO were made using the in situ instrument Peroxy Radical Chemical Enhancement and Absorption Spectrometer (PeRCEAS). RO$^∗_2$ is to a good approximation the sum of peroxy radicals reacting with NO to produce NO$_2$. RO$^∗_2$ mixing ratios up to 120 pptv were observed in air masses of different origins and composition under different local actinometric conditions during seven HALO research flights in July 2017 over Europe. Radical production rates were estimated using knowledge of the photolysis frequencies and the RO$^∗_2$ precursor concentrations measured on board, as well as the relevant rate coefficients. Generally, high RO$^∗_2$ concentrations were measured in air masses with high production rates. In the air masses investigated, RO$^∗_2$ is primarily produced by the reaction of O$^1$D with water vapour and the photolysis of nitrous acid (HONO) and of the oxygenated volatile organic compounds (OVOCs, e.g. formaldehyde (HCHO) and glyoxal (CHOCHO)). Due to their short lifetime in most environments, the RO$^∗_2$ concentrations are expected to be in a photostationary steady state (PSS), i.e. a balance between production and loss rates is assumed. The RO$^∗_2$ production and loss rates and the suitability of PSS assumptions to estimate the RO$^∗_2$ mixing ratios and variability during the airborne observations are discussed. The PSS assumption for RO$^∗_2$ is considered robust enough to calculate RO$^∗_2$ mixing ratios for most conditions encountered in the air masses measured. The similarities and discrepancies between measured and PSS calculated RO$^∗_2$ mixing ratios are discussed. The dominant terminating processes for RO$^∗_2$ in the pollution plumes measured up to 2000 m are the formation of nitrous acid, nitric acid, and organic nitrates. Above2000 m, HO$_2$–HO$_2$ and HO$_2$–RO$_2$ reactions dominate the RO$^∗_2$ removal. RO$^∗_2$ calculations by the PSS analytical expression inside the pollution plumes probed often underestimated the measurements. The underestimation is attributed to the limitations of the PSS equation used for the analysis. In particular, this expression does not account for the yields of RO$^∗_2$ from the oxidation and photolysis of volatile organic compounds, VOCs, and OVOCs other than those measured during the EMeRGe research flights in Europe. In air masses with NO mixing ratios ≤ 50 pptv and low VOC/NO ratios, the RO$^∗_2$ measured is overestimated by the analytical expression. This may be caused by the formation of H$_2$O and O$_2$ from OH and HO$_2$, being about 4 times faster than the rate of the OH oxidation reaction of the dominant OVOCs considered

Mercury plumes in the global upper troposphere observed during flights with the CARIBIC observatory from May 2005 until June 2013

Tropospheric sections of flights with the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrumented Container) observatory from May 2005 until June 2013, are investigated for the occurrence of plumes with elevated Hg concentrations. Additional information on CO, CO, CH, NO, O, hydrocarbons, halocarbons, acetone and acetonitrile enable us to attribute the plumes to biomass burning, urban/industrial sources or a mixture of both. Altogether, 98 pollution plumes with elevated Hg concentrations and CO mixing ratios were encountered, and the Hg/CO emission ratios for 49 of them could be calculated. Most of the plumes were found overEast Asia, in the African equatorial region, over South America and over Pakistan and India. The plumes encountered over equatorial Africa and over South America originate predominantly from biomass burning, as evidenced by the low Hg/CO emission ratios andelevated mixing ratios of acetonitrile, CHCl and particle concentrations. The backward trajectories point to the regions around the Rift Valley and the Amazon Basin, with its outskirts, as the source areas. The plumes encountered over East Asia and over Pakistan and India are predominantly of urban/industrial origin, sometimes mixed with products of biomass/biofuel burning. Backward trajectories point mostly to source areas in China andnorthern India. The Hg/CO and Hg/CH emission ratios for several plumes are also presented and discussed

Proceedings of the 4th International Conference on Transport, Atmosphere and Climate

The "4th International Conference on Transport, Atmosphere and Climate (TAC-4)" held in Bad Kohlgrub (Germany), 2015, was organised with the objective of updating our knowledge on the impacts of transport on the composition of the atmosphere and on climate, three years after the TAC-3 conference in Prien am Chiemsee (Germany). The TAC-4 conference covered all aspects of the impact of the different modes of transport (aviation, road transport, shipping etc.) on atmospheric chemistry, microphysics, radiation and climate, in particular

Effects of transport on a biomass burning plume from Indochina during EMeRGe-Asia identified by WRF-Chem

The Indochina biomass burning (BB) season in springtime has a substantial environmental impact on the surrounding areas in Asia. In this study, we evaluated the environmental impact of a major long-range BB transport event on 19 March 2018 (a flight of the High Altitude and Long Range Research Aircraft (HALO; https://www.halo-spp.de, last access: 14 February 2023) research aircraft, flight F0319) preceded by a minor event on 17 March 2018 (flight F0317). Aircraft data obtained during the campaign in Asia of the Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales (EMeRGe) were available between 12 March and 7 April 2018. In F0319, results of 1 min mean carbon monoxide (CO), ozone (O$_3$), acetone (ACE), acetonitrile (ACN), organic aerosol (OA), and black carbon aerosol (BC) concentrations were up to 312.0, 79.0, 3.0, and 0.6 ppb and 6.4 and 2.5 µg m$^{−3}$, respectively, during the flight, which passed through the BB plume transport layer (BPTL) between the elevation of 2000–4000 m over the East China Sea (ECS). During F0319, the CO, O$_3$, ACE, ACN, OA, and BC maximum of the 1 min average concentrations were higher in the BPTL by 109.0, 8.0, 1.0, and 0.3 ppb and 3.0 and 1.3 µg m$^{−3}$ compared to flight F0317, respectively. Sulfate aerosol, rather than OA, showed the highest concentration at low altitudes (<1000 m) in both flights F0317 and F0319 resulting from the continental outflow in the ECS. The transport of BB aerosols from Indochina and its impacts on the downstream area were evaluated using a Weather Research Forecasting with Chemistry (WRF-Chem) model. The modeling results tended to overestimate the concentration of the species, with examples being CO (64 ppb), OA (0.3 µg m$^{−3}$), BC (0.2 µg m$^{−3}$), and O$_3$ (12.5 ppb) in the BPTL. Over the ECS, the simulated BB contribution demonstrated an increasing trend from the lowest values on 17 March 2018 to the highest values on 18 and 19 March 2018 for CO, fine particulate matter (PM$_{2.5}$), OA, BC, hydroxyl radicals (OH), nitrogen oxides (NO$_x$), total reactive nitrogen (NO$_y$), and O$_3$; by contrast, the variation of J(O$^1$D) decreased as the BB plume\u27s contribution increased over the ECS. In the lower boundary layer (<1000 m), the BB plume\u27s contribution to most species in the remote downstream areas was <20 %. However, at the BPTL, the contribution of the long-range transported BB plume was as high as 30 %–80 % for most of the species (NO$_y$, NO$_x$, PM$_{2.5}$, BC, OH, O$_3$, and CO) over southern China (SC), Taiwan, and the ECS. BB aerosols were identified as a potential source of cloud condensation nuclei, and the simulation results indicated that the transported BB plume had an effect on cloud water formation over SC and the ECS on 19 March 2018. The combination of BB aerosol enhancement with cloud water resulted in a reduction of incoming shortwave radiation at the surface in SC and the ECS by 5 %–7 % and 2 %–4 %, respectively, which potentially has significant regional climate implications