Investigation of Inorganic Stratospheric Bromine using Balloon-Borne DOAS Measurements and Model Simulations

Inorganic bromine is the second most important halogen effecting stratospheric ozone [WMO2003]. Although the concentration of bromine in the stratosphere is about two orders of magnitude lower than the concentration of chlorine, it currently contributes about 25% to global ozone loss due to its much greater ozone depletion efficiency (factor of around 45) compared to chlorine. In this study, stratospheric balloon-borne DOAS (Differential Optical Absorption Spectroscopy) measurements of bromine-monoxide (BrO) were analysed and interpreted using the 3-D CTM (Chemical Transport Model) SLIMCAT [Chipperfield98] and a 1-D photochemical model. Photochemical changes were calculated along air mass trajectories which match the balloon data with SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) satellite observations in order to produce a set of BrO profiles suitable for SCIAMACHY validation. Furthermore, DOAS BrO observations were used to infer the trend of total inorganic stratospheric bromine, which peaked around 1998 at (21+-3) pptv and is consistently 3.5 to 5 pptv higher than the known trend in organic bromine precursors (halons and methyl bromide) can account for. This discrepancy, the non-zero amount of inorganic bromine observed around the tropopause and the rapid increase above the tropopause, all indicate that short-lived organic bromine source gases have to be taken into account. These results were confirmed by comparing the DOAS BrO data with different SLIMCAT model runs. Moreover, previous discrepancies between DOAS OClO measurements and model comparisons [Fitzenberger00b] were removed and detailed model studies were used to investigate ozone loss on specific days and the consistency of the known stratospheric photochemistry

Numerical simulation of the impact of COVID-19 lockdown on tropospheric composition and aerosol radiative forcing in Europe

Aerosols influence the Earth\u27s energy balance directly by modifying the radiation transfer and indirectly by altering the cloud microphysics. Anthropogenic aerosol emissions dropped considerably when the global COVID-19 pandemic resulted in severe restraints on mobility, production, and public life in spring 2020. We assess the effects of these reduced emissions on direct and indirect aerosol radiative forcing over Europe, excluding contributions from contrails. We simulate the atmospheric composition with the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model in a baseline (business-as-usual) and a reduced emission scenario. The model results are compared to aircraft observations from the BLUESKY aircraft campaign performed in May–June 2020 over Europe. The model agrees well with most of the observations, except for sulfur dioxide, particulate sulfate, and nitrate in the upper troposphere, likely due to a biased representation of stratospheric aerosol chemistry and missing information about volcanic eruptions. The comparison with a baseline scenario shows that the largest relative differences for tracers and aerosols are found in the upper troposphere, around the aircraft cruise altitude, due to the reduced aircraft emissions, while the largest absolute changes are present at the surface. We also find an increase in all-sky shortwave radiation of 0.21 ± 0.05 W m⁻² at the surface in Europe for May 2020, solely attributable to the direct aerosol effect, which is dominated by decreased aerosol scattering of sunlight, followed by reduced aerosol absorption caused by lower concentrations of inorganic and black carbon aerosols in the troposphere. A further increase in shortwave radiation from aerosol indirect effects was found to be much smaller than its variability. Impacts on ice crystal concentrations, cloud droplet number concentrations, and effective crystal radii are found to be negligible

Impact of reduced emissions on direct and indirect aerosol radiative forcing during COVID-19 lockdown in Europe

Aerosols influence the Earth’s energy balance through direct radiative effects and indirectly by altering the cloud microphysics. Anthropogenic aerosol emissions dropped considerably when the global COVID–19 pandemic resulted in severe restraints on mobility, production, and public life in spring 2020. Here we assess the effects of these reduced emissions on direct and indirect aerosol radiative forcing over Europe, excluding contributions from contrails. We simulate the atmospheric composition with the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model in a baseline (business as usual) and a reduced emission scenario. The model results are compared to aircraft observations from the BLUESKY aircraft campaign performed in May June 2020 over Europe

urbanLab Magazin - Fachzeitschrift für Stadt- & Quartiersplanung

Seit 2016 erscheint das urbanLab Magazin jährlich als Fachzeitschrift für Stadt- und Quartiersplanung mit dem Anspruch Forschung, Lehre und der Praxis in den Planungsdisziplinen des Spannungsfeldes Stadt und Quartier anhand konkreter Themencluster besser zu vernetzen. Wir geben zukunftsweisenden Ideen, Fachbeiträgen, Publikationen und kontroversen Diskussionen eine Plattform und bringen sie unterstützt durch Erkenntnisse aus unserer Forschung auf den Punkt

urbanLab Magazin - Fachzeitschrift für Stadt- & Quartiersplanung

Seit 2016 erscheint das urbanLab Magazin jährlich als Fachzeitschrift für Stadt- und Regionalplanung mit dem Anspruch Forschung, Lehre und der Praxis in den Planungsdisziplinen des Spannungsfeldes Stadt und Quartier anhand konkreter Themencluster besser zu vernetzen. Wir geben zukunftsweisenden Ideen, Fachbeiträgen, Publikationen und kontroversen Diskussionen eine Plattform und bringen sie unterstützt durch Erkenntnisse aus unserer Forschung auf den Punkt

Regional air pollution over Malaysia

International audienceDuring the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) campaign in Nov. and Dec. 2011 a number of polluted air masses were observed in the marine and terrestrial boundary layer (0 – 2 km) and in the free troposphere (2 – 12 km) over Borneo/Malaysia. The measurements include isoprene, CO, CO2, CH4, N2O, NO2, SO2 as primary pollutants, O3 and HCHO as secondary pollutants, and meteorological parameters. This set of trace gases can be used to fingerprint different sources of local and regional air pollution (e.g., biomass burning and fossil fuel burning, gas flaring on oil rigs, emission of ships and from urban areas, volcanic emissions, and biogenic emissions). Individual sources and location can be identified when the measurements are combined with a nested-grid regional scale chemical and meteorological model and lagrangian particle dispersion model (e.g., CCATT-BRAMS and FLEXPART). In the case of the former, emission inventories of the primary pollutants provide the basis for the trace gas simulations. In this region, the anthropogenic influence on air pollution seems to dominate over natural causes. For example, CO2 and CH4 often show strong correlations with CO, suggesting biomass burning or urban fossil fuel combustion dominates the combustion sources. The study of the CO/CO2 and CH4/CO ratios can help separate anthropogenic combustion from biomass burning pollution sources. In addition, these ratios can be used as a measure of combustion efficiency to help place the type of biomass burning particular to this region within the wider context of fire types found globally. On several occasions, CH4 enhancements are observed near the ocean surface, which are not directly correlated with CO enhancements thus indicating a non-combustion-related CH4 source. Positive correlations between SO2 and CO show the anthropogenic influence of oil rigs located in the South China Sea. Furthermore, SO2 enhancements are observed without any increase in CO, indicating possible volcanic emissions from the Indonesian islands to the South and East and the Philippines to the North East. The regional pollution seems to be influenced by emissions from Singapore, Philippines, Indonesia and Peninsula Malaysia, and on occasion by anthropogenic emissions from Thailand, Vietnam, Australia, and China

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

International audienceThe major volcanic eruption of Mount Pinatubo in 1991 has been shown to have significant effects on stratospheric chemistry and ozone depletion even at mid-latitudes. Since then, only "moderate" but recurrent volcanic eruptions have modulated the stratospheric aerosol loading such as the eruption of the mid-latitude Sarychev volcano which injected 0.9 Tg of sulfur dioxide (about 20 times less than Pinatubo) in June 2009. In this study, we investigate the chemical impacts of the enhanced liquid sulfate aerosol loading resulting from this moderate eruption using data from a balloon campaign conducted in northern Sweden (Kiruna-Esrange, 67.5° N, 21.0° E) in August-September 2009. Balloon-borne observations of NO2, HNO3 and BrO from infrared and UV-visible spectrometers are compared with the outputs of a three-dimensional (3-D) Chemistry-Transport Model (CTM). It is shown that differences between observations and model outputs are not due to transport calculation issues but rather reflect the chemical impact of the volcanic plume below 19 km in altitude. Good measurement-model agreement is obtained when the CTM is driven by volcanic aerosol loadings derived from in situ or space-borne data. As a result of enhanced N2O5 hydrolysis in the Sarychev volcanic aerosol conditions, the model calculates reductions of ~ 45 % and increases of ~ 11 % in NO2 and HNO3 amounts respectively over the summer 2009 period. The decrease in NOx abundances is limited due to the expected saturation effect for high aerosol loadings. The links between the various chemical catalytic cycles involving chlorine, bromine, nitrogen and HOx compounds in the lower stratosphere are discussed. The increased BrO amounts (~ 22 %) compare rather well with the balloon-borne observations when volcanic aerosol levels are accounted for in the CTM and appear to be mainly controlled by the coupling with nitrogen chemistry rather than by enhanced BrONO2 hydrolysis. Simulated effects of the Sarychev eruption on chlorine activation and partitioning are very limited in the high temperature conditions in the stratosphere at the period considered, inhibiting the effect of ClONO2 hydrolysis. As a consequence, the simulated ozone loss due to the Sarychev aerosols is low with a reduction of 1.1 % of the ozone budget at 16.5 km. Some comparisons with the reported Pinatubo chemical impacts are also provided and overall the Sarychev aerosols have led to less chemical effects than the Pinatubo event

ACRIDICON–CHUVA Campaign: Studying Tropical Deep Convective Clouds and Precipitation over Amazonia Using the New German Research Aircraft HALO

Between 1 September and 4 October 2014, a combined airborne and ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new German research aircraft, High Altitude and Long Range Research Aircraft (HALO), a modified Gulfstream G550, and extensive ground-based instrumentation were deployed in and near Manaus (State of Amazonas). The campaign was part of the German–Brazilian Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON– CHUVA) venture to quantify aerosol–cloud–precipitation interactions and their thermodynamic, dynamic, and radiative effects by in situ and remote sensing measurements over Amazonia. The ACRIDICON–CHUVA field observations were carried out in cooperation with the second intensive operating period of Green Ocean Amazon 2014/15 (GoAmazon2014/5). In this paper we focus on the airborne data measured on HALO, which was equipped with about 30 in situ and remote sensing instruments for meteorological, trace gas, aerosol, cloud, precipitation, and spectral solar radiation measurements

Evaluating global emission inventories of biogenic bromocarbons

Emissions of halogenated very short-lived substances (VSLS) are poorly constrained. However, their inclusion in global models is required to simulate a realistic inorganic bromine (Bry) loading in both the troposphere, where bromine chemistry perturbs global oxidizing capacity, and in the stratosphere, where it is a major sink for ozone (O3). We have performed simulations using a 3-D chemical transport model (CTM) including three top-down and a single bottom-up derived emission inventory of the major brominated VSLS bromoform (CHBr3) and dibromomethane (CH2Br2). We perform the first concerted evaluation of these inventories, comparing both the magnitude and spatial distribution of emissions. For a quantitative evaluation of each inventory, model output is compared with independent long-term observations at National Oceanic and Atmospheric Administration (NOAA) ground-based stations and with aircraft observations made during the NSF HIAPER Pole-to-Pole Observations (HIPPO) project. For CHBr3, the mean absolute deviation between model and surface observation ranges from 0.22 (38%) to 0.78 (115%) parts per trillion (ppt) in the tropics, depending on emission inventory. For CH2Br2, the range is 0.17 (24%) to 1.25 (167%) ppt. We also use aircraft observations made during the 2011 "Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere" (SHIVA) campaign, in the tropical West Pacific. Here, the performance of the various inventories also varies significantly, but overall the CTM is able to reproduce observed CHBr3 well in the free troposphere using an inventory based on observed sea-to-air fluxes. Finally, we identify the range of uncertainty associated with these VSLS emission inventories on stratospheric bromine loading due to VSLS (BryVSLS). Our simulations show BryVSLS ranges from ~ 4.0 to 8.0 ppt depending on the inventory. We report an optimised estimate at the lower end of this range (~ 4 ppt) based on combining the CHBr3 and CH2Br2 inventories which give best agreement with the compilation of observations in the tropics