Evaluating modelled tropospheric columns of CH4_4 , CO, and O3_3 in the Arctic using ground-based Fourier transform infrared (FTIR) measurements

This study evaluates tropospheric columns of methane, carbon monoxide, and ozone in the Arctic simulated by 11 models. The Arctic is warming at nearly 4 times the global average rate, and with changing emissions in and near the region, it is important to understand Arctic atmospheric composition and how it is changing. Both measurements and modelling of air pollution in the Arctic are difficult, making model validation with local measurements valuable. Evaluations are performed using data from five high-latitude ground-based Fourier transform infrared (FTIR) spectrometers in the Network for the Detection of Atmospheric Composition Change (NDACC). The models were selected as part of the 2021 Arctic Monitoring and Assessment Programme (AMAP) report on short-lived climate forcers. This work augments the model–measurement comparisons presented in that report by including a new data source: column-integrated FTIR measurements, whose spatial and temporal footprint is more representative of the free troposphere than in situ and satellite measurements. Mixing ratios of trace gases are modelled at 3-hourly intervals by CESM, CMAM, DEHM, EMEP MSC-W, GEM- MACH, GEOS-Chem, MATCH, MATCH-SALSA, MRI-ESM2, UKESM1, and WRF-Chem for the years 2008, 2009, 2014, and 2015. The comparisons focus on the troposphere (0–7 km partial columns) at Eureka, Canada; Thule, Greenland; Ny Ålesund, Norway; Kiruna, Sweden; and Harestua, Norway. Overall, the models are biased low in the tropospheric column, on average by −9.7 % for CH$_4$, −21 % for CO, and −18 % for O$_3$. Results for CH$_4$ are relatively consistent across the 4 years, whereas CO has a maximum negative bias in the spring and minimum in the summer and O$_3$ has a maximum difference centered around the summer. The average differences for the models are within the FTIR uncertainties for approximately 15 % of the model–location comparisons

Overview : Integrative and Comprehensive Understanding on Polar Environments (iCUPE) - concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project "iCUPE - integrative and Comprehensive Understanding on Polar Environments" to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.Peer reviewe

Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results

The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context

Regional modeling of aerosols and ozone in the arctic : air quality and radiative impacts from local and remote pollution sources

La région arctique s’ouvre peu à peu aux activités humaines, en raison du réchauffement climatique et de la fonte des glaces, dûs en partie aux effets radiatifs des aérosols et de l'ozone. En conséquence, les émissions locales de pollution en Arctique pourraient augmenter, et devenir prépondérantes comparées à la source historique liée au transport de pollution depuis les moyennes latitudes. Dans cette thèse, j’effectue des simulations régionales de la troposphère arctique avec le modèle WRF-Chem, combiné à de nouveaux inventaires des émissions de pollution locales en Arctique (navigation et torches pétrolières). Deux cas d’étude issus de campagnes de mesure par avion sont analysés. Premièrement, j’étudie un évènement de transport d’aérosols depuis l’Europe au printemps 2008, afin d’améliorer les connaissances sur cette source majeure de pollution. Deuxièmement, je détermine l’impact des émissions de la navigation en Norvège en été 2012, où la navigation Arctique est actuellement la plus intense. J’utilise ces cas d’étude pour valider la pollution modélisée et améliorer WRF-Chem en Arctique. J’effectue avec ce modèle amélioré des simulations des impacts actuels (2012) et futurs (2050) de la navigation et des torches pétrolières en Arctique. Les résultats indiquent que les torches sont et devraient rester une source majeure d’aérosols de carbone suie réchauffant en Arctique. La navigation en Arctique est une source de pollution importante en été et, en 2050, pourrait devenir une source majeure de pollution locale.The Arctic is increasingly open to human activity due to rapid warming, associated with decreased sea ice extent. This warming is due, in part, to the effect of short-lived atmospheric pollutants (aerosols, ozone). As a result, Arctic pollutant emissions should increase in the future, and their impacts might become significant compared to the now predominant source due to pollution transport from the mid-latitudes. In this thesis, regional simulations of the Arctic troposphere are performed with the WRF-Chem model, combined with new emission estimates for oil and gas extraction and shipping in the Arctic. The model is used to analyze two case studies from recent airborne measurement datasets: POLARCAT-France in 2008, ACCESS in 2012. First, I investigate an aerosol transport event from Europe to the Arctic in spring 2008, in order to improve our understanding of this major source of Arctic pollution. Second, I determine the air quality and radiative impacts of shipping emissions in Northern Norway in summer 2012, where most current Arctic shipping occurs. I use these results to validate modeled pollution, and to improve WRF-Chem for Arctic studies. The updated model is used to investigate the current (2012) and future (2050) impacts of Arctic shipping and Arctic gas flaring in terms of air quality and radiative effects. Results show that Arctic flaring emissions are and should remain a strong source of local black carbon aerosols, causing warming, and that Arctic shipping is already a strong source of aerosols and ozone during summer. In 2050, diversion shipping through the Arctic Ocean could become a major source of local surface aerosol and ozone pollution

Modélisation régionale des polluants à courte durée de vie (aérosols, ozone) en Arctique

The Arctic is increasingly open to human activity due to rapid warming, associated with decreased sea ice extent. This warming is due, in part, to the effect of short-lived atmospheric pollutants (aerosols, ozone). As a result, Arctic pollutant emissions should increase in the future, and their impacts might become significant compared to the now predominant source due to pollution transport from the mid-latitudes. In this thesis, regional simulations of the Arctic troposphere are performed with the WRF-Chem model, combined with new emission estimates for oil and gas extraction and shipping in the Arctic. The model is used to analyze two case studies from recent airborne measurement datasets: POLARCAT-France in 2008, ACCESS in 2012. First, I investigate an aerosol transport event from Europe to the Arctic in spring 2008, in order to improve our understanding of this major source of Arctic pollution. Second, I determine the air quality and radiative impacts of shipping emissions in Northern Norway in summer 2012, where most current Arctic shipping occurs. I use these results to validate modeled pollution, and to improve WRF-Chem for Arctic studies. The updated model is used to investigate the current (2012) and future (2050) impacts of Arctic shipping and Arctic gas flaring in terms of air quality and radiative effects. Results show that Arctic flaring emissions are and should remain a strong source of local black carbon aerosols, causing warming, and that Arctic shipping is already a strong source of aerosols and ozone during summer. In 2050, diversion shipping through the Arctic Ocean could become a major source of local surface aerosol and ozone pollution.La région arctique s’ouvre peu à peu aux activités humaines, en raison du réchauffement climatique et de la fonte des glaces, dûs en partie aux effets radiatifs des aérosols et de l'ozone. En conséquence, les émissions locales de pollution en Arctique pourraient augmenter, et devenir prépondérantes comparées à la source historique liée au transport de pollution depuis les moyennes latitudes. Dans cette thèse, j’effectue des simulations régionales de la troposphère arctique avec le modèle WRF-Chem, combiné à de nouveaux inventaires des émissions de pollution locales en Arctique (navigation et torches pétrolières). Deux cas d’étude issus de campagnes de mesure par avion sont analysés. Premièrement, j’étudie un évènement de transport d’aérosols depuis l’Europe au printemps 2008, afin d’améliorer les connaissances sur cette source majeure de pollution. Deuxièmement, je détermine l’impact des émissions de la navigation en Norvège en été 2012, où la navigation Arctique est actuellement la plus intense. J’utilise ces cas d’étude pour valider la pollution modélisée et améliorer WRF-Chem en Arctique. J’effectue avec ce modèle amélioré des simulations des impacts actuels (2012) et futurs (2050) de la navigation et des torches pétrolières en Arctique. Les résultats indiquent que les torches sont et devraient rester une source majeure d’aérosols de carbone suie réchauffant en Arctique. La navigation en Arctique est une source de pollution importante en été et, en 2050, pourrait devenir une source majeure de pollution locale

Seeking the origins of Arctic ice nucleating particles with FLEXPART-WRF

International audienceThe Arctic region is subject to polar amplification, causing it to warm approximately four times faster than the global average. The predominance of ice and mixed-phase clouds in high latitude regions causes strong uncertainties in the determination of the cloud radiative effect and the cloud feedback. The representation of these clouds in models is therefore a crucial point for climate prediction. Solid and liquid water phases partitioning in mixed-phase clouds is mostly driven by their formation and growth processes, in which aerosol particles play a major role, especially in the Arctic where those particles are scarce. Although ice nucleating particles (INPs) may have relevant impact on weather and climate, their physical and chemical properties stay poorly understood. One of the main reasons is the lack of knowledge about their nature; the latter being mainly determined by their sources and thereby their geographical origins.In this study, in situ measurements from several recent data-sets are used to determine the likely origins of warm Arctic INPs (activated between -10°C and -20°C). A statistical method is applied on the backtrajectories derived from the lagrangian dispersion model FLEXPART-WRF, allows to characterize the seasonal variability of the identified INPs’ sources encountered over the arctic basin.The seasonal analysis shows that contributions of continental and marine sources to INPs concentrations are highly time- and space-dependent. Arctic INPs do not come exclusively from local sources and can originate from long-range transport. However, the general strong contribution of sea ice and open ocean regions to high concentrations of INPs, and its seasonal variability, is a clue about the importance of local sources. It emphasizes the hypothesis that marine biologic sources are among the main contributors to INPs emissions in the Arctic, when air masses coming from continental regions are often weak contributors. Also, the discrete strong contribution of sea ice regions, particularly in Autumn, suggests that mechanisms like blowing snow or emission of sea sprays from leads and marginal sea ice could have a relevant impact on Arctic INPs production.These results show the potential of this approach to characterize the origins of in situ measured species, and call for the method to be used in future studies on aerosols emissions

Comparing the effect of remote emissions and emerging local sources of Arctic pollution on Arctic aerosols and ozone and their impacts

International audienceAerosol and ozone pollution in the Arctic predominantly originates from long-range pollution transport of anthropogenic and biomass burning emissions from the midlatitudes. However, local emission sources such as shipping and oil and gas extraction could already have an important local or regional influence on atmospheric composition and on the Arctic energy budget, even though this influence is not well characterized. In this work, we perform quasi-hemispheric simulations of aerosols and ozone in the Arctic with the WRF-Chem model. The model is used to evaluate and compare the impacts of midlatitude anthropogenic emissions, biomass burning, and local Arctic emissions (oil and gas, shipping) in terms of atmospheric composition, cloud/aerosol interactions, pollutant deposition and radiative forcing in the Arctic. Local Arctic emissions are expected to increase in the future due to Arctic warming and reduced sea ice cover. For this reason we also compare the impact of these different sources in 2050, for a future scenario with high Arctic shipping growth and decreasing midlatitude anthropogenic emissions

Evaluating cloud-aerosol interaction parameterizations in the WRF-Chem model against cloud observations during a large volcanic eruption

International audienceIn 2014/2015, the intense eruption of the Holuhraun/Bárðarbunga volcano in Iceland emitted extreme amounts of SO2, far above the anthropogenic or natural background. This event had major impacts on cloud properties observed by satellite in the Northern Atlantic. Malavelle et al. (2017) showed that many climate models struggled to reproduce these observed impacts on clouds, indicating potential serious issues in the cloud-aerosol interaction frameworks currently used in models. These issues could explain part of the very large uncertainty remaining in current estimates of the radiative effect of aerosol-cloud interactions.Here, we use MODIS observations of cloud properties during the eruption to evaluate 3 different cloud-aerosol interaction approaches of decreasing complexity in the WRF-Chem 4 regional atmospheric model: First, the default model setup, using the Abdul-Razzak and Ghan (2000) parameterization (AR2000), coupling MOSAIC-4bin aerosols to the Morrison-2-moment microphysics. Second, the Thompson & Eidhammer (2014) aerosol-aware microphysics (TE2014), coupled for this study to MOSAIC-4bin aerosols. Third, the default version of TE2014 in WRF 4 using forced offline aerosols, where we replaced the original static aerosol climatology with 3D time-varying aerosols during the eruption. This last simplified approach does not require simulating fully interactive aerosols, and could be used to investigate regional cloud-aerosol processes and radiative forcing at high resolutions and climate time scales at a lower computational cost.In addition, we compare how these 3 cloud-aerosol approaches impact the detailed cloud response during the eruption in terms of cloud microphysical and optical properties, radiative fluxes, and precipitation

Aerosol background concentrations influence aerosol-cloud interactions as much as the choice of aerosol-cloud parameterization

Soumis a Geophysical Research LettersWe use an independent observational estimate of aerosol-cloud interactions (ACI) during the 2014 Holuhraun volcanic eruption in Iceland to evaluate 4 ACI parameterizations in a regional model. All parameterizations reproduce the observed pattern of liquid cloud droplet size reduction during the eruption, but strongly differ on its magnitude and on the resulting effective radiative forcing (ERF). Our results contradict earlier findings that this eruption could be used to constrain liquid water path (LWP) adjustments in models, except to exclude extremely high LWP adjustments of more than 20 g/m2. The modeled ERF is very sensitive to the non-volcanic background aerosol concentration: doubling the non-volcanic aerosol background weakens the ACI ERF by ˜30%. Since aerosol biases in climate models can be an order of magnitude or more, these results suggest that aerosol background concentrations could be a major and under-examined source of uncertainty for modeling ACI. Hosted</div

Heterogeneous ice nucleation in the WRF-Chem 3.9.1.1 model and its influence on cloudresponse to volcanic aerosols

International audienceHeterogeneous ice formation on aerosols is the main primary cloud ice formation process above temperatures of -38°C, and asa consequence it plays a major role in the formation of mixed-phase and ice clouds. Improving our understanding of iceprocesses could help better constrain the radiative forcing of cloud aerosol interactions, which remains a major source ofuncertainty in climate projections. Despite their importance, most atmospheric models do not represent aerosol-cloud iceprocesses explicitly.We extend in the WRF-Chem 3.9.1 model a recent parameterization of deposition-mode ice nucleation to also includeimmersion-mode nucleation, based on the classical nucleation theory (CNT) description. We also couple this parameterizationwith the aerosol-liquid cloud parameterization of Abdul Razzak and Ghan already included in WRF-Chem 3.9.1. This allows us tomodel the effect of aerosols on mixed-phase and ice clouds. We use volcanic eruptions as case studies, especially focusing onthe 2014/2015 Holuhraun/Bárðarbunga eruption in Iceland. Specifically, we investigate how volcanic aerosols influencemodeled cloud microphysical properties with and without the explicit ice nucleation parameterization, comparing the modelagainst MODIS satellite observations. We also investigate the effect of these processes on the cloud response in terms ofoptical properties, radiative fluxes, and precipitation during the eruption