Anke Roiger

Processes influencing ozone levels in Alaskan forest fire plumes during long-range transport over the North Atlantic

[1] A case of long-range transport of a biomass burning plume from Alaska to Europe is analyzed using a Lagrangian approach. This plume was sampled several times in the free troposphere over North America, the North Atlantic and Europe by three different aircraft during the IGAC Lagrangian 2K4 experiment which was part of the ICARTT/ ITOP measurement intensive in summer 2004. Measurements in the plume showed enhanced values of CO, VOCs and NOy, mainly in form of PAN. Observed O-3 levels increased by 17 ppbv over 5 days. A photochemical trajectory model, CiTTyCAT, was used to examine processes responsible for the chemical evolution of the plume. The model was initialized with upwind data and compared with downwind measurements. The influence of high aerosol loading on photolysis rates in the plume was investigated using in situ aerosol measurements in the plume and lidar retrievals of optical depth as input into a photolysis code (Fast-J), run in the model. Significant impacts on photochemistry are found with a decrease of 18% in O-3 production and 24% in O-3 destruction over 5 days when including aerosols. The plume is found to be chemically active with large O-3 increases attributed primarily to PAN decomposition during descent of the plume toward Europe. The predicted O-3 changes are very dependent on temperature changes during transport and also on water vapor levels in the lower troposphere which can lead to O-3 destruction. Simulation of mixing/dilution was necessary to reproduce observed pollutant levels in the plume. Mixing was simulated using background concentrations from measurements in air masses in close proximity to the plume, and mixing timescales ( averaging 6.25 days) were derived from CO changes. Observed and simulated O-3/CO correlations in the plume were also compared in order to evaluate the photochemistry in the model. Observed slopes change from negative to positive over 5 days. This change, which can be attributed largely to photochemistry, is well reproduced by multiple model runs even if slope values are slightly underestimated suggesting a small underestimation in modeled photochemical O-3 production. The possible impact of this biomass burning plume on O-3 levels in the European boundary layer was also examined by running the model for a further 5 days and comparing with data collected at surface sites, such as Jungfraujoch, which showed small O-3 increases and elevated CO levels. The model predicts significant changes in O-3 over the entire 10 day period due to photochemistry but the signal is largely lost because of the effects of dilution. However, measurements in several other BB plumes over Europe show that O-3 impact of Alaskan fires can be potentially significant over Europe.

Arctic Air Pollution: New Insights from POLARCAT-IPY

Given the rapid nature of climate change occurring in the Arctic and the difficulty climate models have in quantitatively reproducing observed changes such as sea ice loss, it is important to improve understanding of the processes leading to climate change in this region, including the role of short-lived climate pollutants such as aerosols and ozone. It has long been known that pollution produced from emissions at midlatitudes can be transported to the Arctic, resulting in a winter/spring aerosol maximum known as Arctic haze. However, many uncertainties remain about the composition and origin of Arctic pollution throughout the troposphere; for example, many climate–chemistry models fail to reproduce the strong seasonality of aerosol abundance observed at Arctic surface sites, the origin and deposition mechanisms of black carbon (soot) particles that darken the snow and ice surface in the Arctic is poorly understood, and chemical processes controlling the abundance of tropospheric ozone are not well quant...

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

AbstractBetween 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...

Quantifying Emerging Local Anthropogenic Emissions in the Arctic Region: The ACCESS Aircraft Campaign Experiment

AbstractArctic sea ice has decreased dramatically in the past few decades and the Arctic is increasingly open to transit shipping and natural resource extraction. However, large knowledge gaps exist regarding composition and impacts of emissions associated with these activities. Arctic hydrocarbon extraction is currently under development owing to the large oil and gas reserves in the region. Transit shipping through the Arctic as an alternative to the traditional shipping routes is currently underway. These activities are expected to increase emissions of air pollutants and climate forcers (e.g., aerosols, ozone) in the Arctic troposphere significantly in the future. The authors present the first measurements of these activities off the coast of Norway taken in summer 2012 as part of the European Arctic Climate Change, Economy, and Society (ACCESS) project. The objectives include quantifying the impact that anthropogenic activities will have on regional air pollution and understanding the connections to ...

Chemical Composition of the Atmosphere

Atmospheric trace gases have an important impact on Earth’s radiative budget, the oxidative or cleansing ability of the atmosphere, the formation, growth and properties of aerosols, air quality, and human health. During recent years, the coupling between atmospheric chemistry and climate has received particular attention. Therefore, research is now focused on the composition and processes in the upper troposphere and lower stratosphere, a key region in this respect. In this chapter the chemical composition of the atmosphere is addressed and selected examples of significant advances in this field are presented.

Local Arctic air pollution: Sources and impacts

Local emissions of Arctic air pollutants and their impacts on climate, ecosystems and health are poorly understood. Future increases due to Arctic warming or economic drivers may put additional pressures on the fragile Arctic environment already affected by mid-latitude air pollution. Aircraft data were collected, for the first time, downwind of shipping and petroleum extraction facilities in the European Arctic. Data analysis reveals discrepancies compared to commonly used emission inventories, highlighting missing emissions (e.g. drilling rigs) and the intermittent nature of certain emissions (e.g. flaring, shipping). Present-day shipping/petroleum extraction emissions already appear to be impacting pollutant (ozone, aerosols) levels along the Norwegian coast and are estimated to cool and warm the Arctic climate, respectively. Future increases in shipping may lead to short-term (long-term) warming (cooling) due to reduced sulphur (CO2) emissions, and be detrimental to regional air quality (ozone). Further quantification of local Arctic emission impacts is needed.

Long-Range Transport of Air Pollutants

Air pollutants may be transported over several 1 000 km ranges, across continents, oceans (intercontinental), hemispheres, or even globally, depending on lifetime and other properties. Transported emissions include primary pollutants emitted from industry and vehicles (e.g., nitric oxide) and natural pollutants released by forest fires (e.g., soot). Also secondary pollutants (e.g., ozone) that are formed near the source region undergo transport. Recent advances in understanding atmospheric transport pathways, source-receptor relationships, and transformation of pollutants during transport are described.

Chemical Ionization Mass Spectrometric Measurements of Atmospheric Trace Gases

Chemical Ionization Mass Spectrometry (CIMS) is a versatile, fast and sensitive method for the detection of atmospheric trace gases, which play key roles in atmospheric chemistry and climate. A combination of different types of mass spectrometers, ion sources and inlet configurations are deployed by IPA. Sophisticated calibration techniques and in-flight calibration systems are developed to ensure high data quality. The CIMS instruments are employed preferably on research aircraft; in addition, observations are performed on ships, ground based sites and in laboratory scenarios including atmospheric chambers.