Jan Eiof Jonson

Model calculations of present and future levels of ozone and ozone precursors with a global and a regional model

Abstract Levels of key chemical pollutants in the atmosphere are calculated for present (1996) and future (2010) emission scenarios with the help of a global model (Oslo CTM2), and a regional model (EMEP Eulerian Photochemistry model) centered over Europe. Both models are three-dimensional (3D) Eulerian models and describe atmospheric transport based on the actual meteorological conditions for 1996. Boundary values of the chemical species for the regional model integrations are supplied by the global model. This paper assesses the importance of long-range Northern Hemispheric transport of ozone and its precursors to calculated concentrations at different height levels over Europe. Calculated 1996 ozone (O3) levels show good accordance with measurements for most of the year, but with a tendency to overestimate O3 at coastal cites. Sensitivity studies have been made with 2010 emission scenarios based on current legislation and reduction plans for Europe and USA, and IPCC scenario WP92a for the rest of the world. Significant reductions in emissions are expected in Europe and North America while increases are expected in other areas, and in particular over Southeast Asia. Model results show a general increase of the global tropospheric ozone levels with significant regional differences. Over Europe, an increase of free tropospheric ozone levels of the order of 10 ppbv can be expected in summer, resulting in boundary layer ozone levels over Europe of the order of 2 ppbv higher than with present free tropospheric levels. Even so, it can be expected that the ozone threshold values in Europe will be much less frequently exceeded in the future as a result of the foreseen reductions in the European emissions of ozone precursors.

A multi‐model study of the hemispheric transport and deposition of oxidised nitrogen

Fifteen chemistry-transport models are used to quantify, for the first time, the export of oxidised nitrogen (NOy) to and from four regions (Europe, North America, South Asia, and East Asia), and to estimate the uncertainty in the results. Between 12 and 24% of the NOx emitted is exported from each region annually. The strongest impact of each source region on a foreign region is: Europe on East Asia, North America on Europe, South Asia on East Asia, and East Asia on North America. Europe exports the most NOy, and East Asia the least. East Asia receives the most NOy from the other regions. Between 8 and 15% of NOx emitted in each region is transported over distances larger than 1000 km, with 3–10% ultimately deposited over the foreign regions.

Road traffic emissions - predictions of future contributions to regional ozone levels in Europe

Abstract As part of the European Commission research project “Assessment of policy instruments for efficient ozone abatement strategies in Europe”, detailed emission projections have been developed for the year 2010 based upon currently adopted measures, and feasible reductions. For road-traffic emissions this projection considers passenger cars, light- and heavy-duty vehicles, mopeds and motorcycles. Here we present model calculations made with the EMEP 3-D Eulerian model to illustrate the relative contribution of each of these road-traffic sectors to ozone concentrations across Europe. The model is run for a six-month period, April–September 1996. The model results clearly suggest that further reduction in road-traffic emissions beyond currently planned measures would be beneficial in reducing ozone over Europe, particularly in the case of heavy-duty vehicles and evaporative emissions. These results do of course depend on the estimated emissions in each sector for the year 2010, and we show that this is a major source of uncertainty in such scenario calculations

Role of spatial and temporal variations in the computation of radiative forcing due to sulphate aerosols: A regional study

A high-resolution regional model for sulphate aerosols is used to investigate the effects of spatial and temporal averaging of radiative forcing. Mie theory is used to calculate the aerosol optical properties. The strong hygroscopic growth with increasing relative humidity is taken into account. The results for the regional area selected in our study (Europe and much of the North Atlantic) show that earlier global studies may have underestimated the magnitude of the radiative forcing due to sulphate aerosols by up to 30–40% due to coarse spatial and/or temporal resolution, at least over certain regions. This underestimation in global models of the water uptake is important for all strongly scattering hygroscopic aerosols. Our results imply that representation of relative humidity at even higher spatial resolution than used in this study may be of importance. This could be incorporated in models using subgrid-scale parametrizations of the relative humidity. Copyright

Calculation of ozone and other pollutants for the summer, 1996

Presents results for April‐September 1996 from the Multi‐layer Atmospheric CHemistry model, Oslo (MACHO), a regional scale photo‐chemistry model, and compares to measurements. Initial and lateral boundary concentrations are provided by a global CTM (chemical tracer model). As a base run, monthly averaged concentrations for June 1996 are used as initial and lateral boundary concentrations. The sensitivity of the interior model domain to the lateral boundaries is analyzed by comparing the base run with a model run with lateral boundary concentrations updated at six‐hour intervals. In the boundary layer over Europe, differences between the two runs are small both for accumulated excesses and for concentrations on individual days, indicating that ozone levels here are determined predominantly by local European scale sources. in the free troposphere, however, the effects of the lateral boundary concentrations are shown to be significant.

Impact of intercontinental pollution transport on North American ozone air pollution: an HTAP phase 2 multi-model study

The recent update on the US National Ambient Air Quality Standards (NAAQS) of the ground-level ozone (O3/ can benefit from a better understanding of its source contributions in different US regions during recent years. In the Hemispheric Transport of Air Pollution experiment phase 1 (HTAP1), various global models were used to determine the O3 source–receptor (SR) relationships among three continents in the Northern Hemisphere in 2001. In support of the HTAP phase 2 (HTAP2) experiment that studies more recent years and involves higher-resolution global models and regional models’ participation, we conduct a number of regional-scale Sulfur Transport and dEposition Model (STEM) air quality base and sensitivity simulations over North America during May–June 2010. STEM’s top and lateral chemical boundary conditions were downscaled from three global chemical transport models’ (i.e., GEOS-Chem, RAQMS, and ECMWF C-IFS) base and sensitivity simulations in which the East Asian (EAS) anthropogenic emissions were reduced by 20 %. The mean differences between STEM surface O3 sensitivities to the emission changes and its corresponding boundary condition model’s are smaller than those among its boundary condition models, in terms of the regional/period-mean (<10 %) and the spatial distributions. An additional STEM simulation was performed in which the boundary conditions were downscaled from a RAQMS (Realtime Air Quality Modeling System) simulation without EAS anthropogenic emissions. The scalability of O3 sensitivities to the size of the emission perturbation is spatially varying, and the full (i.e., based on a 100% emission reduction) source contribution obtained from linearly scaling the North American mean O3 sensitivities to a 20% reduction in the EAS anthropogenic emissions may be underestimated by at least 10 %. The three boundary condition models’ mean O3 sensitivities to the 20% EAS emission perturbations are ~8% (May–June 2010)/~11% (2010 annual) lower than those estimated by eight global models, and the multi-model ensemble estimates are higher than the HTAP1 reported 2001 conditions. GEOS-Chem sensitivities indicate that the EAS anthropogenic NOx emissions matter more than the other EAS O3 precursors to the North American O3, qualitatively consistent with previous adjoint sensitivity calculations. In addition to the analyses on large spatial–temporal scales relative to the HTAP1, we also show results on subcontinental and event scales that are more relevant to the US air quality management. The EAS pollution impacts are weaker during observed O3 exceedances than on all days in most US regions except over some high-terrain western US rural/remote areas. Satellite O3 (TES, JPL–IASI, and AIRS) and carbon monoxide (TES and AIRS) products, along with surface measurements and model calculations, show that during certain episodes stratospheric O3 intrusions and the transported EAS pollution influenced O3 in the western and the eastern US differently. Free-running (i.e., without chemical data assimilation) global models underpredicted the transported background O3 during these episodes, posing difficulties for STEM to accurately simulate the surface O3 and its source contribution. Although we effectively improved the modeled O3 by incorporating satellite O3 (OMI and MLS) and evaluated the quality of the HTAP2 emission inventory with the Royal Netherlands Meteorological Institute–Ozone Monitoring Instrument (KNMI–OMI) nitrogen dioxide, using observations to evaluate and improve O3 source attribution still remains to be further explored.

Effects of ship emissions on European ground-level ozone in 2020.

In recent decades land-based emissions of air pollutants have been substantially reduced over Europe. At the same time emissions from shipping have continued to grow globally. Emissions from international shipping in sea areas surrounding Europe now contribute about 30% of the EU27 emissions of sulphur and NOx and affect ozone levels all over Europe. Although ozone levels are expected to decrease in most parts of Europe, prognoses for 2020 levels are still above what is considered as threshold values. A growing portion of these impacts can be attributed to emissions from international shipping. This paper presents an evaluation of the impacts on ozone levels in the European mainland due to emissions from international shipping. Calculations are carried out under recent (2004) conditions and for a scenario in 2020, where further emission reductions are applied to land based emissions while the ships emissions increase according to their expected growth in transport volumes, without additional technical reduction measures. Impacts are considered with respect to the formation of ground-level ozone, presented as somo35. We investigate the effect of different shipping emission sources, in particular, international shipping inside the 12 mile zone from the coast, emissions from ships outside the 12 mile zone with EU flags and emissions from ships under other flags. It is shown that contributions from EU ships and non-EU and ships outside the 12 mile zone are about equal in magnitude. Corrected for source strength, the largest effect relative to source strength is from emissions within the 12 mile zone. Here ozone titration may cause reductions in somo35 of more than 10% in some countries, or increases of 5% or more elsewhere.

Regional Modelling of Tropospheric Ozone

Atmospheric transport and chemistry models are an essential part of assessing ozone abatement. Such models allow a quantification of both the levels of ozone concentration across the whole of Europe, and of the relative effectiveness of different control measures. In this study, two photochemical models of the European Monitoring and Evaluation Programme (EMEPl) have been used to investigate the effects of emission control scenarios and to assess the contribution of specific source sectors to ozone formation over Europe. In a first step, the status quo of ozone concentrations was calculated for the base year 1990 and the trend scenario 2010, showing that even though precursor emissions were reduced significantly, ozone thresholds were exceeded to a large extent. Data from these models were also used as inputs for the emission-optimisation (Chap. 7), economic evaluation (Chap.s 9 & 10), and for more local modelling (Chap. 8). An important application of the Lagrangian model was the provision of sourcereceptor-matrices for the optimisation by the means of calculating matrices to relate emissions to ozone formation for a 5-year average (see Sect. 6.5).

Socio-economic Impacts—Air Quality

In the North Sea region, poor air quality has serious implications for human health and the related societal costs are considerable. The state of air pollution is often used as a proxy for air quality. This chapter focuses on the two atmospheric pollutants of most significance to human health in Europe—particulate matter and ground-level ozone. These are also important ‘climate forcers’. In the North Sea area, the effects on air quality of emission changes since preindustrial times are stronger than the effects of climate change. According to model simulations, this is also the case for future air quality in the North Sea region, but substantial variation in model results implies considerable uncertainty. Short-term events such as heat waves can have substantial impacts on air quality and some regional climate models suggest that heat waves may become more frequent in the coming decades. If the reductions in air pollutant emissions expected through increasingly stringent policy measures are not achieved, any increase in the severity or frequency of heat waves may have severe consequences for air quality. Climate and air quality interact in several ways and mitigation optimised for a climate or air quality target in isolation could have synergistic or antagonistic effects.