We modeled the global atmospheric dispersion and deposition of radionuclides released from the Fukushima Dai-ichi nuclear power plant accident. The EMAC atmospheric chemistry – general circulation ...model was used, with circulation dynamics nudged towards ERA-Interim reanalysis data. We applied a resolution of approximately 0.5 degrees in latitude and longitude (T255). The model accounts for emissions and transport of the radioactive isotopes 131I and 137Cs, and removal processes through precipitation, particle sedimentation and dry deposition. In addition, we simulated the release of 133Xe, a noble gas that can be regarded as a passive transport tracer of contaminated air. The source terms are based on Chino et al. (2011) and Stohl et al. (2012); especially the emission estimates of 131I are associated with a high degree of uncertainty. The calculated concentrations have been compared to station observations by the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO). We calculated that about 80% of the radioactivity from Fukushima which was released to the atmosphere deposited into the Pacific Ocean. In Japan a large inhabited land area was contaminated by more than 40 kBq m-2. We also estimated the inhalation and 50-year dose by 137Cs, 134Cs and 131I to which the people in Japan are exposed.
We examined the influence of the North Atlantic Oscillation (NAO) on the atmospheric dispersion of pollution by computing the emission, transport and removal of idealized insoluble gaseous and ...water-soluble aerosol tracers, tagged by the continent of origin. We simulated a period of 50 yr (1960-2010), using the ECHAM5/MESSy1 atmospheric chemistry (EMAC) general circulation model. The model accounts for anthropogenic, biogenic and biomass burning sources, removal of trace gases through OH oxidation, and precipitation, sedimentation and deposition of aerosols. The model is shown to reproduce the observed spatial features of the NAO, moisture transports and precipitation. During high NAO phase seasons the axis of maximum westerly North American trace gas transports extends relatively far to the north and east over Europe. The NAO phase is significantly correlated with North American insoluble gas and soluble aerosol tracer concentrations over the northwestern Atlantic Ocean and across northern Europe, and with European trace gases and aerosols over Africa and north of the Arctic circle. We find a strong anti-correlation between the phase of the NAO and European pollutant gas concentration over western and central Europe.
We investigate the impact of implementing an up-to-date and detailed land cover dataset in high-resolution regional climate simulations. We used the Weather Research Forecast (WRF) model version ...3.6.1 on a high horizontal resolution of 5 km × 5 km, with 29 vertical levels, covering mainland Europe. We performed simulations within the year 2050, using future Representative Concentration Pathway 8.5 mid-century projections, for 2 winter (January, February) and the 2 summer months (June, July) to investigate the seasonal dependency of the impact of the land cover datasets on and their interaction with the different meteorological conditions prevailing in summer and winter. We compare simulations using the CORINE Land Cover dataset (100 × 100 m) and the standard United States Geological Survey (USGS) (~ 1 × 1 km) land use data for the same periods. Our analysis shows that simulated meteorological variables (temperature at 2 m, wind speed, sensible and latent heat fluxes and PBL heights) differ significantly between the WRF simulations, linked to the land cover parameterization. We quantify and discuss the modelling uncertainties arising from surface-type classifications and motivate the use of high resolution, and continuously updated land use inventories in climate modelling, especially for future projections. Our findings are particularly important for the summer season and over large urban centers, and we strongly recommend the use of high-quality resolution land use data in modelling experiments studying heat waves in synergy with the urban heat island phenomenon and land–surface interactions.
We estimate the global risk from the release and atmospheric dispersion of radionuclides from nuclear power plant accidents using the EMAC atmospheric chemistry–general circulation model. We included ...all nuclear reactors that are currently operational, under construction and planned or proposed. We implemented constant continuous emissions from each location in the model and simulated atmospheric transport and removal via dry and wet deposition processes over 20 years (2010–2030), driven by boundary conditions based on the IPCC A2 future emissions scenario. We present global overall and seasonal risk maps for potential surface layer concentrations and ground deposition of radionuclides, and estimate potential doses to humans from inhalation and ground-deposition exposures to radionuclides. We find that the risk of harmful doses due to inhalation is typically highest in the Northern Hemisphere during boreal winter, due to relatively shallow boundary layer development and limited mixing. Based on the continued operation of the current nuclear power plants, we calculate that the risk of radioactive contamination to the citizens of the USA will remain to be highest worldwide, followed by India and France. By including stations under construction and those that are planned and proposed, our results suggest that the risk will become highest in China, followed by India and the USA.
Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This ...makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available aerosol surface area. 137Cs size distribution measurements taken close to the power plant suggested that accumulation-mode (AM) sulfate aerosols were the main carriers of cesium. Hence, 137Cs can be used as a proxy tracer for the AM sulfate aerosol's fate in the atmosphere. In contrast, the noble gas 133Xe behaves almost like a passive transport tracer. Global surface measurements of the two radioactive isotopes taken over several months after the release allow the derivation of a lifetime of the carrier aerosol. We compare this to the lifetimes simulated by 19 different atmospheric transport models initialized with identical emissions of 137Cs that were assigned to an aerosol tracer with each model's default properties of AM sulfate, and 133Xe emissions that were assigned to a passive tracer. We investigate to what extent the modelled sulfate tracer can reproduce the measurements, especially with respect to the observed loss of aerosol mass with time. Modelled 137Cs and 133Xe concentrations sampled at the same location and times as station measurements allow a direct comparison between measured and modelled aerosol lifetime. The e-folding lifetime τe, calculated from station measurement data taken between 2 and 9 weeks after the start of the emissions, is 14.3 days (95 % confidence interval 13.1–15.7 days). The equivalent modelled τe lifetimes have a large spread, varying between 4.8 and 26.7 days with a model median of 9.4 ± 2.3 days, indicating too fast a removal in most models. Because sufficient measurement data were only available from about 2 weeks after the release, the estimated lifetimes apply to aerosols that have undergone long-range transport, i.e. not for freshly emitted aerosol. However, modelled instantaneous lifetimes show that the initial removal in the first 2 weeks was quicker (lifetimes between 1 and 5 days) due to the emissions occurring at low altitudes and co-location of the fresh plume with strong precipitation. Deviations between measured and modelled aerosol lifetimes are largest for the northernmost stations and at later time periods, suggesting that models do not transport enough of the aerosol towards the Arctic. The models underestimate passive tracer (133Xe) concentrations in the Arctic as well but to a smaller extent than for the aerosol (137Cs) tracer. This indicates that in addition to too fast an aerosol removal in the models, errors in simulated atmospheric transport towards the Arctic in most models also contribute to the underestimation of the Arctic aerosol concentrations.
We investigate the spatiotemporal distribution of the radionuclides including
iodine-131 (131I) and cesium-137 (137Cs), transported to Qatar
from fictitious accidents at the upwind Barakah nuclear ...power plant (B-NPP)
in the United Arab Emirates (UAE). To model the dispersion of
radionuclides,
we use the Lagrangian particle–air parcel dispersion model FLEXible
PARTicle
(FLEXPART) and FLEXPART coupled with the Weather Research and
Forecasting model (FLEXPART–WRF). A four-member mini-ensemble of
meteorological inputs is used to investigate the impact of meteorological
inputs on the radionuclide dispersion modeling. The mini-ensemble includes
one forecast dataset (Global Forecast System, GFS) and three (re)analysis datasets (native-resolution and downscaled NCEP final analysis – FNL, as well as downscaled ERA5). Additionally, we
explore the sensitivity of the radionuclide dispersion simulations to
variations in the turbulence schemes, as well as the temporal and vertical
emission profiles, and the location of emission sources. According to the
simulated age spectrum of the Lagrangian particles, radionuclides enter
southern Qatar about 20 to 30 h after release. Most of the radionuclide
deposition in the study area occurs within 80 h after release. The most
populated areas of Qatar coincide with moderate 131I concentrations
and
137Cs deposition, while uninhabited areas in southern Qatar receive
the
highest amounts. A larger number of long-lived particles is found in the
FNL-based simulations, which is interpreted as a greater dispersion of
particles at a greater distance from the emission location. The highest
simulated 131I and 137Cs deposition shows a pronounced
spatiotemporal pattern. The largest impacts are found in the
south and southeast
of Qatar, during the early daytime development of the boundary layer, and
during the cold period of the year. The results show remarkable differences
in the spatiotemporal distribution of 131I and 137Cs simulations
based on the FNL and GFS datasets, which share a common base meteorological
model. As part of a sensitivity analysis involving different model setups,
changing the emission point from B-NPP to Bushehr NPP (Bu-NPP) results in a
reduced transfer of radioactive materials to Qatar, except in the spring
season. Bu-NPP simulations reveal distinct spatial patterns, with peak
131I concentrations and 137Cs deposition observed in northern
and eastern Qatar during winter and spring.
We employ the WRF-Chem model to study summertime air pollution,
the intense photochemical activity and their impact on air quality over the
eastern Mediterranean. We utilize three nested domains with ...horizontal
resolutions of 80, 16 and 4 km, with the finest grid focusing on the
island of Cyprus, where the CYPHEX campaign took place in July 2014.
Anthropogenic emissions are based on the EDGAR HTAP global emission
inventory, while dust and biogenic emissions are calculated online. Three
simulations utilizing the CBMZ-MOSAIC, MOZART-MOSAIC, and RADM2-MADE/SORGAM
gas-phase and aerosol mechanisms are performed. The results are compared with
measurements from a dense observational network of 14 ground stations in
Cyprus. The model simulates T2 m, Psurf, and
WD10 m accurately, with minor differences in WS10 m between
model and observations at coastal and mountainous stations attributed to
limitations in the representation of the complex topography in the model. It
is shown that the south-eastern part of Cyprus is mostly affected by
emissions from within the island, under the dominant (60 %) westerly flow
during summertime. Clean maritime air from the Mediterranean can reduce
concentrations of local air pollutants over the region during westerlies.
Ozone concentrations are overestimated by all three mechanisms
(9 % ≤ NMB ≤ 23 %) with the smaller mean bias (4.25 ppbV)
obtained by the RADM2-MADE/SORGAM mechanism. Differences in ozone
concentrations can be attributed to the VOC treatment by the three
mechanisms. The diurnal variability of pollution and ozone precursors is not
captured (hourly correlation coefficients for O3 ≤ 0.29). This
might be attributed to the underestimation of NOx concentrations by local
emissions by up to 50 %. For the fine particulate matter (PM2.5),
the lowest mean bias (9 µg m−3) is obtained with the
RADM2-MADE/SORGAM mechanism, with overestimates in sulfate and ammonium
aerosols. Overestimation of sulfate aerosols by this mechanism may be linked
to the SO2 oxidation in clouds. The MOSAIC aerosol mechanism
overestimates PM2.5 concentrations by up to
22 µg m−3 due to a more pronounced dust component compared to
the other two mechanisms, mostly influenced by the dust inflow from the
global model. We conclude that all three mechanisms are very sensitive to
boundary conditions from the global model for both gas-phase and aerosol
pollutants, in particular dust and ozone.
Urban areas and industrial facilities, which concentrate the majority of human activity and industrial production, are major sources of air pollutants, with serious implications for human health and ...global climate. For most of these pollutants, emission inventories are often highly uncertain, especially in developing countries. Spaceborne measurements from the TROPOMI instrument, on board the Sentinel-5 Precursor satellite, are used to retrieve nitrogen dioxide (NO2) column densities at high spatial resolution. Here, we use 2 years of TROPOMI retrievals to map nitrogen oxide (NOx = NO + NO2) emissions in Egypt with a top-down approach using the continuity equation in steady state. Emissions are expressed as the sum of a transport term and a sink term representing the three-body reaction comprising NO2 and hydroxyl radical (OH). This sink term requires information on the lifetime of NO2, which is calculated with the use of the CAMS near-real-time temperature and OH concentration fields. We compare this derived lifetime with the lifetime inferred from the fitting of NO2 line density profiles in large plumes with an exponentially modified Gaussian function. This comparison, which is conducted for different samples of NO2 patterns above the city of Riyadh, provides information on the reliability of the CAMS near-real-time OH concentration fields; it also provides some hint on the vertical levels that best represent typical pollution sources in industrial areas and megacities in the Middle East region. In Egypt, total emissions of NOx are dominated by the sink term, but they can be locally dominated by wind transport, especially along the Nile where human activities are concentrated. Megacities and industrial regions clearly appear as the largest sources of NOx emissions in the country. Our top-down model infers emissions with a marked annual variability. By looking at the spatial distribution of emissions at the scale of different cities with different industrial characteristics, it appears that this variability is consistent with national electricity consumption. We detect lower emissions on Fridays, which are inherent to the social norm of the country, and quantify the drop in emissions in 2020 due to the COVID-19 pandemic. Overall, our estimations of NOx emissions for Egypt are 7.0 % higher than the CAMS-GLOB-ANT_v4.2 inventory and significantly differ in terms of seasonality.
The North Atlantic Oscillation (NAO) plays an important role in the climate variability of the Northern Hemisphere, with significant consequences on long-range pollutant transport. We investigate the ...evolution of pollutant transport in the 21st century influenced by the NAO under a global climate change scenario. We use a free-running simulation performed by the ECHAM/MESSy Atmospheric Chemistry (EMAC) model coupled with the ocean general circulation model MPIOM, covering the period from 1950 until 2100. Similarly to other works, the model shows a future northeastward shift of the NAO centres of action and a weak positive trend of the NAO index (over 150 years). Moreover, we find that NAO trends (computed over periods shorter than 30 years) will continue to oscillate between positive and negative values in the future. To investigate the NAO effects on transport we consider carbon monoxide tracers with exponential decay and constant interannual emissions. We find that at the end of the century, the south-western Mediterranean and northern Africa will, during positive NAO phases, see higher pollutant concentrations with respect to the past, while a wider part of northern Europe will, during positive NAO phases, see lower pollutant concentrations. Such results are confirmed by the changes observed in the future for tracer concentration and vertically integrated tracer transport, differentiating the cases of “high NAO” and “low NAO” events.
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