322 research outputs found
Modelling the global atmospheric transport and deposition of radionuclides from the Fukushima Dai-ichi nuclear accident
No full text
Modelling the global atmospheric transport and deposition of radionuclides from the Fukushima Dai-ichi nuclear accident
No full textWe 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 <sup>131</sup>I and <sup>137</sup>Cs, and removal processes through precipitation, particle sedimentation and dry deposition. In addition, we simulated the release of <sup>133</sup>Xe, 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 <sup>131</sup>I 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<sup>-2</sup>. We also estimated the inhalation and 50-year dose by <sup>137</sup>Cs, <sup>134</sup>Cs and <sup>131</sup>I to which the people in Japan are exposed
GPU-accelerated atmospheric chemical kinetics in the ECHAM/MESSy (EMAC) Earth system model (version 2.52)
No full textThis paper presents an application of GPU accelerators in Earth system
modeling. We focus on atmospheric chemical kinetics, one of
the most computationally intensive tasks in climate–chemistry model simulations. We developed a software package that automatically
generates CUDA kernels to numerically integrate atmospheric chemical kinetics in the global climate model ECHAM/MESSy Atmospheric
Chemistry (EMAC), used to study climate change and air quality scenarios. A source-to-source compiler outputs a CUDA-compatible
kernel by parsing the FORTRAN code generated by the Kinetic PreProcessor (KPP) general analysis tool. All Rosenbrock methods that
are available in the KPP numerical library are supported.Performance evaluation, using Fermi and Pascal CUDA-enabled GPU accelerators, shows achieved speed-ups of 4. 5 × and
20. 4 × , respectively, of the kernel execution time. A node-to-node real-world production performance comparison shows a 1. 75 × speed-up
over the non-accelerated application using the KPP three-stage Rosenbrock solver. We provide a detailed description of the code
optimizations used to improve the performance including memory optimizations, control code simplification, and reduction of idle
time. The accuracy and correctness of the accelerated implementation are evaluated by comparing to the CPU-only code of the
application. The median relative difference is found to be less than 0.000000001 % when comparing the output of the accelerated
kernel the CPU-only code.The approach followed, including the computational workload division, and the developed GPU solver code can potentially be used as the
basis for hardware acceleration of numerous geoscientific models that rely on KPP for atmospheric chemical kinetics applications
North Atlantic Oscillation model projections and influence on tracer transport
No full textThe North Atlantic Oscillation (NAO) plays an important role in the climate variability of the Northern Hemisphere with significant consequences on pollutant transport. We study the influence of the NAO on the atmospheric dispersion of pollutants in the near past and in the future by considering simulations performed by the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model. We analyze two model runs: a simulation with circulation dynamics nudged towards ERA-Interim reanalysis data over a period of 35 years (1979–2013) and a simulation with prescribed Sea Surface Temperature (SST) boundary conditions over 150 years (1950–2099). The model is shown to reproduce the NAO spatial and temporal variability and to be comparable with observations. We find that the decadal variability in the NAO, which has been pronounced since 1950s until 1990, will continue to dominate in the future considering decadal periods, although no significant trends are present in the long term projection (100–150 years horizon). We do not find in the model projections any significant temporal trend of the NAO for the future, meaning that neither positive or negative phases will dominate. Tracers with idealised decay and emissions are considered to investigate the NAO effects on transport; it is shown that during the positive phase of the NAO, the transport from North America towards northern Europe is stronger and pollutants are shifted northwards over the Arctic and southwards over the Mediterranean and North Africa, with two distinct areas of removal and stagnation of pollutants
Global risk from the atmospheric dispersion of radionuclides by nuclear power plant accidents in the coming decades
No full textWe 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
Projection of North Atlantic Oscillation and its effect on tracer transport
No full textThe 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
Influence of the North Atlantic Oscillation on air pollution transport
No full textAbstract. We examined the influence of the North Atlantic Oscillation (NAO) on the atmospheric dispersion of pollution by computing the emission, transport and removal of insoluble gaseous and water-soluble aerosol tracers, tagged by the continent of origin. We simulated a period of 50 yr (1960–2010), using the ECHAM/MESSy 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 tracer concentrations over the northwestern Atlantic Ocean and across northern Europe, and with European trace gases and aerosols beyond the arctic circle. Our results indicate marked differences and partly reversed correlations for the insoluble gas and the soluble aerosol tracers. We find a strong anti-correlation over western and central Europe between European pollutant gas and aerosol concentrations and the phase of the NAO.
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Projection of North Atlantic Oscillation and its effect on tracer transport
No full textThe 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 north-eastward 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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