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Abstract:
We intercompare simulations of the dispersion of aerosol and gaseous radionuclides (137Cs and 131I) driven by a four-member ensemble of (re-)analysis and forecast datasets to quantify statistical and systematic uncertainties. The Lagrangian particle dispersion model FLEXPART 10.4 and FLEXPART-WRF are driven by 6-hourly data from NCEP Global Forecast System (GFS) and Final Analysis (FNL), at spatial resolutions of 0.5 and 0.25 degrees. In addition, for running FLEXPART-WRF, the FNL and ECMWF Reanalysis v5 (ERA5) were first downscaled, to the finer resolutions of 10 km and 1 hour, using the Weather Research and Forecasting (WRF) model. A total of 365 experiments (each day of 2019) were conducted to produce hourly simulations at the spatial resolution of 10 km in 14 vertical levels through 96 hours after a fictitious nuclear power plant accident at Barakah, UAE, in an effort to study the potential risks to the population in the state of Qatar. The source term was scaled to the maximum estimates of the radioactive materials from the Fukushima accident in 2011 (0.042 kg of 131I and 7 kg of 137Cs), released within 24 hours after the accident. We intercompare radionuclide age spectra, cumulative deposition, and population exposure, seasonal variance, and investigate the degree of variability and correlation between ensemble members. Results show that the computational particles corresponded to dense 131I clouds enter Qatar more frequently within 10 to 20 hours after the accident. The cumulative distribution of simulated 137Cs depositions indicates that more than 80% of 137Cs depositions occurs within 75 hours after the accident, with a hotspot in the southeast of Qatar. GFS and ERA-5 show a high degree of correlation, whereas FNL is different. We also observe seasonal variation due to deposition and boundary layer development.
