Validation Study for an Atmospheric Dispersion Model, Using Effective Source Heights Determined from Wind Tunnel Experiments in Nuclear Safety Analysis

For more than fifty years, atmospheric dispersion predictions based on the joint use of a Gaussian plume model and wind tunnel experiments have been applied in both Japan and the U.K. for the evaluation of public radiation exposure in nuclear safety analysis. The effective source height used in the Gaussian model is determined from ground-level concentration data obtained by a wind tunnel experiment using a scaled terrain and site model. In the present paper, the concentrations calculated by this method are compared with data observed over complex terrain in the field, under a number of meteorological conditions. Good agreement was confirmed in near-neutral and unstable stabilities. However, it was found to be necessary to reduce the effective source height by 50% in order to achieve a conservative estimation of the field observations in a stable atmosphere

Study on long-term radiation exposure analysis after the Fukushima Dai-ichi nuclear power plant accident: validation of the EU long-term radiation exposure model (ERMIN)

The Fukushima Dai-ichi nuclear power plant accident led to the dispersion of radioactivematerial by windthat resulted in soil and air pollution over a wide area. Even now, more than 150,000 people in Fukushimaprefecture are still relocated from their homes. In order to estimate how long such relocation might continue,we estimated radiation exposures for the 10 years following the accident that occurred on 12 March2011, using European model for inhabited areas (ERMIN) developed by a partnership of several Europeanorganizations. We validated the estimated results of long-term radiation exposure with the observeddata at 1, 2 and 3 years after the nuclear accident. We analyzed the deposition velocity and re-suspensioncoefficient using the observed data on air concentration, amount of falling dust and soil contamination,and compared them with the published data

Diagnosis of tropospheric moisture over Saudi Arabia and influences of IOD and ENSO.

A diagnostic study of atmospheric moisture data over Saudi Arabia derived from a 43-yr National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis revealed that moisture convergence in the lower troposphere and divergence in and above the middle troposphere occurs throughout the year. Although the amount of precipitable water content in the middle troposphere is high, precipitation is less than expected over this semiarid region during a boreal summer monsoon season because of strong moisture divergence. The net tropospheric moisture flux over the arid and semiarid regions of Saudi Arabia shows seasonal and interannual variability. The seasonal variability has a strong semiannual signal with its primary peak February-April and its secondary peak June-August. This pattern is consistent with a similar semiannual signal observed in rainfall climatology. The restricted moisture supply to southwestern Saudi Arabia during summer presumably explains the lack of precipitation in other areas of the country. Winter precipitation, however, is widespread. The increased transport of net atmospheric moisture flux is higher during El Niño and positive Indian Ocean dipole (IOD) phenomena. During these events, influx across the Red Sea (west) side of Saudi Arabia increases. The net flux to the region is reduced by a slight increase of outflux across the Persian Gulf (east) side. Reanalysis data and model-sensitivity experiments show that El Niño or a concurrent positive IOD and El Niño event more strongly amplify net transport than does an independent positive IOD event. The partial-lag correlation analysis with net moisture flux from the Red Sea side shows that the positive IOD mode has a peak correlation coefficient of �0.5 with close to a 5-month lead and that El Niño has a peak correlation coefficient of �0.6 with close to a 2-month lead. © 2006 American Meteorological Society