ABSTRACT

Atmospheric transport, dispersion, and deposition models (ATDMs) can support decision-making during nuclear emergencies; however, uncertainties in the ATDM results need to be carefully evaluated. To investigate the uncertainties derived from meteorological forecast inputs, we conducted three-day forecast simulations every day for one year with hypothetical releases of radionuclides (one-hour releases every 6 h) from a nuclear facility. The forecast outputs were compared with the analysis outputs during the same period. The difference between the outputs is treated as the uncertainty in the forecasts and is represented as an angle based on the discrepancy in the plume directions between the analysis and forecast outputs. Using meteorological inputs made by Japan Meteorological Agency, the discrepancy angle (Ang) increased by approximately 10${ }^{\circ }$ per day on an annual average basis. Meanwhile, the Ang values were occasionally 4–5 times higher than the annual average during short time periods. Since the Ang time series show seasonal and diurnal changes, the statistical characteristics likely depend on the geographical and meteorological conditions, as well as the types of meteorological inputs. Additionally, a main factor in the uncertainty is the wind-direction difference between the analysis and forecast outputs on scales of more than or less than 100 km.

摘要

大气传输、扩散和沉积模型 (ATDM) 可以支持核紧急情况期间的决策；然而，需要仔细评估 ATDM 结果中的不确定性。为了研究气象预报输入的不确定性，我们在一年中每天进行为期三天的预报模拟，假设核设施的放射性核素释放（每 6 小时释放一小时）。将预测输出与同期的分析输出进行比较。输出之间的差异被视为预测中的不确定性，并表示为基于分析和预测输出之间羽流方向差异的角度。使用日本气象厅提供的气象输入，差异角 (Ang) 增加了约 10${ }^{\circ }$每天平均每年。同时，在短时间内，Ang 值偶尔会比年平均值高 4-5 倍。由于 Ang 时间序列呈现季节性和昼夜变化，统计特征可能取决于地理和气象条件，以及气象输入的类型。此外，不确定性的一个主要因素是大于或小于 100 公里尺度的分析和预测输出之间的风向差异。