The effect of calm conditions and wind intervals in low wind speed on atmospheric dispersion factors

► This study is meant to analyze the effects of calm and wind intervals on the atmospheric dispersion factors. ► A Gaussian plume model and XOQDOQ program with statistical methods were used. ► The atmospheric dispersion factors can be affected by calm definitions and wind speed intervals. The effects of wind speed defined for calm conditions and wind interval at a low wind speed on the atmospheric dispersion factors (ADFs) using a Gaussian plume model, statistical approach, and XOQDOQ program were analyzed in this study. There was a statistically significant difference in the ADFs calculated on 1000-m concentric circles from the release when the wind speed is adjusted from 0.5m/s to 0.2m/s for calm conditions. If a dispersion model as the input of the joint frequency distribution is used for an estimation of ADFs, it was found that the ADFs were affected by the classification of wind intervals at a low wind speed of lower than 2.0m/s. To minimize the effect of wind speed intervals at a low wind speed to ADFs, the wind interval should be adjusted considering the frequency distribution of a low wind speed and adjusted in either way to narrow the interval for a low wind speed or widen it for a high wind speed.