[en] The Gaussian dispersion model is extensively used to assess the impact of radiation releases. Under changing weather conditions, the model may not unfold the actual scenario. The Mathew-Adpic system of numerical codes is used to conduct a theoretical study of the isodose patterns under changing meteorological parameters due to an assumed continuous unit release of ⁴¹Ar. It is observed that a distorted shape of isodose rate pattern results when the weather category changes after prolonged stable conditions associated with drastic change in the wind sector. The distortion in the isodose rate pattern is transitory and lasts for about an hour. (author)