Meteorological Factors Influencing the Radioactive Deposition in Finland after the Chernobyl Accident

Abstract

After the accident at the Chernobyl nuclear plant on 26 April 1986, much of Europe was affected by radioactive pollution. The first releases were transported toward Scandinavia, where most of the fallout was attributable to wet deposition. This study analyzes the synoptic scale and mesoscale meteorological conditions influencing the transport, and the meteorological factors related to the observed fallout in southern Finland. The study focuses on the role of rainfall in the final deposition onto the ground, studied using weather radar data. The results demonstrate that, although the large scale transport from Chernobyl could be roughly estimated by simple methods using routine synoptic data, sonic essential smaller-scale features could not be understood before an isentropic trajectory analysis, together with the conceptual model of a cyclone and its related conveyor belts, was applied. The main result of the study was the good correlation between the radioactive fallout and the corresponding areal distribution of rainfall measured by a weather radar.