TURBULENCJA OPTYCZNA W CENTRUM MIASTA W ŚWIETLE POMIARÓW SCYNTYLOMETRYCZNYCH NA PRZYKŁADZIE ŁODZI.

This study considers the temporal variability of the refractive index of air structure parameter Cn2, which could be considered as the measure of optical turbulence intensity. In addition, the principals of scintillation method were presented. On the basis of scintillometer data, i.e. the averaged path Cn2, the annual and diurnal course of the optical turbulence in the city centre was analysed. The highest frequency of strong optical turbulence (ca. 40%) was observed in spring and summer, with maximum around May and June. In the whole study period, weak turbulence occurred rarely. This might result from the urban heat island, which intensifies the heat exchange between the urban surface and the overlying air. This effect contributes to the enhanced Cn2. Additionally, the increased roughness of urban areas can lead to more frequent generation of mechanical turbulence. [ABSTRACT FROM AUTHOR]