Climatologie des brouillards epais dans la plaine du Po (Italie Septentrionnelle).

Aim of this work was to provide a first picture of the thick fog frequency, i.e. with horizontal visibility lower than 100 meters, in the Po plain, condition which causes remarkable problems to the aerial and motor tra ic. The analysis of this phenomenon has been possible by the study of the SYNOP messages, provided by the Meteorological Service of the Air Force in stations of survey which had cadence every three hours, continuous surveys or higher than 90% of the total potential. Therefore, the number of stations selected for the analysis has got down up to 15. Moreover, quite homogeneously distributed in the padano-veneto territory and along the coast of the high Adriatic Sea. The analysis was directed towards a calculation of a number of days with thick fog and to the evidence of the thirty-year tendencies concerning the phenomenon. The study of the minimum monthly minimum temperatures has allowed to understand that the increase in temperature registered in the undergoing study's period partly explains the general tendency to the decrease of the phenomenon but does not completely clarify the significant present differences between stations having the same increase in the temperatures. It is then possible to assume that the local morphology and its changes in the analysed thirty-year period may have a strong weight in explanations of the above-mentioned differences.