Meteorological characteristics of the Po Valley fog

Abstract

The meteorological situation during the first joint field campaign from 10-17 November 1989 of the EUROTRAC subproject GCE is discussed. The synoptic situation is illustrated by weather charts and satellite pictures. Backtrajectories were calculated in order to identify the origins of airmasses reaching the observation point. Model calculations were performed to explain the observed counter current channelling in the Po Valley. For the 5 different fog episodes observed, fog liquid water content, temperature, humidity, and wind speed are displayed as a function of height. Possible reasons for formation, evolution, and dissipation are discussed. It was found that the radiation effects only played a minor role. Most of the time, the fog at the observation site was either advected or formed due to the advection of cold or moist air.