Characterisation of influential mechanisms in the life cycle of fog: a study of two extreme events at airports in central-eastern Argentina

Reduced visibility due to fog is a major disruptor of global air traffic, leading to flight cancellations, delays and diversions. To enhance forecasting and mitigate these losses, a thorough understanding of the physical mechanisms governing the life cycle of fog is essential. This study aims to advance this understanding in Argentina, focusing on events where fog simultaneously affected the operations of several airports and, therefore, all the air traffic of the country. Two specific cases, one of extreme duration and one unexpected by forecasters, from different seasons, were analysed using aeronautical meteorological observations (Meteorological Terminal Aviation Report, METAR), radiosondes, Geostationary Operational Environmental Satellite-16 (GOES-16) satellite images and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5) reanalysis data. Satellite techniques for detecting low clouds and fog were particularly effective at night but had limitations in distinguishing between fog and low stratus. The study identified multiple mechanisms operating at various scales that contribute to fog formation and dissipation. Both events were characterised by frontal passages – cold in the summer and warm in the winter – accompanied by associated temperature and moisture advections. Various local factors, despite similar synoptic conditions, influenced boundary layer processes at smaller scales, resulting in distinct fog behaviour at each location. These findings highlight the complexity of fog forecasting, fog being driven by multiple interacting processes across different scales, as well as the constraints of current observational systems and numerical models.