Fog Causality, Reversibility, and Forming Mechanisms.*

The presence of fog significantly impacts transportation safety, agriculture, and daily planning. However, fog prediction remains challenging due to our limited understanding of the complex, multiscale processes that govern its formation, duration, and dissipation. The study aims to test whether there is causality in the fog cascade, to what extent this causality can be inferred from the turbulent series, and whether this reversibility/causality highlights the formation mechanism. To address this, we examined data from eight fog events with different formation mechanisms that were recorded and identified on Sable Island over the month of July 2022, as part of the Fog and Turbulence Interactions in the Marine Atmosphere (FATIMA) field campaign that was conducted in the Nova Scotia region. Here, we apply techniques from time series analysis including continuous wavelet transforms to explore the causality and statistical reversibility of fog events, which involve phase transitions that can be considered as non-reversible. Visibility is used as a surrogate for fog and turbulent kinetic energy is explored as a variable that can disrupt fog formation. This research provides valuable insights into the underlying dynamics of fog occurrence, paving the way for improved fog prediction and response strategies.