Fog Intermittency and Critical Behavior

One of the key stochastic features that affects the duration and moisture content of fog occurrence is its intermittency, the alternating periods of fog and no-fog. Here, intermittency is studied using visibility data collected on Sable Island, Canada during the Fog and Turbulence Interactions in the Marine Atmosphere (FATIMA) campaign in July of 2022. In addition to visibility, to establish links between fog intermittency and the underlying atmospheric variables, relative humidity (related to the formation of fog) and turbulent kinetic energy (related to the dissipation of fog) are also studied in the same framework. Qualitative dynamical features of the time series are identified, and their binary approximations are used to isolate their clustering behavior from amplitude variations. It is shown that many stochastic features describing visibility are bounded by those of relative humidity and turbulent kinetic energy. In addition, the visibility time series displays features consistent with Pomeau–Manneville Type-III intermittency, a sporadically random process. Lastly, the on-off and off-on switching properties are analyzed to investigate whether self-organized criticality (SOC) describes fog occurrence. In the visibility time series, universal stochastic patterns expected for an SOC system is observed, albeit with intermittency corrections. Lastly, a simplistic physical model is proposed to illustrate the phase transitions and criticality of fog.

This work was funded by the Grant N00014-21-1-2296 (Fatima Multidisciplinary University Research Initiative) of the Office of Naval Research, administered by the Marine Meteorology and Space Program.