Australian Fog Climatology, Synoptic Patterns and Trends

Fog is a surface level cloud that reduces visibility and can be hazardous to the aviation and transport industries. Fog is highly localized in time and space, making it difficult to observe. Most fog climatologies are based on station data particularly from airports where visibility measurements are taken. In this study, we evaluate fog representation in a high-resolution reanalysis, BARRA-C2, over Australia by comparing fog frequency in BARRA-C2 with airport station observations. While BARRA-C2 generally overestimates fog frequency relative to station-based observations, the seasonality and magnitude of fog is similar at most locations. Thus, we conclude that BARRA-C2 is useful for fog analysis. We show fog frequency and trends in BARRA-C2 over Australia from 1980–2024. We find statistically significant increasing trends in fog frequency along the southern coast of Australia and decreasing trends in parts of Northern Australia. We also examine fog frequencies under different synoptic weather types to show which synoptic conditions are more prone to fog. Finally, we assess trends in meteorological variables that are conducive to fog formation including low-level inversions, pressure and humidity.