Climatology and trends of fog in the Svalbard region

Fog is a common feature of the lower atmosphere in the Arctic, yet its long-term variability, seasonal changes, and sensitivity to rapid climate warming remain poorly known. Using meteorological data from five Svalbard stations from 1970 to 2020, we analyse seasonal fog occurrence, fog type (advection versus radiation), temperature, wind patterns. We also use sulphate aerosol data from one Svalbard station to investigate aerosol conditions.

High fog frequencies (7-15 %) are seen at the stations located on smaller islands in the vicinity of Svalbard (Janmayen, Bjørnøya, Hopen). The other two sites, located at Spitsbergen (Svalbard Airport, Ny-Ålesund), show substantially lower fog frequencies (0-4%). During summer, the fog frequency is highest for all stations, with radiation fog dominating at Spitsbergen sites while on the island stations, both advection fog and radiation fog is types are common. During winter, advection fog is predominant from cold, northerly to northeasterly marine airflows at most sites. The temperature during advection fog in winter is colder than during the formation of radiation fog. Spring and autumn seasonal represent transitional periods, with both fog types occurring but at lower overall frequencies. The wind direction during fog change seasonally, shifting from northerly/easterly in winter to southerly/westerly in summer.

Fog occurrence has decreased at most sites between 1970 and 2020. The drop is especially noticeable at Janmayen and Bjørnøya. The fog frequency at the Spitsbergen sites is also declining but with a weaker decreasing trend. The analysis shows that it is advection fog that is decreasing and not radiation fog. Regional warming, reduced sea-ice extent, and lower Arctic aerosol loading could be responsible for this decreasing trends. These results indicate that fog is sensitive to climate change in the Arctic. It changes visibility, the local radiation budget, and the way air and sea interact in an environment that is changing quickly.