World marine fog analysis based on 58‐years of ship observations

This study presents the first global-scale comprehensive climatology of marine fog and is based on ICOADS ship present weather observations for the period 1950-2007. In general, the median marine fog occurrence away from the polar oceans is low (0.2%). Substantially greater marine fog occurrences are limited to four regions, not including the polar region. Fog occurrence maxima along the western side of the sub-polar ocean gyre occur during the warm season and over the shelf, which includes one centred over the Northwest Pacific Kuril Islands (60%) and one over the Northwest Atlantic Grand Banks (45%), while a third lies over the Argentinean shelf break. Fog maxima over seven marginal seas occur over the Okhotsk Sea, Sea of Japan, Yellow Sea, South China Sea, Nova Scotia, North Sea, and Baltic Sea. Five wind-driven coastal upwelling zone maxima comprise the California-Oregon, Namibia-South Africa, Peru, Morocco and Arabian regions. Maximum upwelling fog occurrence during the warm season was found to be inversely proportional to the minimum sea surface temperature (SST). Most fog maximum occurrence locations lie over SST minima in shallow water during the warm season and are capped by a stable lower atmosphere. Positive correlations (up to 0.79) were found between 5-year moving averages of fog in the Kuril Islands and the North Pacific Oscillation. Five-year moving averages of fog in the Grand Banks were positively and significantly correlated (up to 0.56), with the North Atlantic Oscillation represented by the sea level pressure difference between Gibraltar and Reykjavik. In contrast, 5-year moving averages of fog in the Grand Banks and the Atlantic Multidecadal Oscillation index were negatively and significantly correlated (up to -0.75).