Cold season inversion fog in Salt Lake City: connections to Valley variables and numerical simulations

A comprehensive study on cold season inversion fog at Salt Lake City, Utah, has been performed. First, the connection between stable valley airmasses and fog events was investigated using soundings and reported automated surface observing system (ASOS) data from Salt Lake International Airport (KSLC) for eighteen cold seasons (October to March, during 1997-2015). A chi-square test of independence was performed on identified stable valley airmasses and fog events to determine whether the two are correlated. Conditional probabilities were then computed to investigate the occurrence of fog, given the presence of a stable valley airmass. These probabilities are compared against that of random fog generation in mid-winter. It was concluded that the dependence between stable valley airmasses and fog events is statistically significant and that the presence of such airmasses makes the formation of fog more likely in mid-winter.