You might not initially think of fog as a form of severe weather, but when fog sets in and visibility plummets, transportation becomes dangerous. It’s the second-most-likely cause of aircraft accidents after strong winds, but despite the high impact of fog events and a long history of fog research, fog prediction remains a long-standing challenge for weather prediction because of complex interactions among the land surface, water, and atmosphere. There’s still a lot of fundamental things about fog that we don’t know.

University of Utah mechanical engineering professor Eric Pardyjak (pictured) and U atmospheric sciences professor Zhaoxia Pu are hoping to change that through a large-scale observational experiment using Utah’s Heber Valley as the laboratory. For about six weeks, beginning in January 2022, Pu, Pardyjak and their colleagues, including scientists from Environment and Climate Change Canada, will watch a network of sensors on the ground in the Heber Valley along with satellite observations and data from the National Center for Atmospheric Research. The valley is bounded by mountains, relatively flat in the basin and features two lakes-Jordanelle and Deer Creek reservoirs. Its conditions, Pu says, are representative of mountain valleys around the world.

On winter nights, cold air pools in the valley floor and creates favorable conditions for several forms of fog, including cold-air pool fog, mountain valley cold fog and radiative ice fog. By observing how these different kinds of fog form and dissipate, the researchers hope to learn about the physical processes governing the existence of fog and improve fog prediction. The study is funded by a $1.17 million grant from the National Science Foundation.