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taylorvich [soylentnews.org] writes:

https://phys.org/news/2023-12-fog-mountainous-areas.html [phys.org]

Of the world's various weather phenomena, fog is perhaps the most mysterious, forming and dissipating near the ground with fluctuations in air temperature and humidity interacting with the terrain itself.

While fog presents a major hazard to transportation safety, meteorologists have yet to figure out how to forecast it with the precision they have achieved for precipitation, wind and other stormy events.

This is because the physical processes resulting in fog formation are extremely complex, according to Zhaoxia Pu, a professor of atmospheric sciences at the University of Utah.

"Our understanding is limited. In order to accurately forecast fog we should better understand the process that controls fog formation," said Pu, who led a fog study focusing on a northern Utah valley.

Now, in a recent paper published by the American Meteorological Society, Pu and her colleagues have reported their findings from the Cold Fog Amongst Complex Terrain (CFACT) project, conceived to investigate the life cycle of cold fog in mountain valleys.
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Today, most forecasting uses a computer model known as Numerical Weather Prediction (NWP), which processes massive meteorological observations with computer models to output predictions for precipitation, temperature, and all sorts of other elements of the weather. However the current computer model doesn't work well for fog, and Pu's team hopes that improvements can be made using the masses of data they gathered over seven weeks in the winter of 2022 at several sites in the Heber Valley.

"Fog involves a lot of physics processes so it requires a computer model that can better represent all these processes," Pu said. "Because fog is clouds near the ground, it requires a high-resolution model to resolve it, so we need models at a very fine scale, which are computationally very expensive. The current models (relatively coarser in resolution) are not capable of resolving the fog processes, and we need to improve the models for better fog prediction."

Located bout 50 miles southeast of Salt Lake City, Heber Valley is nestled behind the Wasatch Mountains and framed by two major reservoirs on the Provo River.

This scenic basin is a typical mountain valley, hemmed by Mt. Timpanogos and other high peaks, with the reservoirs serving as a moisture source. The seven-week study window covered the time of year when Heber Valley is the foggiest.

Valley fog is a perfect example of how topography and atmospheric processes converge to create a distinctive weather phenomenon.
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