Scientists are unraveling the mysteries of fog formation

Although fog is a common weather phenomenon, it is also quite mysterious. Fog has long been a subject of intrigue and concern, particularly in areas of complex terrain like mountainous regions. 

It is a major hazard to transportation, yet meteorologists struggle to predict fog formation with the accuracy they’ve achieved for other weather events. 

A recent study from the University of Utah, led by Professor Zhaoxia Pu, is shedding new light on this issue. This research, part of the Cold Fog Amongst Complex Terrain (CFACT) project, aims to deepen our understanding of fog formation, with the goal of improving forecasting methods.

The challenge of predicting fog

Fog forms close to the ground, influenced by air temperature, humidity, and the terrain itself. Yet, its prediction remains a challenge. 

The physical processes that result in fog are complex, making it harder to forecast than precipitation, wind, and other stormy events.

“Our understanding is limited. In order to accurately forecast fog we should better understand the process that controls fog formation,” said Professor Pu.

The CFACT project

The CFACT project, funded by a $1.17 million grant from the National Science Foundation, involves a team from the University of Utah’s Department of Atmospheric Sciences, including Gannet Hallar and Sebastian Hoch, Eric Pardyjak from the Department of Mechanical Engineering, scientists from the National Center for Atmospheric Research (NCAR), and Dr. Ismail Gultepe from Ontario Tech University, Canada. 

The project’s primary objective is to investigate the life cycle of cold fog in mountain valleys, particularly in the Heber Valley, located about 50 miles southeast of Salt Lake City.

The dangers of fog

Improving fog forecasting is particularly important for public safety. Fog significantly reduces visibility, posing dangers to all forms of transportation.

It is the second leading cause of aircraft accidents after high winds and is responsible for numerous automobile crashes and disruptions in ferry operations. Between 1995 and 2004, fog-related accidents in the United States resulted in 13,720 deaths.

How the research was conducted

The researchers used the Numerical Weather Prediction (NWP) model, which processes meteorological observations for weather predictions.

“Fog involves a lot of physics processes so it requires a computer model that can better represent all these processes,” explained Professor Pu. 

“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.”

The Heber Valley 

The Heber Valley, with its typical mountain valley topography, served as the ideal location for this research. Over seven weeks in the winter of 2022, the team collected data from two major stations equipped with 100-foot towers and various instruments. 

These stations, located near Deer Creek Reservoir and along the Provo River, gathered data on humidity, wind, visibility, temperature, snow depths, and soil moisture. Multiple satellite sites also contributed to the data collection.

Intensive observation periods 

The team conducted nine intensive observation periods (IOPs) over 24-hour periods. These IOPs included high-frequency radiosonde profiles, tethered balloon profiles, remotely sensed thermodynamic and wind profiles, surface meteorological observations, and microphysical and aerosol measurements. 

The variety of non-fog IOPs provided insights into near-surface inversion, ice crystal formation, moisture advection and transportation, and stable boundary layers over complex terrain.

Study implications 

This comprehensive study is ongoing, but it has already begun to unravel the complexities of fog formation in mountain valleys. By understanding the meteorological conditions and physical processes involved, the researchers hope to improve fog prediction models. 

Such advancements would not only contribute to scientific knowledge but also significantly enhance public safety by reducing the risks associated with this elusive weather phenomenon.

More about the dangers of fog

Fog, although a natural and often visually striking phenomenon, poses several significant dangers, particularly in the context of transportation and outdoor activities. Here are some of the key risks associated with fog:

Reduced visibility

The most immediate danger of fog is the significant reduction in visibility. This can be especially hazardous for drivers, pilots, and mariners, as it becomes difficult to see other vehicles, obstacles, or navigational markers. Reduced visibility increases the risk of accidents and collisions.

Transportation accidents

Due to decreased visibility, fog is a major factor in transportation accidents. It can lead to multi-vehicle pile-ups on roads and highways. 

In aviation, fog can disrupt airport operations, leading to flight delays, diversions, or accidents during takeoff and landing. In maritime contexts, fog can cause collisions between ships or with shore installations.

Disorientation and confusion

In outdoor settings, especially in unfamiliar terrain, fog can cause disorientation. Hikers, for instance, might lose their sense of direction.

Health issues

Fog may exacerbate health issues, especially in urban areas where it traps pollutants and reduces air quality. This is particularly risky for individuals with respiratory conditions like asthma or chronic bronchitis.

Economic impact

Dense fog may have a significant economic impact due to delayed transportation services. It can disrupt supply chains, lead to flight and shipping cancellations or delays, and affect businesses dependent on timely transportation.

Agricultural impact

In some cases, fog impacts agriculture. Persistent fog can deprive plants of sunlight, affecting their growth. It can also contribute to the spread of fungal diseases in certain crops.

The study is published in the journal Bulletin of the American Meteorological Society. 

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