Professor Seung-Ki Min and Dr. Minkyu Lee, from the Division of Environmental Science and Engineering at Pohang University of Science and Technology (POSTECH), have used a high-resolution climate model to conduct a pioneering quantitative analysis of the impact of global warming on typhoons making landfall on the Korean Peninsula. This research has been recently published in npj Climate and Atmospheric Science.

Notably, global warming is giving way to a surge in more powerful typhoons which maintain its intensity longer and thereby cause stronger damage. Accurate typhoon prediction and damage reduction necessitate better understanding of the global warming influences, for which climate model simulations with a km-scale resolution are eccential. However, studies quantifying the anthropogenic warming contribution to typhoons affecting Korea, especially research into the rainfall extremes accompanying typhoons, remain scant.

To overcome this, the research team designed a 3 km high-resolution regional climate model simulation to investigate the impact of global warming on typhoon intensity and extreme precipitation. Four extremely strong typhoons that made landfall on the Korean Peninsula between 2011 and 2020 were chosen for simulation under current climate condition and counterfactual condition without human-induced warming. To reduce the uncertainties in regional sea surface temperature changes due to global warming, they utilized diverse ocean warming patterns estimated from CMIP6multiple climate models.

The findings show that accounting for global warming from human activities augmented overall typhoon intensity and precipitation. The research team observed that the impact of warming was pronounced more strongly at maximum typhoon intensity than the average intensity. This implies more frequent occurrences of powerful super typhoons over East Asia in the future. Additionally, the area exposed to extreme rainfall generated by typhoons expanded 16 to 37 percent due to warmer climate conditions. Further, the expansion of extreme precipitation area is attributed to the strengthening of upward motion near the typhoon center and the increase in atmospheric water vapor due to the ocean surface warming.

Professor Min explained, “Our results from high-resolution climate model simulations provide conclusive evidence that global warming has amplified the strength of recent typhoons making landfall on the Korean Peninsula. Continued escalation of global warming could lead to stronger typhoons and more extensive occurrences of rainfall extremes, demanding heightened sector-specific preparedness measures.”

This study received support from the Mid-Career Researcher Program of the National Research Foundation of Korea and the Korea Meteorological Administration Research and Development Program on Climate and Climate Change Monitoring and Prediction Information Application Technology.

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.

Also working on the project, funded by a $1.17 million grant from the National Science Foundation, were several other members of the U Department of Atmospheric Sciences, including Gannet Hallar and Sebastian Hoch, along with Eric Pardyjak of the Department of Mechanical Engineering, a group of scientists from the National Center for Atmospheric Research (NCAR), and Dr. Ismail Gultepe from Ontario Tech University, Canada.

Because it reduces visibility, fog poses serious hazards to the traveling public. For example, fog is the second leading cause of aircraft accidents after high winds. It leads to automobile crashes and disrupts ferry operations.

Between 1995 and 2004 in the United States, 13,720 have died in fog-related accidents.

Improving fog forecasting would make traveling more safe, Pu said.

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.

The ground is cooling overnight while denser, cooler air drops from mountain tops collecting in the valleys, in a phenomenon known as “cold air drainage.” Cooled by the ground, the dropping air temperature can approach the dew point, and if there is sufficient moisture in the air, fog begins to form, becoming the most dense around sunrise when surface temperatures are lowest.

Winter nights create favorable conditions for different forms of fog, such as cold-air pool fog, ephemeral mountain valley fog and radiative ice fog.

The Heber Valley project homed in on cold-air fog which forms in freezing temperatures below zero degrees Celsius, according to Pu. However by observing how these varying kinds of fog form and dissipate, the researchers are continuing to learn about the meteorological conditions and physical processes governing the formation of fog.

For the CFACT study, the NCAR and U team set up two major data-collecting stations, one near Deer Creek Reservoir and another a few miles up the Provo River. These are low spots in the valley, about 5,450 feet above sea level, that see the densest fog. These sites were equipped with 100-foot towers to support an array of instruments that captured various meteorological data associated with humidity, wind, visibility, temperature, even snow depths, and soil moisture. The recordings were made from both in situ and remote-sensing platforms.

Additionally, the team recorded a lesser array of data points at nine satellite sites.

During the seven-week CFACT field campaign, nine intensive observation periods (IOPs), each conducted over 24-hour periods, yielded a dataset that included high-frequency radiosonde profiles, tethered balloon profiles, remotely sensed thermodynamic and wind profiles, surface meteorological observations and microphysical and aerosol measurements.

Besides fog IOPs, the variety of non-fog IOPs provided valuable observations for understanding near-surface inversion, ice crystal formation, moisture advection and transportation, and stable boundary layers over complex terrain, all of which are essential factors related to fog formation. Comprehensive studies are ongoing for an improved understanding of cold fog over complex terrain.

The study appeared Nov. 15 in the Bulletin of the American Meteorological Society. U researchers involved with the study included Zhaoxia Pu, Sebastian Hoch, A. Gannet Hallar, Rebecca Beal, Geraldo Carrillo-Cardenas, Xin Li and Maria Garcia of the Department of Atmospheric Sciences and Eric Pardyjak and Alexei Perelet of the Department of Mechanical Engineering.

While accelerating sea level rise will result in widespread intermittent flooding and long-term inundation in many coastal communities, the paper, recently published in Nature Communications, showed that when these levels increase above 4 feet, minority populations will be disproportionately at risk of isolation.

Rising sea levels could lead to isolation by disrupting transportation networks and roads, meaning that those affected lose access to essential locations such as critical emergency services and schools.

The study further exposed that renters and older adults face a greater risk of isolation, highlighting the growing connection between historical drivers of existing social inequality and the groups that incur the most risk of climate change.

According to Kelsea Best, lead author of the study and an assistant professor of civil, environmental and geodetic engineering at The Ohio State University, the first step in better characterizing these threats is changing how researchers assess community risk, as most studies measure this by exclusively determining impacts via direct flooding. But concentrating on this sole measurement neglects more complex aftereffects of sea level rise, such as isolation, and reinforces inequality in coastal areas, Best said.

“We need to re-conceptualize how we measure who is burdened by sea level rise because there are so many ways that people might be burdened before their home is flooded,” she said.

Current reports estimate that around 20 million coastal residents in the U.S. will be affected by rising sea levels by 2030, but the paper notes that this number doesn’t include the whole impact global warming will have on certain communities and demographics.

Notably, because people need access to essential places like grocery stores, public schools, hospitals and fire stations, Best and her colleagues argue that an inability to reach these places impacts individuals just as negatively as if they were living in inundated homes themselves, and should be documented as such.

Most importantly, their results expose one of the main reasons for these vast differences in risk: A group’s risk of isolation is intimately entwined with specific road networks and where vital services are located in relation to where affected individuals reside.

They identified these disparities in risk by overlaying OpenStreetMap (OSM) road network data with National Oceanographic and Atmospheric Administration (NOAA) mean higher high water (MHHW) scenarios. These projections were then combined with recent census data to estimate the percentage of a population that would be left out or missed in estimates of who would be impacted by sea level rise if researchers only counted those who suffered direct inundation.

“If we take a one-size-fits-all approach, or a seemingly ‘neutral’ approach to understanding who gets access to safe, affordable housing and community in a world with climate change, then we’re really just exacerbating these inequities and it’s not good enough,” said Best. “We have to deliberately seek to provide access to adaptation resources to groups of people who have historically been left out and therefore have fewer resources to respond in the first place.”

The researchers showed that Hispanic populations are often overrepresented in the total citizenry for being at risk of isolation beginning at 4 feet of sea level rise, and Black populations are overrepresented after 6 feet. Alternatively, white populations are underrepresented after 5 feet of sea level rise.

But to determine when these disparities will begin to develop, Best’s team compared two long-term sea level rise scenarios: an intermediate scenario in which global sea level rise increased by a meter by 2100, and a high scenario in which that number increased to 2 meters by the same year.

Alarmingly, the study found strong evidence that these isolation effects would set in by 2120 in the intermediate scenario and as early as 2090 in the high scenario. “This timeline matters from a planning and adaptation perspective,” said Best. “Part of why we included the temporal piece is to say this issue would not be as much of a problem if we had urgent, aggressive mitigation.

“The effects of climate change are going to be further reaching and more cascading than might be directly obvious, and those effects are not going to be felt equitably,” said Best. “So we need to be thinking about those populations most at risk from the beginning and develop policies to support them.”

The work was supported by the Clark Distinguished Chair Endowment (given to study co-author Deb. A. Neimeier of the University of Maryland) and the National Science Foundation. Other co-authors were Qian He from Rowan University, Allison C. Reilly from the University of Maryland, and Mitchell Anderson and Tom Logan from the University of Canterbury.