Dr. Xueke Li is a Research Associate at the University of Pennsylvania. Her research aims to advance the physical understanding of climate variability and extremes, and their impacts and associated risks for the environment and society, by harnessing multi-source datasets, remote sensing, geographic information systems (GIS), machine learning, and computational Earth system modeling. Her areas of focus span from densely populated regions affected by mid-latitude weather extremes to remote polar environments undergoing rapid sea ice loss. Her research at the intersections of the atmosphere, hydrosphere, cryosphere, and land surface has also led to her role as an Associate Editor of Physics and Chemistry of the Earth, Parts A/B/C, and as an Editorial Board Member of Scientific Reports.

Prior to joining Penn, Dr. Li was a Postdoctoral Research Associate at Brown University. She earned her Ph.D. in Geography from the University of Connecticut. For more on her research, see the Research and Publications tabs.

Research Highlights

Planetary waves linked to summer extreme weather events have tripled since 1950

This is the first study to show a statistically significant increase in the frequency of planetary wave resonance events in the Northern Hemisphere that can be tied to the overall warming of the planet. We found that the average number of resonance events per year has tripled since the advent of adequate upper atmospheric measurements in the mid-20th century, rising from roughly 1 event per year in 1950 to about 3 per year now, a rate of increase that closely parallels the increase in heatwave occurrences across the United States.

PNAS article

The strongest nor’easters are becoming stronger

In this collaborative study, we tracked 900 nor’easters—named for the unusual northeasterly direction of their strongest winds along the U.S. East Coast—back to 1940, using a cyclone tracking approach combined with long-term reanalysis of historical climate conditions. The findings show that today’s strongest nor’easters are already significantly windier and wetter than those of the mid-20th century. In the most powerful storms, wind speeds have increased by about 5.4 percent, translating to roughly a 17 percent increase in destructive potential—offering new insight into how nor’easters along the Atlantic coast are responding to a warming climate.

PNAS article

Planetary wave and land-atmosphere interactions fueled the deadly 2021 Pacific Northwest heatwave

From late June to mid-July 2021, the Pacific Northwest was scorched under an unprecedented "heat dome," shattering long-standing temperature records. Cities like Portland and Seattle—better known for their mild summers—grappled with triple-digit heat. Our research shows that unusual summer jet stream behavior, which is more likely under human-caused warming yet remains poorly captured by current climate models, played a central role in fueling this event. In the weeks leading up to the heat dome, the planetary wave amplified through resonance, which likely dried out soils across the region, reducing their ability to cool the surface. That soil moisture loss, in turn, fed back into the atmosphere, intensifying surface heating and helping drive the extreme temperatures observed during the event.

PNAS article

Credit: Kristjan Fridriksson

Arctic warming opens door to new trade routes by midcentury

The Arctic remains one of the world's least explored and last wild frontiers. Yet our collaborative research shows that regions of the Arctic Ocean once locked in ice year-round are warming so rapidly that, within just two decades, they may be ice-free for months on end. Such dramatic changes could transform global trade. By midcentury, new shipping lanes—likely to emerge under all but the most aggressive emissions control scenarios—could open across international waters. These routes would not only reduce the shipping industry's carbon footprint but also weaken Russia's control over Arctic trade.

PNAS article

Credit: Jared McGhie, Australian Antarctic Division

Record low Antarctic sea ice raises risks for supply chains

As part of this multi-institutional study, we show that the recent record lows in Antarctic sea ice have seen more icebergs calving from the continent's ice shelves—a process that could accelerate global sea level rise beyond what current models project. The retreat of summer sea ice will also narrow the window during which Antarctic research bases can be resupplied over the ice, increasing both logistical challenges and safety risks for vessels stationed during supply missions.

PNAS Nexus article

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