Supercooled clouds over the highest mountains respond differently to climate change
Most studies of how clouds are responding to climate change focus on clouds over the oceans, rather than over mountains. Those that do focus on mountain clouds tend to explore cloud microphysics rather than long-term trends in cloud phase. But understanding cloud behavior over regions such as the Tibetan Plateau, which supplies water to hundreds of millions of people, is critical—especially as…
Studies of how clouds respond to climate change overwhelmingly focus on oceanic regions, overlooking critical mountainous areas. The Tibetan Plateau, which supplies water to over 700 million people, is one such region whose cloud behavior is vital to understand, particularly as diminishing snowpack and altered precipitation patterns threaten this crucial water source.
Zhang and colleagues bridge this knowledge gap by analyzing long-term changes in cloud phases over global mountain ranges, including the Tibetan Plateau, European Alps, Andes, Appalachians, and Rockies. Utilizing satellite observations and climate data from 2003 to 2022, they examined cloud fraction, cloud top temperature, and cloud height across these regions and their adjacent lowlands.
Their findings, published in AGU Advances, reveal that most mountainous regions experienced an increase in warm-liquid and ice cloud phases, accompanied by reduced vertical development and fewer supercooled clouds. Ice cloud tops over mountains rose and cooled at 2-4 times the rate of clouds over surrounding lowlands. However, supercooled clouds exhibited varied responses to warming, depending on their elevation.
Over lowlands and lower-elevation mountains, supercooled cloud tops warmed and descended, indicating suppressed vertical cloud structure development. Conversely, over the highest-elevation mountains like the Tibetan Plateau and the Andes, supercooled clouds not only cooled but also ascended further. This difference in response could be linked to stronger warming at lower altitudes destabilizing the vertical thermal profile of the Tibetan Plateau, allowing clouds to reach colder air layers.
Meanwhile, colder and higher clouds over the Andes were associated with increased atmospheric moisture content. The study concludes that high-elevation clouds are responding more strongly and differently to warming compared to clouds in other regions. Further research is needed to understand how changes in icy high-elevation clouds over the Tibetan Plateau and the Andes might affect Earth's radiative energy balance, either by trapping heat or reflecting it back into space. This could significantly impact regional radiative energy budgets and inform climate models.
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