Central Asia is characterized by a predominantly arid to semi-arid climate. Water availability in this region is limited and controlled by precipitation, particularly during winter. The precipitation is highly variable from year to year, making the regional water cycle especially sensitive to changes in the climate system.

For decades, year-to-year changes in Central Asian precipitation has been largely attributed to tropical climate variability by research, especially the El Niño-Southern Oscillation (ENSO). However, observations have long suggested that ENSO alone cannot fully explain the variability, particularly during years with pronounced anomalies. This suggests that there may be the influence of other climate drivers.

In a study published in npj Climate and Atmospheric Science, the researchers from the Institute of Atmospheric Physics of the Chinese Academy of Sciences, the University of Sheffield and the University of Exeter, revealed that changes in Antarctic ozone during boreal autumn significantly influence winter precipitation in Central Asia.

"Antarctic ozone has long been recognized as a key signal of human influence on the climate system," said HUANG Gang, one of the corresponding authors of this study. "What we show here is that its variability is not only important locally, but can also affect hydroclimate in distant regions, including Central Asia."

Based on multiple lines of evidence including observational datasets, reanalysis products, and climate model experiments, the researchers identified a robust statistical relationship between autumn Antarctic ozone and subsequent winter precipitation in Central Asia. This relationship is largely independent of ENSO, suggesting that Antarctic ozone provides an additional and complementary source of predictability.

The researchers revealed the physical mechanisms for this connection. In the stratosphere, higher Antarctic ozone levels lead to warming over the polar region, which weakens the polar vortex and reduces the strength of high-latitude westerly winds. This signal propagates downward into the troposphere over weeks to months, shifting the Southern Annular Mode into its negative phase. As a result, large-scale circulation patterns adjust, with westerly jets moving equatorward and pressure patterns reorganizing across the Southern Hemisphere.

These changes trigger a reconfiguration of the meridional circulation. Enhanced upward motion in the Southern Hemisphere mid-latitudes and associated cross-equatorial energy transport influence the Northern Hemisphere Hadley circulation, shifting mid-latitude atmospheric circulation southward. This leads to increased low-level moisture convergence and stronger upward motion over Central Asia, both of which favour enhanced winter precipitation.

Besides this atmospheric pathway, Antarctic ozone variability also influences ocean-atmosphere interactions. Changes in surface winds associated with the Southern Annular Mode modify ocean circulation through Ekman transport, creating a dipole pattern of sea surface temperature anomalies in the Southern Ocean. This pattern can persist and extend toward lower latitudes, eventually exciting Rossby wave trains that propagate across hemispheres. These waves alter tropical circulation, promote warming in the central-eastern Pacific, and weaken zonal atmospheric circulation along the equator. The resulting shift in tropical convection enhances upper-level divergence over Central Asia, reinforcing precipitation anomalies.

"Taken together, these processes show that how a signal originating in the Antarctic stratosphere can cascade through the climate system and influence rainfall thousands of kilometres away, which highlights the importance of considering cross-hemispheric linkages when we study regional climate variability," said TANG Haosu, another corresponding author of this study.

Moreover, the researchers developed a statistical prediction model that combines Antarctic ozone and ENSO as joint predictors of Central Asian winter precipitation. They showed that compared to using ENSO alone, including ozone variability significantly improves predictive skill. They suggested that combining Antarctic ozone variability and ENSO may amplify precipitation-related risks in Central Asia under a changing climate, as including ozone effects points to greater potential impacts on population exposure and economic activity.

This work provides new evidence that the Antarctic is not only a region strongly affected by climate change, but also an active driver of climate variability at lower latitudes. By linking stratospheric processes to regional hydroclimate, it advances the understanding of how different components of the Earth system interact across vast distances.

As climate variability continues to evolve, identifying new sources of predictability will be essential for improving water resource management and climate adaptation in vulnerable regions. The authors suggest that incorporating high-latitude signals such as Antarctic ozone into forecasting systems could help provide more reliable and actionable information for decision-makers in Central Asia and beyond.