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<p>This study investigated interdecadal and multidecadal variations in summer (June–August) precipitation in Siberia during 1901–2020 to clarify how low-frequency variability contributes to long-term precipitation changes. Two dominant timescales were identified: a 20–40-year interdecadal mode and a 45–90-year multidecadal mode. The 20–40-year mode is characterized by a north–south dipole pattern in the atmospheric circulation over Siberia and from Mongolia to Northeast China, producing persistent wet and dry periods over eastern Siberia. Cyclonic circulation over Siberia and anticyclonic circulation over Northeast China enhance westerly moisture transport to Siberia during wet periods. This circulation pattern strengthens cyclogenesis by increasing atmospheric baroclinicity along the Polar Frontal Zone. The 45–90-year variation modulates the background moisture flux over central Siberia. It shifted to a positive phase in the late 1990s, which enhanced westerly moisture transport over southern central and eastern Siberia. The wet phase of the 20–40-year mode in the 2000s was intensified by its combination with the 45–90-year mode. These interactions explain the observed increase in Siberian summer precipitation since the early 1980s as a synergistic effect of two low-frequency variations. The upper-tropospheric wave trains associated with the 20–40-year and 45–90-year modes correspond broadly to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), respectively. Furthermore, the reduction in Arctic sea ice under global warming has likely strengthened the atmospheric circulation associated with the interdecadal mode. The spatial pattern of sea level pressure anomalies in the Arctic, characterized by lower pressure over the Eurasian side and higher pressure over the North American side, resembles that related to the 20–40-year precipitation variability. These results suggest that the recent increase in Siberian precipitation may reflect the combined influence of low-frequency variability associated with the PDO and AMO, together with the reduction in Arctic sea ice within the context of global warming. </p>

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Interdecadal and multidecadal variabilities in summer precipitation affecting persistent wet and dry years over Siberia

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  • 发表日期：

    2026年7月9日

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  • Hironari Kanamori,
  • Yoshiki Fukutomi,
  • Hatsuki Fujinami,
  • Tetsuya Hiyama

摘要

This study investigated interdecadal and multidecadal variations in summer (June–August) precipitation in Siberia during 1901–2020 to clarify how low-frequency variability contributes to long-term precipitation changes. Two dominant timescales were identified: a 20–40-year interdecadal mode and a 45–90-year multidecadal mode. The 20–40-year mode is characterized by a north–south dipole pattern in the atmospheric circulation over Siberia and from Mongolia to Northeast China, producing persistent wet and dry periods over eastern Siberia. Cyclonic circulation over Siberia and anticyclonic circulation over Northeast China enhance westerly moisture transport to Siberia during wet periods. This circulation pattern strengthens cyclogenesis by increasing atmospheric baroclinicity along the Polar Frontal Zone. The 45–90-year variation modulates the background moisture flux over central Siberia. It shifted to a positive phase in the late 1990s, which enhanced westerly moisture transport over southern central and eastern Siberia. The wet phase of the 20–40-year mode in the 2000s was intensified by its combination with the 45–90-year mode. These interactions explain the observed increase in Siberian summer precipitation since the early 1980s as a synergistic effect of two low-frequency variations. The upper-tropospheric wave trains associated with the 20–40-year and 45–90-year modes correspond broadly to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), respectively. Furthermore, the reduction in Arctic sea ice under global warming has likely strengthened the atmospheric circulation associated with the interdecadal mode. The spatial pattern of sea level pressure anomalies in the Arctic, characterized by lower pressure over the Eurasian side and higher pressure over the North American side, resembles that related to the 20–40-year precipitation variability. These results suggest that the recent increase in Siberian precipitation may reflect the combined influence of low-frequency variability associated with the PDO and AMO, together with the reduction in Arctic sea ice within the context of global warming.