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<p>The profound impacts of North American (NA) precipitation variability on drought, agriculture, and society make understanding its external and internal drivers critically important. However, most studies have focused on either external forcing or internal variability in specific NA regions, neglecting their combined effects across the entire continent. Here, we combine long-term observational data and CMIP6 simulations to find the distinct roles of anthropogenic forcing and low-frequency internal variability. Results reveal a long-term wetting trend primarily driven by greenhouse gas forcing, though systematically underestimated by models. Decadal precipitation oscillations are modulated by internal variability, especially the Interdecadal Pacific Oscillation (IPO), whose sea surface temperature anomalies trigger Rossby waves that alter moisture transport and establish a tripolar precipitation pattern. This pattern dominates NA precipitation variability at decadal scales, surpassing anthropogenic influences. From 2021 to 2050, the tripolar pattern is projected to persist, contingent on IPO phase. By 2100, constrained projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest a further intensification of precipitation increases. This study shows how NA rainfall responds differently to human influence and natural oscillations over decades, with implications for improving our ability to predict and attribute regional climate changes.</p>

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External and internal controls on decadal precipitation variability over North America

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Xiaolu Fan,
  • Jianping Huang,
  • Yongkun Xie,
  • Wenmin Wei,
  • Yu Ren,
  • Yihui Xu,
  • Ming Peng,
  • Li Fu

摘要

The profound impacts of North American (NA) precipitation variability on drought, agriculture, and society make understanding its external and internal drivers critically important. However, most studies have focused on either external forcing or internal variability in specific NA regions, neglecting their combined effects across the entire continent. Here, we combine long-term observational data and CMIP6 simulations to find the distinct roles of anthropogenic forcing and low-frequency internal variability. Results reveal a long-term wetting trend primarily driven by greenhouse gas forcing, though systematically underestimated by models. Decadal precipitation oscillations are modulated by internal variability, especially the Interdecadal Pacific Oscillation (IPO), whose sea surface temperature anomalies trigger Rossby waves that alter moisture transport and establish a tripolar precipitation pattern. This pattern dominates NA precipitation variability at decadal scales, surpassing anthropogenic influences. From 2021 to 2050, the tripolar pattern is projected to persist, contingent on IPO phase. By 2100, constrained projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest a further intensification of precipitation increases. This study shows how NA rainfall responds differently to human influence and natural oscillations over decades, with implications for improving our ability to predict and attribute regional climate changes.