Preprints
https://doi.org/10.5194/egusphere-2025-2427
https://doi.org/10.5194/egusphere-2025-2427
18 Jul 2025
 | 18 Jul 2025

Interdecadal rainfall cycles in spatially coherent global regions and their interaction with climate modes

Tobias Frederick Selkirk, Andrew W. Western, and J. Angus Webb

Abstract. Interdecadal cycles in rainfall influence long-term hydrological variability, affecting water resource management, agriculture, and flood or drought preparedness across the globe. Previous studies have found evidence of cycles over limited regions but the global distribution and interaction with major climate modes remain unclear. Using the global GPCC v2022 2.5° gridded dataset (1891–2020), we applied a Gaussian mixture model to detect significant clustering of cycles in rainfall, derived from wavelet analysis of individual grid points. Three Global Rainfall Cycles (GRCs) emerged at 12.9-, 19.9-, and 28.2-years, were widespread, and aligned in length and phase to previous research. Two longer cycles (35.9- and 45.9-years) were also significant but interpreted cautiously due to their period relative to the dataset’s length. The 12.9- and 19.9-year GRCs showed strong phase coherence and spatial overlap with the El Niño-Southern Oscillation and Interdecadal Pacific Oscillation climate modes, but not with the Indian Ocean Dipole or North Atlantic Oscillation. Notably, GRCs explained more rainfall variance than expected from the effect of these climate modes alone, suggesting another driver may influence rainfall directly and via climate interactions. These findings are of significance to global water management and rainfall modelling, offering the potential to enhance flood and drought forecasting in strongly affected regions.

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Tobias Frederick Selkirk, Andrew W. Western, and J. Angus Webb

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-2427', Anonymous Referee #1, 19 Aug 2025
    • RC2: 'Reply on RC1', Anonymous Referee #2, 22 Aug 2025
      • RC4: 'Reply on RC2', Anonymous Referee #2, 22 Aug 2025
        • AC4: 'Reply on RC4', Tobias Selkirk, 11 Sep 2025
      • AC3: 'Reply on RC2', Tobias Selkirk, 11 Sep 2025
    • AC1: 'Reply on RC1', Tobias Selkirk, 11 Sep 2025
  • RC3: 'Comment on egusphere-2025-2427', Anonymous Referee #2, 22 Aug 2025
    • AC2: 'Reply on RC3', Tobias Selkirk, 11 Sep 2025

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-2427', Anonymous Referee #1, 19 Aug 2025
    • RC2: 'Reply on RC1', Anonymous Referee #2, 22 Aug 2025
      • RC4: 'Reply on RC2', Anonymous Referee #2, 22 Aug 2025
        • AC4: 'Reply on RC4', Tobias Selkirk, 11 Sep 2025
      • AC3: 'Reply on RC2', Tobias Selkirk, 11 Sep 2025
    • AC1: 'Reply on RC1', Tobias Selkirk, 11 Sep 2025
  • RC3: 'Comment on egusphere-2025-2427', Anonymous Referee #2, 22 Aug 2025
    • AC2: 'Reply on RC3', Tobias Selkirk, 11 Sep 2025
Tobias Frederick Selkirk, Andrew W. Western, and J. Angus Webb
Tobias Frederick Selkirk, Andrew W. Western, and J. Angus Webb

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Short summary
This study finds three cycles in yearly rainfall worldwide of approximately 13, 20 and 28 years. The cycles rise and fall together across continents and also appear in the El Niño–Southern Oscillation (ENSO), a major climate driver of rain. However the signal in ENSO is too small to explain the strong local influence, the results point to another, still-unknown force that may shape both ENSO and global rainfall.
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