Zhou et al. (2026) Multi-timescale characteristics and possible causes of summer precipitation duration in Southwest China

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-01-09
• Authors: Jie Zhou, Junhu Zhao, Yonghua Li, Hongyv Tang, Guolin FENG
• DOI: 10.1007/s00704-025-06014-9

Research Groups

• Geleshan National Climate Observatory, CMA Key Open Laboratory of Transforming Climate Resources to Economy, Chongqing Climate Center, Chongqing, China
• CMA Key Laboratory for Climate Prediction Studies, National Climate Center, Beijing, China
• School of Physical Science and Technology, Yangzhou University, Yangzhou, China

Short Summary

This study investigates the multi-timescale variability of summer precipitation duration in Southwest China, focusing on the Yunnan-Guizhou Plateau (YGP) from 1981–2023. It reveals a significant decreasing trend in precipitation duration and attributes inter-decadal variations to the Pacific Decadal Oscillation (PDO) and inter-annual variations to equatorial western Indian Ocean sea surface temperature anomalies (SSTA).

Objective

• To analyze the multi-timescale variability (long-term trend, inter-annual, and inter-decadal) of summer precipitation duration and non-precipitation duration in Southwest China.
• To investigate the associated large-scale atmospheric circulation patterns and their relationship with sea surface temperature anomalies (SSTA) that influence these variations, particularly over the Yunnan-Guizhou Plateau (YGP).

Study Configuration

• Spatial Scale: Southwest China, including the Sichuan Basin, Yunnan-Guizhou Plateau (YGP), and Western Sichuan Plateau. Detailed analysis focuses on the YGP.
• Temporal Scale: Summer months (June to August) from 1981 to 2023 (43 years). Analysis covers long-term trends, inter-annual, and inter-decadal variations.

Methodology and Data

• Models used:
  • 9-year Gaussian filter (for separating inter-annual and inter-decadal components)
  • Regime Shift Index (RSI; Rodionov 2004) based on a sequential t-test
  • Composite analysis of atmospheric circulation patterns
  • Correlation analysis (with SSTA, PDO index, Bay of Bengal Anticyclone intensity index, Bay of Bengal westerly index, Equatorial Western Indian Ocean SSTA Index, Niño3.4 Index)
  • Power spectra analysis
  • T-test for statistical significance (0.05 and 0.02 levels)
• Data sources:
  • Daily precipitation data from 391 meteorological stations in Southwest China (China Surface Daily Data, National Meteorological Information Center of CMA).
  • ERA-5 monthly reanalysis data (ECMWF) for U winds, V winds, geopotential height, specific humidity, and sea level pressure (0.25° × 0.25° horizontal resolution, 23 vertical layers).

Main Results

• Over 1981–2023, Southwest China experienced a weakening trend in summer precipitation duration, characterized by reduced total precipitation days, shortened mean duration of wet spells, and prolonged mean duration of dry spells.
• The Yunnan-Guizhou Plateau (YGP) exhibited the most pronounced and statistically significant (p < 0.02) shortening trend in summer precipitation duration, with decadal averages decreasing from 2.47 days (1980s) and 2.65 days (1990s) to 2.38 days (2001-2010) and 2.34 days (2011-2023).
• Summer precipitation duration over the YGP showed distinct inter-annual (2.3–2.5-year cycle) and inter-decadal (28-year cycle) oscillations, with a regime shift to shorter durations and increased inter-annual variability occurring around 2002/2003.
• Inter-decadal scale: The positive phase of the Pacific Decadal Oscillation (PDO) favors an anomalous anticyclonic circulation over the Bay of Bengal at 700 hPa. This circulation enhances water vapor transport from the Bay of Bengal to the YGP, leading to longer summer precipitation durations.
• Inter-annual scale: Anomalous warming of Sea Surface Temperature (SST) in the equatorial western Indian Ocean intensifies westerly anomalies over the northern Bay of Bengal. This facilitates water vapor transport from the Indian Ocean to the YGP, causing longer summer precipitation durations.

Contributions

• Provides a comprehensive analysis of multi-timescale (long-term, inter-annual, inter-decadal) variations in both precipitation and non-precipitation duration in Southwest China, addressing a gap in previous studies.
• Identifies the Yunnan-Guizhou Plateau as a key region exhibiting statistically significant changes in precipitation duration and a regime shift around the early 2000s.
• Elucidates the distinct large-scale atmospheric circulation patterns and their teleconnections with specific Sea Surface Temperature Anomalies (SSTA) (PDO for inter-decadal, equatorial western Indian Ocean SSTA for inter-annual) that drive these multi-timescale variations.
• Contributes to a deeper understanding of drought and flood formation mechanisms in Southwest China, offering a scientific basis for local disaster prevention and mitigation.

Funding

• Natural Science Foundation of Chongqing, China (grant numbers: cstc2021jcyj-msxmX0913 and CSTB2022NSCQ-MSX0558)
• National Natural Science Foundation of China (grant numbers: 41875093 and 41875111)

Citation

@article{Zhou2026Multitimescale,
  author = {Zhou, Jie and Zhao, Junhu and Li, Yonghua and Tang, Hongyv and FENG, Guolin},
  title = {Multi-timescale characteristics and possible causes of summer precipitation duration in Southwest China},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-025-06014-9},
  url = {https://doi.org/10.1007/s00704-025-06014-9}
}