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<p>Precipitation anomaly patterns (PAPs) in the Yangtze-Huai River Valley (YHRV) critically affect water resources, agricultural output, and the safety of hundreds of millions of people. Yet, their robust classification and associated atmospheric circulation features remain inadequately understood. This study develops an improved classification scheme to identify and characterize PAPs over the YHRV from 1951 to 2020. Based on precipitation data from 50 meteorological stations and ERA5 reanalysis, we identify nine distinct PAP types with high statistical reliability, with average pattern correlations ranging from 0.41 to 0.85 and average sign probabilities from 0.62 to 0.9 across types. The approach successfully identifies nine statistically robust and physically distinct PAPs, significantly improving upon conventional classifications by enhancing composite correlation for 78.7% of the years analyzed. The analysis reveals a distinct temporal shift, wherein the frequency of major drought patterns declined markedly from 15 cases (1951–1985) to 5 cases (1986–2020). Composite analysis uncovers the distinct atmospheric mechanisms governing these patterns: the extreme region-wide wet pattern (RWP) is characterized by a strong North Asian blocking high at upper levels, which facilitates a low-level cyclonic circulation that funnels moisture into YHRV. Conversely, region-wide dry (RWD) patterns are associated with a deep continental trough and a low-level anticyclone that effectively blocks moisture influx. By providing a physically coherent framework that links specific precipitation outcomes to large-scale circulation, these findings offer a refined basis for improving seasonal forecasting and developing more targeted strategies for disaster prevention in this vital region.</p>

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Optimized classification reveals typical summer precipitation anomaly patterns and associated circulation features over the Yangtze-Huai river Valley

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Liaofeng Liang,
  • Jun Xia,
  • Juying Chen,
  • Zhonggen Wang

摘要

Precipitation anomaly patterns (PAPs) in the Yangtze-Huai River Valley (YHRV) critically affect water resources, agricultural output, and the safety of hundreds of millions of people. Yet, their robust classification and associated atmospheric circulation features remain inadequately understood. This study develops an improved classification scheme to identify and characterize PAPs over the YHRV from 1951 to 2020. Based on precipitation data from 50 meteorological stations and ERA5 reanalysis, we identify nine distinct PAP types with high statistical reliability, with average pattern correlations ranging from 0.41 to 0.85 and average sign probabilities from 0.62 to 0.9 across types. The approach successfully identifies nine statistically robust and physically distinct PAPs, significantly improving upon conventional classifications by enhancing composite correlation for 78.7% of the years analyzed. The analysis reveals a distinct temporal shift, wherein the frequency of major drought patterns declined markedly from 15 cases (1951–1985) to 5 cases (1986–2020). Composite analysis uncovers the distinct atmospheric mechanisms governing these patterns: the extreme region-wide wet pattern (RWP) is characterized by a strong North Asian blocking high at upper levels, which facilitates a low-level cyclonic circulation that funnels moisture into YHRV. Conversely, region-wide dry (RWD) patterns are associated with a deep continental trough and a low-level anticyclone that effectively blocks moisture influx. By providing a physically coherent framework that links specific precipitation outcomes to large-scale circulation, these findings offer a refined basis for improving seasonal forecasting and developing more targeted strategies for disaster prevention in this vital region.