Influence of May–June frontal precipitation on coherent moisture pattern in east-central China since 1793 based on tree-ring data

The short and scare record limits to understand the history of the hydroclimate change in east-central China. In this study, we developed a 225-year tree-ring width chronology (STD) for Chinese pine originating from the Shiren Mountain in Henan Province, east-central China. We analysed the correlation between the STD and different climatic factors and then reconstructed the May–June moisture variation, which is one of the longest moisture variation reconstruction based on tree-ring width in this region. Further, the results of the spatial analysis between our reconstruction and actual moisture variation revealed that our reconstruction is representative of large-scale May–June self-calibrating Palmer Drought Severity Index (scPDSI) in east-central China. Additionally, the reconstruction showed five relatively dry and five relatively wet epochs over the past 225 years. It also showed that the moisture variation in the study area is similar to those corresponding to other nearby sites and could be validated by historical documents; these findings demonstrate the reliability of our reconstruction back in time. Furthermore, we detected the reason for the coherent May–June moisture change in east-central China. It showed that the actual scPDSI showed significantly positive correlations with concurrent precipitation. Additionally, regression analyses showed that precipitation is largely determined by the frontal system, which is also responsible for the coherent May–June moisture pattern observed in east-central China. In addition, the result of spectral analysis and correlation patterns of the reconstructed scPDSI with global sea surface temperatures indicated that the El Niño-Southern Oscillations might be the forcing mechanism for regional moisture variability.