Adjusting Standardized Precipitation Index to Analyze Long-Term Drought Patterns from Documentary Records in the Chinese dynasties Since the Mid-14th Century

This study integrates modern observational data (CRU)(1901-2023) with historical documentary records (REACHES) to reconstruct and analyze long-term drought patterns in the Chinese dynasties since the mid-14th centuries (1368-1911). By focusing on the Standardized Precipitation Index (SPI), we examine spatio-temporal drought trends across multiple timescales. SPI indices for 12-month, 36-month, and 60-month periods (SPI12, SPI36, SPI60) were calculated to capture variability across different temporal scales. Empirical orthogonal function (EOF) analysis was conducted to identify major spatial patterns and analyze temporal series, facilitating the identification of extreme drought periods and sequences of significant anomalies. Wavelet analysis was employed to detect potential periodicities and dominant cycles within the data. Further analysisis underway to assess whether variations in drought patterns might differ when considering evapotranspiration (SPEI). This aspect remains exploratory, offering a potential insight into the broader implications of integrating long-term and additional climatic variables into drought analysis.