Warm-season hydroclimate variability in Central China since 1866 AD and its relations with the East Asian Summer Monsoon: evidence from tree-ring earlywood width

Abstract. Historical hydroclimate records derived from tree-ring parameters are scarce in the core region of East Asian Summer Monsoon (EASM) in China, limiting our understanding of the inter-decadal hydroclimate variability of this region and its possible connections with the EASM. In this study, standard chronologies of total tree-ring width (TRW), earlywood width (EWW), and latewood width (LWW) were created using tree-ring samples of Pinus tabulaeformis in the eastern Qinling Mountains, Central China. The strongest growth-climate relationship was found between EWW and May–July self-calibrated Palmer Drought Severity Index (MJJ scPDSI). Therefore, a linear regression model, which explained 50.3 % of the variance in MJJ scPDSI (1951–2005), was developed to estimate the past MJJ scPDSI variations using EWW. The time series of MJJ scPDSI was extended back to the year 1866, and validated by independent hydroclimate series from nearby regions. Before the mid-1950s, the variations of MJJ scPDSI were in-phase with those of EASM intensity on decadal and longer timescales, suggesting that wet conditions would occur in the eastern Qinling Mountains when EASM was strengthened. Since the mid-1950s, however, the relationship has been out-of-phase. This phase change may be associated with an intensified dipole pattern of EASM precipitation.