Aridity changes in the eastern Qilian Mountains since AD 1856 reconstructed from tree-rings

This paper presents a drought reconstruction for the eastern Qilian Mountains based on a tree-ring width chronology developed from three sites of the Qinghai spruce (Picea crassifolia Kom.). The drought reconstruction, spanning the years 1856–2009, was developed by calibrating tree-ring data with the regional averaged Palmer Drought Severity Index (PDSI). The reconstruction explains 49.9% of the actual PDSI variance during the calibration period from 1951 to 2005. The reconstruction shows droughts occurred in the 1900s, the 1920s and early 1930s, and at the turn of the 21st century. Multi-taper method spectral analysis indicates the existence of some significant peaks at 2.6, 4.2 and 56.9 years. Drought variations in the study area are significantly correlated with sea surface temperatures in eastern equatorial Pacific Ocean, northern Indian Ocean, eastern China Sea and the Atlantic Ocean, suggesting a possible connection with the El Niño-Southern Oscillation, the Asian monsoon and the Westerlies.