Abstract: A drought index series reconstruction for north-central China was presented based on tree-ring-width chronologies developed from three sites of Pinus tabulaeformis in the northern Helan Mountains. The drought index reconstruction, spanning 1759-2005, was developed by calibrating the tree-ring-width chronologies with the Palmer drought severity index (PDSI), which describes the regional moisture condition properly. The reconstructed PDSI in May-July (PDSI5-7) was verified with independent data, and accounted for 47.90% of the actual PDSI5-7 variance during their common period (1953-2005). The mean of PDSI5-7 over 1759-2005 was estimated at -0.41. The full reconstruction indicates that the regional drought variability was relatively stable during the nineteenth century, but became more variable and persistent during the twentieth century. The drought epoch in the late 1920s was the severest one and the 1870s and 1940s were two wetter decades in our reconstruction.

Key words: Mt. Helan, tree-ring width, PDSI reconstruction