Tree-ring based drought reconstruction at the northwestern margin of monsoon region of China since 1862

A tree-ring width chronology developed from three sites of Pinus tabulaeformis at the northwestern margin of the monsoon region of China was employed to study regional drought variability. The drought reconstruction, spanning 1862–2007, was developed by calibrating tree-ring data with the Palmer drought severity index (PDSI), an index indicating regional moisture conditions. The reconstruction accounted for 43.3% of actual PDSI variance during their common period (1948–2005). Droughts lasting over four years were found in 1877–1885, 1889–1893, 1925–1932, and 2004–2007, among which the droughts epochs in 1877–1885 and 1925–1932 were the two most severe and long lasting in the study area since 1862. There was an aridity aggravation trend since the mid-1970s in the reconstructed series, which was consistent with the global temperature rise in records since 1975. This study indicated the feasibility of combining tree-rings and the PDSI to reconstruct large-scale drought patterns over this area, and the PDSI reconstructed by tree ring may be a good proxy for the adjacent desert evolution.