A 225-year long drought reconstruction for east Xinjiang based on Siberia larch (Larix sibirica) tree-ring widths: Reveals the recent dry trend of the eastern end of Tien Shan

A tree-ring width chronology developed from a site of Larix sibirica at the eastern end of Tien Shan was employed to study the drought variability of east Xinjiang. The drought reconstruction spanning 1785–2009 was developed by calibrating tree-ring data with standardized precipitation-evapotranspiration index (SPEI), an index indicating regional moisture conditions. The SPEI reconstruction accounted for 45.8% of actual October–August SPEI variance during their common period (1957–2009). Wet periods with SPEI above the 225–year mean occurred around 1785–1799, 1821–1833, 1842–1858, 1864–1873, 1887–1898, 1905–1925, 1937–1948, 1954–1962, 1969–1983 and 1991–1993, while dry periods (SPEI below the mean) occurred in 1800–1820, 1834–1841, 1859–1863, 1874–1886, 1899–1904, 1926–1936, 1949–1953, 1963–1968, 1984–1990 and 1994–2009. There was an aridity aggravation trend since the mid-1980s in east Xinjiang. Our results also suggest that east Xinjiang was influenced by the interactions between the Asian monsoon and the Westerlies circulations.