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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. [ABSTRACT FROM AUTHOR]

We have reconstructed the Palmer Drought Severity Index (PDSI) from 1580 to 2005 for Western Tian Shan, Central Asia, using tree rings of Picea schrenkiana. The reconstruction explains 35% of the actual January–May PDSI variance during the common period 1925–2005. Split-sample validation supports our use of the reconstruction model based on the full period of reliable observational data (1925–2005). Spatial climate correlation analyses with gridded PDSI data revealed that our PDSI reconstruction represents a strong regional drought signal for Western Tian Shan. Dry periods occurred during ad 1614–1628, 1700–1722, 1758–1790, 1806–1833, 1873–1898, 1908–1936, 1943–1951, 1960–1966 and 1973–1988; while the periods of ad 1580–1613, 1629–1699, 1723–1757, 1791–1805, 1834–1872, 1899–1907, 1937–1942, 1952–1959, 1967–1972 and 1989–present were relatively wet. Our reconstruction agrees reasonably well with the dry and wet periods previously estimated from tree rings in Tian Shan. Significant spectral peaks are identified at 2–5, 60.2 and 213 years. Our reconstructed drought is significantly correlated with sea surface temperature in the North Atlantic and Indo–West Pacific Oceans. The linkages to the North Atlantic and Indo–West Pacific Oceans suggest the connection of moisture variations of Central Asia to the westerly circulation and tropical ocean–atmosphere systems. [ABSTRACT FROM AUTHOR]

Abstract: July–June precipitation has been reconstructed back to A.D. 1464 for the Baluntai region on the southern slope of the central Tien Shan Mountains, China, using the Picea schrenkiana tree-ring width. The reconstruction explains the variance of 51% in the observed precipitation from 1959 to 2005. By employing a 21-year moving average to the reconstruction, nine periods with above average reconstructed precipitation comprised ∼1474–1503, 1550–1577, 1588–1619, 1658–1713, 1790–1812, 1833–1867, 1890–1907, 1923–1944, and 1988–1995∼; eight periods with below average reconstruction consisted of 1504–1549, 1578–1587, 1620–1657, 1714–1789, 1813–1832, 1868–1889, 1908–1922 and 1945–1987. The wet/dry periods of the reconstructed precipitation correspond well with other reconstructions. Some droughts in the historical documents are also precisely captured in the reconstruction. Precipitation variations for the southern slope of the central Tien Shan Mountains are roughly synchronous with that of the northern slope in the recent ∼300 year. Power spectral and wavelet analysis demonstrated the existence of significant ∼100-y, ∼60-y, ∼50-y, ∼16-y, ∼10-y and ∼2-y cycles of variability. [Copyright &y& Elsevier]