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June–July mean temperature was reconstructed back to 1698 for the southern Altai Mountains in eastern Central Asia using four temperature series based on tree-ring widths. The reconstruction explains 48% of the variation in the observed temperature from 1962 to 2003. Warm periods occurred during 1714–1732, 1753–1776, 1800–1840, 1866–1886, 1893–1911, and 1943–1969, while the periods of 1708–1713, 1733–1752, 1777–1799, 1841–1865, 1887–1892, 1912–1942, and 1970–1993 were relatively cold. Power spectral and wavelet analyses demonstrated the existence of significant 50-, 14-, 2.8-, and 2.5-year cycles of variability. The results of a spatial correlation analysis suggested that this temperature reconstruction contains climatic signals for a large area of Central Asia. After employing a 21-year low-pass filter, the coherence of the newly reconstructed series with a regional temperature reconstruction for Central Asia and also with a local temperature reconstruction for the Zajsan Lake area of East Kazakhstan indicates that our temperature reconstruction captures broad-scale regional climatic variations in the low-frequency domain. [ABSTRACT FROM AUTHOR]

In Central Asia, tree rings provide one of the best sources of paleoclimatological information. However, dendroclimatology has not been widely applied in the coniferous forests of Central Asia. Tree cores of Picea Schrenkiana from four sites in the Hutubi River Basin were developed into a 606-year tree-ring width chronology. The analyses showed that the tree-ring width indices highly correlate with mean April–May PDSI in the Hutubi River Basin. Mean April–May PDSI of the Hutubi River was reconstructed using the tree-ring data with 41.5% of the variance explained. The reconstructed series contains both high- and low-frequency climate signals. Our new PDSI reconstruction agrees reasonably well with the dry and wet periods previously estimated from tree rings in western Tien Shan. The results reveal common climatic extremes over much of Central Asia. Spatial analysis shows that the PDSI reconstructions have strong common signals for the Tien Shan. The first principal component of PDSI reconstructions in Tien Shan is significantly correlated with sea surface temperature in the eastern equatorial Pacific Ocean and Atlantic Ocean. The linkages to the Atlantic and Pacific Oceans suggest the connection of regional moisture variations to the Asian monsoon and the Westerlies. [ABSTRACT FROM AUTHOR]

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 developed three tree-ring width chronologies of Dragon Spruce ( Picea likiangensis var. balfouriana) from Qamdo region in the eastern Tibetan Plateau. It was found that the autumn–winter mean minimum temperature was the principal factor that limited the radial growth of Dragon Spruce. In particular, the tree-ring width chronology of the Changdu site was related significantly and positively with the autumn–winter mean minimum temperature. Using standard dendrochronological (STD) method, we obtained a 400-year reconstruction of October–January minimum temperature at the Qamdo meteorological station. The reconstruction explains 43.1% of the variance in the instrumental temperature records during the 1954–2006 calibration periods. It indicates that quasi-periodic changes exist on scales of 5, 11, and 102–103a. The temperature fluctuates around the mean and rises slowly from 1594 to the 1700s, following which the autumn–winter mean minimum temperature exhibited obvious stage changes with warmer periods (1769–1800, 1819–1849, 1873–1900, 1926–1954, 1987–2006) and colder periods (1716–1768, 1801–1818, 1850–1872, 1901–1925, 1955–1986). The temperature in the eastern Tibetan Plateau and the mean temperature in the Northern Hemisphere exhibited good consistency in the 20th century. From 1900 to the 1930s, the temperature rose slowly and then declined sharply in the 1940s. In the 1950s, the temperature rose, before falling again in the early 1960s, prior to a gradual increase following the late 1960s. The temperature in Qamdo represents the temperature of the southeastern Tibetan Plateau, and significant positive correlations were found with other temperature reconstructions on the southeastern Tibetan Plateau and the southern slopes of the Himalaya (including the Indian peninsula). The India-Burma Trough may have a certain effect on climate change in the eastern Tibetan Plateau. The reconstruction sheds new light on temperature variability and change in a region where the climate history for the past several centuries is poorly understood. [ABSTRACT FROM AUTHOR]

We developed six tree-ring width chronologies of Siberian spruce ( Picea obovata ) from the low elevation forest of the southern Altay Mountains in northern Xinjiang, China. Although the six chronologies come from different sampling sites, significant correlations existed among the chronologies ( r ≥ 0.477), and the first principal component (PC1) accounted for 72.2% of total variance over their common period 1825–2010. Correlation response analysis revealed that radial growth of Siberian spruce is mainly limited by a 12-month precipitation starting from July of the previous year to June of the current year. We therefore developed a July–June precipitation reconstruction spanning 1825–2009, which explained 65.5% of the instrumental variance for the period 1962–2009. The information of our precipitation reconstruction suggested that dry conditions existed for the periods 1829–1838, 1852–1855, 1876–1888, 1898–1911, 1919–1923, 1932–1936, 1943–1955, 1963–1968, 1973–1984 and 2007–2009, and wet conditions for the periods AD 1825–1828, 1839–1851, 1856–1875, 1889–1897, 1912–1918, 1924–1931, 1937–1942, 1956–1962, 1969–1972 and 1985–2006. Spatial climate correlation analyses with gridded land surface data revealed that our precipitation reconstruction contains a strong precipitation signal for the Altay Mountain ranges. Our reconstruction agreed with the moisture-sensitive tree ring width series of Siberian larch from the Altay Mountains of Mongolia on a decadal timescale. In addition, in contrast to a drying trend in north central China, a clear wetting trend has occurred in the southern Altay Mountains since 1980s. [ABSTRACT FROM AUTHOR]

Abstract: September–March mean temperature has been reconstructed to A.D. 1680 for the Kaiduhe River watershed on the southern slope of the Tien Shan Mountains, China, using the Picea schrenkiana tree-ring width. The reconstruction explains the variance of 47% in the observed mean temperature from 1953 to 2011. Power spectral and wavelet analyses demonstrated the existence of significant 50-year and 2- to 7-year cycles of variability. The results of the spatial correlations suggest that our reconstruction contains climatic signals for Central Asia. Warm periods occurred during 1696–1708, 1730–1748, 1784–1804, 1832–1855, 1892–1903, 1924–1928, 1937–1943, and 1987–2006; while the periods of 1685–1695, 1709–1729, 1749–1783, 1805–1831, 1856–1891, 1904–1923, 1929–1936, and 1944–1986 were relatively cold. The significant correlation coefficient between the reconstruction and the temperature reconstruction for the Urumqi River source reveals that the temperature variations in the annual cold period for the southern and the northern slope of the central Tien Shan Mountains are roughly synchronous over the last nearly 300 years. A comparison between the reconstruction and three winter North Atlantic Oscillation indexes revealed similar long-term trends. [Copyright &y& Elsevier]

Abstract: Three tree-ring maximum latewood density chronologies were developed from high elevation Picea schrenkiana sites in the western Tien Shan Mountains using different detrending methods. The new chronologies extend back to the early 16th and late 17th centuries, and contain significant late spring and summer temperature signals, respectively. An assessment of varying detrending methods and band-pass filtering the chronologies revealed only slightly differing low frequency trends retained in the maximum latewood densities. The distance between sampling sites and the varying seasonality of limiting climatic factors are identified as key drivers affecting the correlation among the maximum latewood density records in the study region. The new chronologies represent reliable proxies of high elevation late spring and summer temperature variability in an area underrepresented by such data, and are ready-to-use for network analyses addressing longer-term climate variations in eastern central Asia. [Copyright &y& Elsevier]

Abstract: Drought is a recurring phenomenon in north-central China. Long-term information about the history of drought is still limited because the instrumental records for many areas in north-central China go back only a few decades at best. This paper presents an earlywood width (EWW) chronology of Chinese pine (Pinus tabulaeformis) in the Shimen Mountains, Tianshui, eastern Gansu, north-central China. The climate-response analysis shows that April–July precipitation is the main factor limiting the earlywood growth of Chinese pines in the Shimen Mountains, Tianshui. Based on the EWW chronology, an April–July precipitation reconstruction for the period A.D. 1629–2008 was developed for Tianshui. The climate/tree-growth model accounts for 41.6% of the observed precipitation variance during the period 1953–2008. Spatial analysis shows that the precipitation reconstruction contains a strong common drought signal for north-central China. Reconstructed drought events are compared to a precipitation reconstruction of Huashan and historical archives for north-central China. The results reveal common climatic extremes over much of north-central China. Moreover, some dry periods coincided with solar minima or volcanic eruptions over the past several hundred years. Multi-taper spectral analysis reveals the existence of significant 3.8-year (90%), 3.1-year (95%), 2.7-year (99%), 2.4-year (99%) and 2.0-year (99%) periods of variability. The linkages to the Asian-Pacific Oscillation Index suggest regional precipitation variations may be linked to the East Asian summer monsoon circulations. [Copyright &y& Elsevier]

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]