现代环境研究室知识库

A robust regional tree-ring chronology with a span of 1819-2009 was developed for the Hulun Buir steppe, China, a region in the eastern edge of the Mongolian Plateau. This chronology exhibited significantly positive correlation with precipitation in June, and negative correlations with temperature from April to September except for May. Highest correlation was found between tree rings and the average April-August standardized precipitation evapotranspiration index (SPEI), suggesting that pines growth strongly respond to the seasonal drought conditions. Accordingly, the average April-August SPEI reconstruction was performed for the period 1854-2009, explaining 45.5 % variance of the calibration period 1953-2009. New reconstruction shows some synchrony with regional-scale events found in other reconstructions to the west Mongolian Plateau. The recent droughts in late 1990 to present are not unusual in the context of the past several centuries. Spectrum analyses suggested that the average April-August SPEI variations, especially severe droughts in the late 1870s-early 1880s, 1920s and since the late 1990s could be associated with large-scale climate forcing, such as the El Nio-Southern Oscillation, the Pacific Decadal Oscillation and the summer North Atlantic Oscillation. Significant teleconnections indicated drought variability during the past several centuries in eastern Mongolian Plateau existed close connections with large-scale synoptic features.