[Precipitation variation reconstructed based on tree-ring width data for the past 399 years in the eastern Yinshan Mountains, China]. / åŸºäºŽæ ‘è½®å®½åº¦æ•°æ®é‡å»ºçš„é˜´å±±ä¸œéƒ¨è¿‡åŽ»399年降水变化.

Based on the tree-ring increment cores of Pinus tabuliformis collected from the eastern Yinshan Mountains, the tree-ring width chronology was developed. The correlation coefficients were calculated between the chronology and monthly mean temperature and monthly precipitation during the instrumental period of AD 1952-2007. The results showed that the highest correlation was found between the total precipitation from September of previous year to June of current year and the chronology (r=0.73, n=56, P<0.01). Based on the correlation, the September of previous year to June of current year total precipitation variation was reconstructed in the eastern Yin-shan Mountains during the past 399 years (AD 1619-2017). The reconstruction explained 54.9% of the variation in the total precipitation from September of previous year to June of current year for the calibration period (AD 1952-2007). Both the 'leave-one-out' cross validation and split-period validation showed that the model was relatively robust, with sufficient skills of estimation and high reliability. At the decadal scale, there were four wet periods (AD 1619-1663, AD 1705-1711, AD 1945-1963, and AD 1979-2017)) and four dry periods (AD 1734-1767, AD 1786-1814, AD 1839-1867, and AD 1888-1942) in the past 399 years. Among those periods, the AD 1979-2017 was the wettest period, and AD 1888-1942 was the longest dry duration with the driest period at the late 1920s. Results of power spectral analysis revealed cyclic fluctuations of precipitation series on 2-7 years and 125 years. In addition, the comparison with other reconstructions and spatial correlation analysis indicated that the reconstructed precipitation series well represented regional scale precipitation variation.

[Influence of large volcanic eruptions on climate as revealed by tree-ring data on the Tibetan Plateau, China]. / æ ‘è½®æ•°æ®æ­ç¤ºçš„å¼ºç«å±±å–·å‘å¯¹é’è—é«˜åŽŸåœ°åŒºæ°”å€™çš„å½±å“.

Large volcanic eruption is an important factor affecting global climate change. In the past few decades, many researchers reconstructed a number of climate series based on tree rings on the Tibetan Plateau, and examined the impacts of large volcanic eruptions on the climate. The results showed that these tree-ring sites used to examined the influences of large volcanic eruptions on climate change were primarily located in the eastern Tibetan Plateau. In addition, the series comparison and the superposed epoch analysis were main methods for studying the climate effects of large volcanic eruptions. Based on the results analyzed using two methods, we suggested that the large volcanic eruptions in low-mid latitudes had a significant impact on temperature and dry/wet variation. Cooling or drought occurred after large volcanic eruptions in the subsequent 1-2 years. How-ever, the large volcanic eruptions in high latitudes had minor impacts on climate change. Furthermore, consecutive multiple volcanic eruptions could result in cooling at the decades scale. The factors influencing the climate effects of large volcanic eruptions included the location of the volcanic eruptions, intensity of the volcanic eruptions, atmospheric circulation, etc. Finally, we proposed research projects that need to be carried out in the future.