树轮记录的青海过去300年5-6月平均最高气温时空变化

利用位于青海不同地理单元的新建立的12个树轮年表和青海30个气象站的气象资料,采用REOF方法,分析了青海地区气温场和树轮宽度场特征;重建了青海过去300年5—6月平均最高气温。分析表明,青海气温场和树轮宽度场第一特征向量相关系数为-0.465(P0.01),两场的第一特征向量表现为同步变化,气温场和树轮宽度场第一特征向量高值中心位于青海北部的祁连山区和柴达木盆地,而低值中心位于青南高原西南部和东南部;过去300年青海气温大致可分为5冷5暖的变化阶段,存在5个明显的持续增温时段和4个持续降温时段,增温缓慢,降温迅速。最冷的时段为1830s—1840s年代,最长的偏冷期为19世纪末20世纪初,最暖的时段都发生在1930s—1950s年代,最长的偏暖期为18世纪末19世纪初。20世纪60年代以来,青海5—6月平均最高气温持续上升,尤其是80年代到现在,青海地区平均最高气温呈现急剧持续上升;过去300年青海地区5—6月平均最高气温具有2.1、3.1、8.5、25.5a和68.0a的变化准周期;青海5—6月平均最高气温受西风和印度季风影响较大;青海气候场重建序列的变化特征在一定程度上可代表青藏高原大部分地区甚至印度季风区5—6月平均最高气温。

The spatiotemporal variability of May-June maximum temperature in past 300 years on the Qinghai Plateau, according to tree ring records

In this study, tree ring samples of Sabina przewalskii were collected from 12 sites in the different geographical areas on the Qinghai Plateau. These were used to develop 12 tree ring width chronologies using standard dendrochronological methods. The characteristics of the temperature field and tree ring width field were analyzed, and the May-June maximum temperatures in past 300 years were reconstructed using 12 tree ring chronologies and meteorological data from 30 stations on the Qinghai Plateau. The analysis shows that the first eigenvector that is typical of the Qinghai temperature field and tree ring width has a field correlation coefficient of -0.465 (P < 0.01). The first characteristic change of the two fields is synchronization. The high value center of the first eigenvector is located at Qilian Mountains and Qaidam Basin on northern Qinghai, and the low center is located at southwest and southeast (Animaqing Mountains) on Qinghai Plateau. The May-June maximum temperature field in past 300 years had five warmer stages, five colder stages, and five continuous warming and four continuous cooling stages, with slow warming and rapid cooling. The coldest period was in the 1830s-1840s, the longest colder period was from late 19th century to early 20th century, the warmest period was in the 1930s-1950s, and the longest warm period was from late 18th to early 19th century. Since the 1960s, the temperature of May-June has risen continuously on the Qinghai Plateau, and it has risen particularly sharply from the 1980s to the present. We detected significant changes (P < 0.05) in the May-June maximum temperature field in past 300 years, with 2.1, 3.1, 8.5, 25.5-yr and 68.0year quasi-periodic changes. The May-June average maximum temperature was influenced by the southwest monsoon and westerly winds on the Qinghai Plateau. This work presents representative reconstructed temperatures for most of the Tibetan Plateau, even in the southwest monsoon region.