Regional extreme climate events on the northeastern Tibetan Plateau since AD 1450 inferred from tree rings
Regional extreme climate events on the northeastern Tibetan Plateau since AD 1450 inferred from tree rings
复制标题
DOI：
10.1016/j.gloplacha.2010.10.013
复制
发表时间：
2011-02
影响因子：
3.9
通讯作者：
C. Qin;Bao Yang;A. Bräuning;D. Sonechkin;Kai Huang
中科院分区：
文献类型：
--
作者：
C. Qin;Bao Yang;A. Bräuning;D. Sonechkin;Kai Huang
祁连杜松（Juniperus przewalskii Kom.）是我国西北干旱地区青藏高原东北部朝南山坡上分布广泛的树种。我们根据两个新的年表和四个先前发布的年表建立了树轮宽度网络。相关性和响应函数分析表明降水对径向生长有积极影响。尽管当地气候与增长关系存在微小差异，但去年 7 月和当前 6 月之间的年度窗口降水量在所有研究地点都显示出与年轮宽度一致的正相关关系。与所谓的“指针年”方法类似，定义“异常”生长年是为了提取公元 1450 年至 2006 年期间的极端气候事件。我们定义了一个干湿等级系列，其中包含从异常年份分析推断出的五个等级的气候事件。近50年来，湿润事件发生频率明显增加，干旱事件发生频率明显减少，这意味着如果区域变暖持续下去，未来青藏高原东北部出现干旱年的概率将进一步降低。将我们的代理记录与中国东部的历史干湿记录相结合，我们绘制了中国大部分地区的干湿模式。通过分析极端事件年中国850hPa气压模式，我们发现冷热空气汇合是青藏高原东北部洪水事件的先决条件。因此，以贝加尔湖南部为中心的逆时针大气环流仅发生在洪水事件年。
Qilian juniper (Juniperus przewalskii Kom.) is a widely distributed tree species growing on south-facing slopes in the northeastern Tibetan Plateau in arid northwestern China. We established a tree-ring width network based on two new chronologies and four previously published chronologies. Correlation and response function analyses demonstrate that precipitation positively influences radial growth. Despite of minor differences in local climate–growth relations, precipitation for the annual window between previous July and current June shows consistent positive correlations with ring width at all study sites. Similar to the so called ‘pointer year’ approach, ‘anomalous’ growth years were defined to extract extreme climate events for the period AD 1450–2006. We defined a dryness–wetness grade series with five grades of climate events inferred from anomalous year analysis. During the last 50years, the frequency of wet events increased and that of drought events decreased noticeably, implying that the probability of occurrence of dry years in the northeastern Tibetan Plateau will further decrease in the future if regional warming continues. Combining our proxy records with a historical dryness–wetness record from eastern China, we mapped dryness–wetness patterns over large parts of China. By analyzing the atmospheric pressure patterns at the 850hPa level over China for selected extreme event years, we found that the confluence of cold and hot air is a precondition for a flood event in the northeastern Tibetan Plateau. Thus, a counter-clockwise atmospheric circulation centered in south of Lake Baikal only occurs in flood event years.