Reconstruction of past hydroclimate variability in Iran from a multi-centennial and multi-parameter juniper tree-ring network

建议的项目旨在在气候敏感的半干旱地区伊朗建立一个多参数杜松树年轮网络，以年分辨率重建过去几个世纪的自然水文气候变化。研究的树木年轮参数包括树木年轮宽度（TRW）、树木年轮纤维素稳定氧同位素变化（<s:1> 18OTRC）和定量木材解剖特征（QWA），以此来评估伊朗桧抗旱能力的生态适应性。由于不同的树木年轮参数对不同季节周期的气候变量敏感，因此可以识别不同季节、不同气候原因导致的干旱事件。由于该网络方法综合了伊朗受不同空气湿度源影响的气候对比地区的树木年轮站点，它使我们能够检测主要大气环流模式强度的变化及其对伊朗水文气候变化和极端水文事件的影响。特别强调深入分析极端水文气候事件的频率、强度和持续时间在不同时间尺度上的长期变化，从数年到数十年和数百年。在选定的指针年，将应用反向轨迹模拟来确定主要大气水分来源和树轮网络上相关的大气流动模式的区域差异。这一程序将使我们能够探测过去40年来伊朗不同地区导致极端气候事件的水分输送途径的变化。来自中亚西部邻近地区的现有杉木<s:1> 18OTRC年表将与我们的数据相结合，研究来自以西风冬季降水为主的地区与亚洲夏季风系统的水文气候信号之间的大尺度遥相关。通过这样做，可以确定这两个重要环流系统强度的时间变化及其对伊朗干旱风险的影响。

The suggested project aims to establish a multi-parameter juniper tree-ring network over the climate-sensitive semiarid Iran to reconstruct natural hydroclimate variability over the past centuries at annual resolution. The investigated tree-ring parameters include tree-ring width (TRW), stable oxygen isotope variations in tree-ring cellulose (18OTRC,) and quantitative wood anatomical features (QWA), from which ecological adaptations in the drought resilience of Iranian junipers will be evaluated. Since the various tree-ring parameters are sensitive to different climate variables over the seasonal cycle, drought events occurring in different seasons and due to different climatic reasons can be identified. Since the network approach integrates tree-ring sites from climatically contrasting regions over Iran that are influenced by different air moisture sources, it enables us to detect variations in the strength of major atmospheric circulation patterns and their impact on hydroclimate variations and extreme hydrological events over Iran. Special emphasis lies on an in-depth analysis of long-term variability of the frequency, intensity, and duration of extreme hydroclimatic events on different time scales from years to decades and centuries. Backward trajectory modelling will be applied to identify regional differences in dominant atmospheric moisture origins and related atmospheric flow patterns over the tree-ring network in selected pointer years. This procedure will allow us to detect changes in moisture transport pathways leading to extreme climate events in different parts of Iran over the past ca. 40 years. Existing juniper 18OTRC chronologies from neighboring areas in West-Central Asia will be combined with our data to study large-scale teleconnections between hydroclimatic signals originating from regions dominated by the westerly winter precipitation regime versus the Asian summer monsoon system. In doing so, temporal shifts in the strengths of these two important circulation systems and their impact on drought risk in Iran can be identified.