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

建议的项目旨在建立一个多参数的杜松树轮网络，气候敏感的半干旱伊朗重建自然水文气候变化在过去几个世纪的年度分辨率。调查的树轮参数包括树轮宽度（TRW），稳定氧同位素的变化在树轮纤维素（1018OTRC，）和木材的定量解剖特征（QWA），从伊朗杜松的干旱适应性的生态适应将进行评估。由于不同的树木年轮参数对季节周期内不同的气候变量敏感，因此可以识别出不同季节和不同气候原因造成的干旱事件。由于网络的方法集成了树木年轮网站从伊朗的气候对比鲜明的地区，不同的空气水分来源的影响，它使我们能够检测主要大气环流模式的强度变化及其对伊朗的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在几年到几十年和几个世纪的不同时间尺度上的频率、强度和持续时间的长期变化。将采用后向轨迹模型，以确定在选定的指针年树木年轮网络上主要大气水分来源和相关大气流动模式的区域差异。这一过程将使我们能够检测在过去的一年中，在伊朗不同地区导致极端气候事件的水分输送途径的变化。40年现有的杜松18OTRC年表从邻近地区在中亚西部地区将结合我们的数据，研究大规模的遥相关水文气候信号来自西风冬季降水制度占主导地位的地区与亚洲夏季风系统。在这样做的时候，这两个重要的环流系统的强度的时间变化及其对伊朗干旱风险的影响可以确定。

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.