Mechanisms of Mediterranean Region Hydroclimate Variability and Change

干旱长期以来一直是地中海周边国家的担忧，从伊比利亚半岛到北部的土耳其，从摩洛哥到南部海岸的叙利亚。 该地区的大部分地区在 20 世纪下半叶经历了长期干旱，最近叙利亚的动乱是在新月沃地发生特别严重的干旱之后发生的。 此外，气候模型在预测 21 世纪地中海周围的强烈干燥趋势方面非常一致。该项目旨在了解驱动地中海地区降水和蒸发自然变化和强迫变化的动力机制。 通过使用基于树木年轮的气候重建来扩展观测记录，为近几十年来的干旱提供长期背景。 其他工作考虑了地中海气旋在区域降水变化中的作用，以及可能导致气候模型中未来干燥的气旋行为的变化。 使用线性驻波模型和其他诊断技术来检查喷射流变化在未来干燥中的作用。 使用基于观测的再分析产品和气候模型输出进行彻底的水分收支分析。 先前的研究表明，地中海的大部分水文气候变化与北大西洋涛动有关，北大西洋涛动涉及大西洋急流和风暴路径的南北偏移。 PI 的初步工作表明，这种变化可以与气候变暖导致的干旱区分开来。 这项工作还包括努力开发地中海水文气候的概率预测，其中考虑到模拟过去变化的模型技能。如上所述，由于大范围干旱对人类的影响以及未来地中海干旱的模型预测有些可怕，这项工作具有很大的社会相关性。 鉴于一种模型与另一种模型的一致性，这些预测是合理的，但在长期气候记录的背景下对潜在机制的检查可以在很大程度上评估其有效性。 PI 通过 MedCLIVAR 参与地中海气候并影响社区，MedCLIVAR 是一个研究协调网络，开展的活动包括针对地中海气候的研讨会、学校和交流项目。 言归正传，该项目通过拉蒙特暑期实习计划与本科生互动，并通过一年两次的拉蒙特开放日进行外展。 该项目还为博士后研究学者提供支持和培训，从而培养该研究领域的劳动力。

Drought has long been a concern for the countries surrounding the Mediterranean, from the Iberian Peninsula to Turkey on the north and from Morocco to Syria along the southern shore. Much of the region experienced prolonged drying in the second half of the 20th century, and the recent turmoil in Syria follows a particularly acute drought in the Fertile Crescent. Moreover, climate models are remarkably consistent in projecting a strong drying trend around the Mediterranean over the 21st century.This project seeks to understand the dynamical mechanisms that drive natural variability and forced change in precipitation and evaporation over the Mediterranean region. The observational record is extended through the use of tree ring - based climate reconstructions to give long-term context to the drying of recent decades. Other work considers the role of Mediterranean cyclones in regional precipitation variability, along with changes in cyclone behavior that may contribute to the future drying seen in climate models. The role of jet stream shifts in future drying is examined using a linear stationary wave model and other diagnostic techniques. A thorough moisture budget analysis is carried out using both observationally-based reanalysis products and climate model output. Previous work shows that much of the hydroclimate variability in the Mediterranean is linked to the North Atlantic Oscillation, which involves a north-south shift of the Atlantic jet stream and storm track. Preliminary work by the PIs suggests that this variability can be distinguished from aridity occurring as a consequence of a warming climate. The work also includes an effort to develop probabilistic projections of Mediterranean hydroclimate that take into account the skill of models in simulating past variability.As noted above, the work has great societal relevance due to the human impacts of widespread drying and the somewhat dire model projections of future Mediterranean aridity. The projections are plausible given their consistency from one model to another, but an examination of the underlying the mechanisms, in the context of a long-term climate record, can do much to assess their validity. The PIs engage with the Mediterranean climate and impacts communities through MedCLIVAR, a research coordination network which conducts activities including workshops, schools, and exchange programs focused on Mediterranean climate. Closer to home, the project engages with undergraduate students through the Lamont Summer Intern Program and conducts outreach through the biannual Lamont Open House. The project also provides support and training for a postdoctoral research scholar, thereby developing the workforce in this research area.