Changes in Impacts-relevant Climate in the World’s Mediterranean Climate Regions: A Mechanisms-based Investigation of Atmosphere-Ocean-Land Processes Across Seasons

地中海的气候特点是夏季温暖干燥，冬季温和潮湿，是世界著名的葡萄园和橄榄园的完美条件。但地中海气候并不是地中海沿岸国家独有的，因为美国西海岸、智利中部、南部非洲和澳大利亚西南部也存在类似的条件，所有这些都位于各自大陆的西海岸。这些地中海气候区(MCR)位于亚热带边缘，这意味着纬度低到足以在夏季处于干燥的副热带高压之下，但高到足以接受来自中纬度冬季天气系统的雨水。MCR的边缘位置使它们很容易受到与中纬度冬季和亚热带夏季相关的气候变化的影响：如果冬季风暴路径转移到更高纬度，这是温室气体变暖的预期结果，MCR可能会失去冬季雨水，而夏季可能会因为亚热带干旱地区的扩大而经历热浪和野火。考虑到加利福尼亚的狂风骤雨和热浪，以及随着大西洋风暴路径向北移动，西班牙上空的降雨量长期下降，MCRS的气候变化问题变得更加紧迫。本项目研究MCRS的气候变化，在其共同气候特征的框架内研究这一问题，并试图将地面气候变化与变暖引起的大气大范围环流变化联系起来。一个问题是，尽管这些地区有共同点，但它们的表现有很大不同，例如，加州没有经历过可与伊比利亚半岛相比的冬季降雨量的下降。该提案的具体目标是：1)确定风暴路径、急流、副热带高压、降水和温度的下沉和季节周期的变化，这些变化与全球大气环流的变化有关；3)确定与水资源、野火和农业相关的气候条件的诱发变化。一种紧急约束方法，在该方法中，模型模拟中当前气候的各个方面可以与观测结果进行核对，这些方面与来自相同模型的未来气候预测的行为有关。这种方法提供了一种方法，可以利用目前的观测来评估未来气候预测的可信度。鉴于这些地区人类和自然环境面临的危险，MCR在气候变暖中的命运是一个社会和科学利益问题。首席调查人员与MedCLIVAR合作，MedCLIVAR是International CLIVAR的一个子组，负责协调地中海气候研究。通过两年一度的拉蒙特开放日进行地方外联。该奖项为研究生提供支持和培训，从而在这一研究领域发展未来的科学队伍。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The climate of the Mediterranean features warm dry summers and mild wet winters, perfect conditions for its world-renowned vinyards and olive groves. But the Mediterranean climate is not unique to the countries bordering the Mediterranean Sea, as similar conditions exist on the US west coast, central Chile, southern Africa, and southwest Australia, all situated along the west coasts of their respective continents. These Mediterranean Climate Regions (MCRs) are found at the margins of the subtropics, meaning latitudes low enough to be under the dry subtropical anticyclones in summer but high enough to receive rain from the winter weather systems of the middle latitudes. The marginal location of the MCRs makes them vulnerable to changes in climate associated with both the midlatitude winter and the subtropical summer: if the winter storm paths shift to higher latitudes, an expected consequence of greenhouse warming, the MCRs could see loss of winter rain, while summers could experience heat waves and wildfires due to the expansion of the subtropical dry zones. The issue of climate change in MCRs has taken on some urgency given the wilfdires and heat waves in California and the long-term decline in rainfall over Spain as the Atlantic storm paths have shifted northward.This project examines climate change in the MCRs, examining the issue in the framework of their shared climatic features and attempting to relate climate change on the ground to warming-induced changes in the large-scale circulation of the atmosphere. One issue is the extent to which the regions behave differently despite their commonalities, for instance California has not experienced a decline in winter rainfall comparable to the Iberian Peninsula. The specific goals of the proposal are to 1) identify the changes in storms tracks, jet streams, subtropical highs, subsidence and seasonal cycles of precipitation and temperature that matter for each MCR, 2) relate these to changes in the global atmospheric circulation and 3) determine the induced changes in climatic conditions relevant to water resources, wildfire, and agriculture. An emergent constraint methodology, in which aspects of present-day climate in model simulations, which can be checked against observations, are related to the behavior of future climate projections from the same models. The methodology provides a way to use present-day observations to assess the credibility of future climate projections.The fate of MCRs in a warming climate is a question of societal as well as scientific interest given the hazards facing people and the natural environment in these regions. The Principal Investigators work with MedCLIVAR, a subgroup of International CLIVAR that coordinates Mediterranean climate research. Local outreach is conducted through the biennial Lamont Open House. The award provides support and training to a graduate student, thereby developing the future scientific workforce in this research area.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.