P2C2: Extratropical Mechanisms, Land-Surface Properties, and Seasonal Precipitation Processes on Saharan Rainfall and Simulation of the African Humid Period

该项目的总体目标是加深对季节性非季风过程的了解，以便量化其对北方非洲气候变化的影响。 具体而言，该研究旨在深入了解西非季风（WAM），热带气旋，地中海冷空气激增和热带羽流对非洲湿润期（AHP）降雨（距今约14，800 - 5，000年）的相对贡献。在千年的时间尺度上，北方非洲经历了剧烈的气候和环境变化。在全新世早期到中期，撒哈拉沙漠是当今世界上最大的热沙漠，它得到了充足的降雨，并支持了广泛的湖泊，湿地和植被。 考虑到当今撒哈拉在地球辐射收支中的关键作用及其对萨赫勒降雨、全球矿物尘埃浓度、地球化学循环和热带气旋生成的影响，撒哈拉的气候变率，如全新世期间观察到的气候变率，对全球气候系统有着深远的影响。 通过评估这些过程对AHP降雨的贡献，研究将有助于解释撒哈拉-阿拉伯沙漠带代理记录中记录的水分来源，这些记录目前尚不明确，因为它们位于热带季风和中纬度降雨系统的边界附近。对社区地球系统模型（CESM）中新的动态土壤模拟方案的影响进行评估，将为气候模型的开发和改进AHP的模拟提供切实的见解。在大气环流模型中探测热带羽流的客观算法的开发将公开提供，并可用于研究过去、现在、2010年影响地球仪各地热带羽流事件的过程，更广泛的影响包括增加代表性不足的少数民族（URM）的管道的潜力通过我们参与密歇根大学（U-M）地球夏令营，学生进入地球科学。地球夏令营是一个为来自底特律地区的早期职业高中生开设的住宿夏令营，教育他们有关地球科学和地球科学职业的知识。 密歇根大学地球营由单一的夏季体验组成，但正在扩展为多夏令营，以增加学生在大学学习地球科学的可能性。作为我们参与地球营的一部分，该项目的参与者将为密歇根州安阿伯的第一次夏季体验开发和指导为期一天的大气科学和气候部分，并为怀俄明州的密歇根大学野外站的第二次夏季体验创建为期四天的部分。除了扩大URM在地球科学方面的参与外，该项目还将支持一名年轻科学家和至少一名本科生的培训和职业发展。

This project generally aims to develop an understanding of seasonal non-monsoon processes in order to quantify their contribution to climate change in northern Africa. Specifically, the research aims to provide insights into the relative contributions of the West African Monsoon (WAM), extratropical cyclones, Mediterranean cold air surges, and tropical plumes to African Humid Period (AHP) rainfall (~14,800 - 5,000 years Before Present. At millennial timescales, northern Africa experienced dramatic climate and environmental change. During the early to mid-Holocene AHP, the world's largest present-day hot desert, the Sahara, received abundant rainfall and supported widespread lakes, wetlands, and vegetation. Given the critical role of the present-day Sahara in Earth's radiation budget and its influence on Sahel rainfall, global mineral dust concentrations, biogeochemical cycles, and tropical cyclogenesis, climate variability in the Sahara, such as that observed during the Holocene, has profound impacts on the global climate system. By evaluating the contribution of these processes to AHP rainfall, the research will assist in interpreting the sources of moisture recorded in proxy records from the Sahara-Arabian desert belt which are currently ambiguous because they lie near the border of the tropical monsoon and mid-latitude rainfall regimes. An assessment of the impact of the new dynamic soil albedo scheme within the Community Earth System Model (CESM) will offer tangible insights for climate model development and improved simulation of the AHP. The development of an objective algorithm for the detection of tropical plumes within general circulation models will be made publicly available and could be used to study the processes that influence tropical plume events across the globe in past, present, and future climates.The Broader Impacts involve the potential for increasing the pipeline of underrepresented minority (URM) students into the earth sciences through our participation in the University of Michigan (U-M) Earth Camp. Earth Camp is a residential camp for early-career, high-school students from the Detroit-area that educates them about the earth sciences and careers in the earth sciences. The U-M Earth Camp has consisted of a single summer experience, but is expanding to a multi-summer camp in order to increase the odds that students will study earth sciences in college. As part of our participation in Earth Camp, the participants in this project will develop and instruct a one-day atmospheric science and climate component to the first summer experience in Ann Arbor, MI and create a four-day component for the second summer experience at the U-M field station in Wyoming. In addition to broadening URM participation in the earth sciences, this project will also support the training and career-development of a young scientist and at least one undergraduate student.