The role of anthropogenic aerosol in near-future sub-Saharan precipitation

撒哈拉以南非洲人口密集，对气候变化高度敏感。过去50年来，西非经历了长时间的干旱和不断增加的洪水，人们非常担心，气候风险的加剧将加剧现有的脆弱性。虽然萨赫勒地区历史上的干旱归因于气溶胶的增加，但非洲降水对气溶胶变化的响应却相对未被探索。目前几乎没有文献探讨气溶胶变化对东非降雨的影响。由于模式之间的差异，非洲降水预估存在很大的不确定性。在模拟大气对强迫的响应，特别是对气溶胶强迫的响应方面的差异，在这种不确定性中起着重要作用。来自偏远地区的气溶胶排放与推动若干非洲地区的历史变化有关，而在非洲也发现了未来排放的一些最大不确定性。目前对非洲预测信息的需求主要集中在近期，10-40年的时间尺度，气候适应。在推动短期预测的传播方面，气溶胶等短期污染物的变化比温室气体的作用要大得多。在这个项目中，气溶胶在非洲气候预测中的作用，以及这些预测中的不确定性，将通过三个研究问题来探讨：撒哈拉以南非洲的气候对未来潜在的人为气溶胶变化的反应是什么？-在非洲气候预估中，本地和远程气溶胶变化以及不同气溶胶种类的相对作用是什么？-西非和东非降水对区域气溶胶强迫的响应机制是什么？这些机制是否取决于模式气候学、模式过程表征或内部变率？为了解决这些问题，学生将有机会接触到一组新的耦合模式实验，旨在探索气溶胶在近期预测中的作用，并很容易与决策中通常使用的预测进行比较。学生将进行理想的实验，以帮助诊断重要的机制。有可能扩大这些实验，以量化模式偏差的作用，或内部变率在对气溶胶变化的响应中的作用。这个项目为学生提供了一个机会，让他们成为一个科学主题的专家，随着气候变化和社会对气候风险增加的反应的进步，这个主题将变得越来越相关。预计降水变化的区域人口众多，正在经历相当大的发展，需要采取缓解措施。因此，该项目可能会为IPCC的下一次评估提供信息。

Sub-Saharan Africa is densely populated and highly sensitive to climate change. West Africa has experienced both prolonged periods of drought and increased flooding over the last 50 years, and there is substantial concern that intensifying climate risk will exacerbate existing vulnerabilities. Although historical Sahel drought has been attributed to aerosol increases, African precipitation responses to aerosol changes are relatively unexplored. There is almost no existing literature exploring the impact of aerosol changes on East African rains. There are large uncertainties in projections of African precipitation due to differences between models. Differences in the simulation of the atmospheric response to forcing, and the response to aerosol forcing in particular, play an important role in this uncertainty. Aerosol emissions from remote regions have been implicated in driving historical changes in several African regions, while some of the largest uncertainties in future emissions are also found over Africa. Much of the current requirement for projection information for Africa focuses on near-term, 10-40-yr time scale, climate adaptation. Changes in short-lived pollutants like aerosols play a much stronger role than greenhouse gases in driving the spread of near-term projections. In this project, the role of aerosol in African climate projections, and the uncertainties in these projections, will be explored through three research questions: - What is the response of sub-Saharan African climate to potential future anthropogenic aerosol changes? - What are the relative roles of local and remote aerosol changes, and different aerosol species, in climate projections for Africa? - What are the mechanisms for West African and East African precipitation responses to regional aerosol forcing? Do these mechanisms depend on model climatology, model process representation, or internal variability? To address these questions, the student will have access to a new set of coupled model experiments, designed to explore the role of aerosol in near-term projections and be easily comparable to projections typically used in decision making. The student will perform idealised experiments to aid diagnosis of important mechanisms. There is the potential to expand these experiments to quantify the role of model biases, or the role of internal variability, in the response to aerosol changes. This project is an opportunity for the student to become an expert in a scientific topic that will become increasingly relevant as climate change, and societal responses to increased climate risk, progress. The regions where precipitation changes are expected have a large population and are undergoing considerable development with a need for mitigation. The project will thus potentially inform the next assessment of the IPCC.