Clouds and climate transitioning to post-fossil aerosol regime (CleanCloud)

气溶胶-云相互作用（ACI）仍然是过去、现在和未来辐射强迫不确定性的最大来源，阻碍了可靠的气候预估。随着我们进入后化石时代，ACI效应预计将发生巨大变化，其特征是人为气溶胶排放大幅减少，但自然气溶胶的影响越来越大。尽管我们预计云将比今天更清洁，但由于气候的变化和源区特征的变化，后化石状态下的ACI可能与工业化前的条件有很大不同。“清洁云”将解决阻碍可靠的ACI评估的主要差距，改善它们在当前和下一代公里尺度气候模型中的代表性，量化和理解它们的区域和时间影响，以及它们将如何在向后化石时代过渡的过程中演变。为了实现这一目标，CleanCloud将1)在欧洲气候热点地区进行有针对性的实地试验；2)开发最先进的算法和分析工具，为关键的aci相关过程获得新的代理和诊断；3)与卫星界协调，为即将到来的卫星任务提供校准和验证；4)利用先进的机器学习、数据同化和模式校准，改进和更好地约束公里和大尺度气候模型，面对现有和新的卫星和原位数据的扰动物理集合；5)评估气溶胶在对流系统生命周期中的作用，重点关注降水形成及其对水文循环的影响；6)加强数据中心、测量计划、国际运动、实验室研究和模型的开发。有了这些，“清洁云”将大大加强欧洲对气候变化的研究，为即将到来的气候评估做出重大贡献，并通过改进天气和季节预测的模型造福社会。

Aerosol-cloud interactions (ACI) remain the largest source of uncertainty in past, present, and future radiative forcing, impeding credibleclimate projections. ACI effects are expected to change dramatically as we enter a post-fossil world, characterized by strong reductionsin anthropogenic aerosol emissions but with increasingly larger impacts from natural aerosols. Although we expect cleaner cloudscompared to today, ACI in this post-fossil state may considerably differ from preindustrial conditions, owing to shifts in climate andchanges in sources region characteristics. CleanCloud will address the major gaps impeding robust ACI assessments, improve theirrepresentation in current and next generation kilometer-scale climate models, quantify and understand their regional and temporal effects,and how they will evolve in the transition to the post-fossil regime. To accomplish this, CleanCloud will 1) carry out targeted fieldexperiments in European climate hotspots; 2) develop state-of-the-art algorithms and analysis tools to obtain new proxies and diagnosticsfor key ACI-related processes; 3) contribute to the calibration and validation of upcoming satellite missions in coordination with thesatellite community; 4) improve and better constrain kilometer- and large-scale climate models using advanced machine learning, dataassimilation and model calibration, confronting perturbed physics ensembles with existing and new satellite and in-situ data; and 5)assess the role of aerosols in the life cycle of convective systems, focusing on precipitation formation and the impacts on the hydrologicalcycle, and 6) enhance the exploitation of data centres, measurement programs, international campaigns, laboratory studies, and models.With these, CleanCloud will profoundly strengthen European Research on climate change, significantly contribute to upcoming climateassessments, and benefit society through models that enable improved weather and seasonal predictions.