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的最大不确定性来源，阻碍了可信的边缘预测。随着我们进入后化石世界，预计ACI效应将发生巨大变化，其特点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。尽管我们预计与今天相比将有更清洁的云层，但由于气候变化和来源区域特征的变化，这种后化石状态的ACI可能与工业化前的条件有很大不同。CleanCloud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千米尺度气候模型中的代表性，量化和了解它们的区域和时间影响，以及它们将如何在向化石时代后的过渡中演变。为了实现这一目标，CleanCloud将1)在欧洲气候热点地区开展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)与卫星社区协调，帮助校准和验证即将到来的卫星任务；4)利用先进的机器学习、数据同化和模型校准，改进和更好地约束公里级和大尺度气候模型，面对现有和新的卫星和现场数据的扰动物理组合；5)评估气溶胶在对流系统生命周期中的作用，重点是降水的形成和对水文循环的影响；6)加强数据中心、测量计划、国际活动、实验室研究和模型的开发。通过这些，CleanCloud将深刻地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，并通过能够改善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.