Collaborative Research: RUI--Applying Measurements, Models, and Machine Learning to Improve Parameterization of Aerosol Water Uptake and Cloud Condensation Nuclei

大气气溶胶是大气中普遍存在的颗粒，由灰尘、煤烟、污染，甚至树木的自然排放组成。气溶胶对天气和气候至关重要，因为它们散射阳光，并作为形成云滴的基础。该奖项将为来自阿巴拉契亚州立大学和佐治亚理工学院的一个研究团队提供资金，以研究随着湿度的增加颗粒的生长，以及作为云滴基础的颗粒尺寸范围。气溶胶对气候的影响在政府间气候变化专门委员会(气专委)的报告中被强调为气候预测的一个关键不确定性。该项目具有显著的教育和培训效益，计划有8-12名本科生和硕士研究生参与该项目。阿巴拉契亚州立大学主要是一所本科大学，将受益于与一家研究密集型机构的合作。该奖项的主要科学目标是在北卡罗来纳州布恩的阿巴拉契亚州立大学的气溶胶网络站点培训、评估和应用经测量训练的模型来计算气溶胶液态水含量(ALWC)和云凝结核(CCN)光谱。ALWC不能直接测量，但可以从更常见的测量气溶胶光学性质中估计出来。2024年冬夏期间密集的实地活动将提供必要的数据，以开发、培训和评估将用于计算ALWC和CCN光谱的机器学习模型。然后，这些模型将被追溯到阿巴拉契亚圣地测量的历史数据库中，以研究气溶胶吸湿性、ALWC和CCN光谱如何以及为什么发生变化。更具体地说，研究人员将测试以下假设：1.机器学习模型，如随机森林，当使用具有地区代表性的颗粒物数量尺寸分布和气溶胶光学性质进行训练时，能够预测阿巴拉契亚圣地的ALWC和CCN光谱；2.美国东南部气溶胶成分的变化导致近年来在阿巴拉契亚圣地测量的吸湿性气溶胶减少。吸湿性较小的颗粒反过来又导致了较低的ALWC.3。在过去十年中，不断变化的气溶胶成分、吸湿性和精细模式颗粒大小正在以不同的过饱和值降低阿巴拉契亚圣地的CCN浓度。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。

Atmospheric aerosols are ubiquitous particles in the atmosphere that are made up of dust, soot, pollution, or even natural emissions from trees. Aerosols are crucially important for weather and climate because they scatter sunlight and act as the base for developing cloud droplets. This award will provide funding for a team of researchers from Appalachian State University and Georgia Tech to study the growth of particles with increasing humidity, and the range of particle sizes that serve as the base for cloud droplets. Aerosol impacts on climate have been highlighted in the Intergovernmental Panel on Climate Change (IPCC) reports as a key uncertainty for climate projections. The project has significant educational and training benefits, with plans for 8-12 undergraduate and Master’s level students to be involved in the project. Appalachian State is a primarily undergraduate university and will benefit from collaboration with a research-intensive institution. The overarching scientific objective of this award is to train, evaluate, and apply measurement-trained models for calculating aerosol liquid water content (ALWC) and cloud condensation nuclei (CCN) spectra at an aerosol network site at Appalachian State University, in Boone, North Carolina. ALWC cannot be directly measured, but it can be estimated from more commonly-measured aerosol optical properties. Intensive field campaigns during the winter and summer of 2024 would provide the necessary data to develop, train, and evaluate machine learning models that would be used to calculate ALWC and CCN spectra. Those models would then be retrospectively applied to the historical database of measurements at Appalachian St. to examine how and why aerosol hygroscopicity, ALWC and CCN spectra are changing. More specifically, the researchers will test the following hypotheses:1. Machine learning models such as Random Forest, when trained using regionally-representative particle number size distributions and aerosol optical properties, are capable of predicting ALWC and CCN spectra at the Appalachian St. site;2. Changing aerosol composition in the Southeastern US is leading to less hygroscopic aerosols measured at Appalachian St. over recent years. Less hygroscopic particles in turn are leading to lower ALWC.3. Changing aerosol composition, hygroscopicity, and fine-mode particle size over the last decade are reducing the CCN concentrations at the Appalachian St. site at different supersaturation values.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.