The Impact of Fire on Entrainment and Precipitation Efficiency Derived from Isotope Ratios

非洲中部和南部的生物质燃烧产生了世界上最密集的烟雾层。烟羽飘过南大西洋，在那里与大面积的低空层积云汇合。尽管这些类型的云在当地和全球气候中扮演着不成比例的重要角色，但人们对烟雾气溶胶颗粒和层积云如何相互作用的细节还没有充分了解。该项目旨在提高对烟雾如何改变云附近空气循环方式的理解，污染云中的云滴与原始云中的云滴如何以不同的速率蒸发，以及当烟雾存在时如何改变毛毛雨。将从飞越纳米比亚附近的烟雾和云层的飞机上测量水蒸气和云液中氧和氢的稳定同位素比率，以评估大气混合、云蒸发和形成雨的云滴的比例的特征。这些特征很难用更传统的方法来量化。同位素数据将用于评估NCAR社区地球系统模型模拟的携带和蒸发，以评估从实验中获得的新认识可以改进模型模拟的地方。由于缺乏云-烟相互作用的知识，导致气候模式对过程的处理粗糙，从而导致气候模式模拟中存在重要的未解决的不确定性。同位素研究提供了一种迫切需要的关键检查，以了解云是如何在模型中被描述的，并就哪些机制被错误地表示提供了具体的指导。收集的数据集使几个研究小组能够使用同位素约束来测试和比较他们的模型，这将成为该实验的宝贵遗产。数据模型综合促进了观察和建模专家之间的协作，并使学生能够结合建模和数据方法方面的专业知识进行培训，从而通过综合获得增强的知识。该项目通过将研究经验纳入俄勒冈州立大学的课堂教学和公共宣传论坛，为参与多个层次的学习提供了机会。

Biomass burning in central and southern Africa produces some of the world's most dense layers of smoke. The smoke plumes and transported over the southern Atlantic Ocean where they merge with wide areas of low altitude stratocumulus clouds. The details of how smoke aerosol particles and stratocumulus clouds interact is inadequately understood, despite the disproportionally large role those types of clouds play in local and global climate. This project seeks to improve understanding of how smoke changes the way air circulates near clouds, how cloud droplets in polluted clouds evaporate at different rates from those in pristine clouds, and how drizzle is modified when smoke is present. Stable isotope ratios of oxygen and hydrogen in water vapor and cloud liquid will be measured from aircraft flights though smoke and cloud layers near Namibia to evaluate characteristics of atmospheric mixing, cloud evaporation and the fraction of clouds droplets which grow to produce rain. These characteristics are difficult to quantify from more traditional methods. Isotopic data will be used to evaluate entrainment and evaporation simulated by the NCAR Community Earth System Model to evaluate where new understanding from the experiment can improve model simulations. Lack of knowledge about cloud-smoke interactions leads to crude treatment of processes in climate models, which consequently leads important unresolved uncertainties in climate model simulations. The isotopic study provides a sorely needed critical check on how clouds are depicted in models and gives specific guidance as to which mechanisms are incorrectly represented. The datasets collected enable several research groups to test and compare their models using isotopic constraints which will serve as a valuable legacy of the experiment. The data-model synthesis fosters collaboration that bridges between observation and modeling specialists and enables students training in combining expertise in modeling and data methods to achieve enhanced knowledge though synthesis. The project provides opportunities to engage learning at many levels though incorporation of research experiences in class room teaching at Oregon State University and in public outreach forums.