Effects of Aerosols on Microphysical Properties of Springtime Clouds Containing Ice

冰云在调节气候、产生降水和为化学反应提供场所方面很重要。在大气中，冰的成核主要有两种方式：一种是通过液体液滴的均匀冻结，另一种是通过颗粒核上的异质相互作用。均相成核可以从理论上进行预测，而非均相成核要复杂得多。异质冰核可以通过几种机制启动冰的形成，包括沉积、接触、浸泡和凝结。在大气中的各种条件下，作为冰核的粒子的类型和数量被描述得非常糟糕。人类活动对颗粒负荷的变化，无论是直接排放，还是通过土地利用和降水的变化，都可能影响冰和混合相云的特征。然而，在我们了解冰层形成的物理机制之前，无法准确预测这些对冰云的“气溶胶间接效应”。先前的测量提供了一个开始，但还需要更多的信息。对冰核作用的进一步理解需要结合现场实验、实验室研究和模型。首席调查员将采用一种直接撞击和蒸发冰晶的实验方法，以评估其非挥发核的性质。这些信息将与其他研究人员的一系列免费测量结果相结合。这项工作的主要目的是为了更好地理解相对简单的云中冰成核--层中冰--L实验。将使用建模计算和现场测量来研究与从飞机上采集冰块相关的问题，以及它们对收集的数据的潜在影响。这将增加基本冰核研究的学术价值。这项工作有几个方面对更广泛的社区很重要。首先，最重要的是了解人类活动产生的气溶胶(无论是直接或间接通过土地利用的变化)如何影响降水发展和云对地球气候的辐射影响。第二，对人力资源有积极影响。ICE-L实验计划增加一个强大的教育部分，新技术允许实时数据整合到大学气象学课程中。此外，一名本科生和研究生将与PI和同事一起分析和解释收集的数据。此外，该项目将在许多其他实验中提高对飞机冰样及其对过去和未来测量的影响的理解。

Ice clouds are important in regulating climate, in producing precipitation, and in providing sites for chemical reactions. Ice nucleation occurs in the atmosphere in two primary ways: through homogeneous freezing of liquid solution droplets and through heterogeneous interaction on a particulate nucleus. Homogeneous ice nucleation can be predicted by theory, while heterogeneous ice nucleation is much more complex. There are several mechanisms by which a heterogeneous ice nucleus may initiate ice formation, including deposition, contact, immersion, and condensation. The types and numbers of particles that act as ice nuclei under various conditions in the atmosphere are very poorly characterized. Changes to particulate loadings by anthropogenic activity, whether direct emissions or through land-use and precipitation changes, are likely to influence characteristics of ice and mixed-phase clouds. However, these "aerosol indirect effects" on ice clouds cannot be accurately predicted until we understand the physics of ice formation. Prior measurements provide a beginning, but much more information is needed. Further comprehension of ice nucleation will require a combination of field experiments, laboratory studies, and modeling. The Principal Investigator will undertake an experimental approach involving direct impaction and evaporation of ice crystals to evaluate the properties of their non-volatile nuclei. This information will be integrated with that from a series of complimentary measurements by other investigators. The primary objective in this work is to better understand ice nucleation in relatively simple clouds in the Ice in Clouds--Layer (ICE-L) experiment. Problems associated with sampling ice from aircraft, and their potential influence on collected data, will be studied using modeling calculations and field measurements. This will add to the intellectual merit of the basic ice nucleation studies. There are several aspects of this work that are important to the broader community. First, there is the primary importance of understanding how aerosol production due to human activity (whether directly or indirectly through land-use changes) influences precipitation development and the radiative impact of clouds on the earth's climate. Second, there is the positive impact on human resources. A strong educational component is planned for the ICE-L experiment, with new technology allowing real-time data to be integrated into university meteorology classes. Additionally, an undergraduate student and graduate students will work with the PI and colleagues to analyze and interpret the data collected. Additionally, this project will yield improved understanding of ice sampling by aircraft and its implications for past and future measurements in numerous other experiments.