Studies of Aerosol Scavenging by Ice Particles in Clouds

这项研究的目的是确定 在降雪中沉积的气溶胶和气体是由于液态云 除水的雾凇机制，无论是由雪晶雾凇 或者是高山表面的霜化。 本研究将集中在如何以及在何处的各种痕迹 大气气溶胶的成分分布在 云中的三种水物质成分：冰、液态水 和水蒸气。 结果将使用获得的 在研究中了解云的微物理特性 绝佳的价钱 对冰形成的微物理条件的估计 生长的粒子将由观测到的气象条件制成 以及使用简单的冰晶轨迹和生长模型。 了解发生的大气条件， 对云滴、冰粒和 气溶胶粒子应该允许更好地了解什么是 清除和生长过程导致最终观察到的冰 晶体化学成分 大气化学的关键问题涉及到 空气中的悬浮微粒和气体被云清除 雨，在大地上， 在冷冻状态下 条件下，这些清除的材料中的很大一部分是 沉积在雾凇冰，这是冰的结果，从冻结 在预先形成的雪晶上的过冷雾或云滴 或地球表面的物体上。 清除气溶胶， 据信，在下雪条件下产生的气体主要是 收集成液滴并随后沉积在雾凇中， 而不是在雪晶中 关于以下方面相对重要性的数据： 竞争沉积机制将有助于理解 化学元素在自然界中的全球循环。 在 特别是，这些知识应该有助于了解条件 控制高山酸性物质的沉积 海拔 对森林损害的最高认识 海拔升高引起了人们对是什么机制导致这些问题的质疑。 在地域范围上如此明显地划分影响。 详细 对大气沉积过程的了解应该有助于 酸、氧化剂或其他空气传播成分的作用。

The objective of this research is to determine what fraction of the aerosols and gases deposited in snowfall is due to liquid cloud water removal by the riming mechanism, whether by snow crystal riming or by high mountain-surface riming. This study will focus on how and where the various trace constituents of the atmospheric aerosol are distributed among the three water substance components within the cloud: ice, liquid water and water vapor. The results will be interpreted using acquired knowledge of the microphysical properties of the cloud at the study site. Estimates of the microphysical conditions within which the ice particles grew will be made from observed meteorological conditions and the use of a simple ice crystal trajectory and growth model. Knowledge of the atmospheric conditions which occur and careful on-site characterization of the cloud droplets, ice particles and aerosol particles should permit a better understanding of what scavenging and growth processes lead to the final observed ice crystal chemical composition. Key questions of atmospheric chemistry pertain to the mechanisms by which airborne aerosol particles and gases are scavenged by clouds and rain, and deposited at the earth's surface. Under freezing conditions a significant fraction of these scavenged materials is deposited in rime ice, which is the ice that results from freezing of supercooled fog or cloud droplets either on preformed snow crystals or on objects at the earth's surface. The scavenging of aerosols and gases under snowing conditions is believed to occur predominantly by collection in liquid droplets and subsequent deposition in the rime, rather than in the snow crystals. Data on the relative importance of competing deposition mechanisms will contribute to the understanding of the global cycling of the chemical elements in nature. In particular, this knowledge should help to understand the conditions governing the deposition of acidic materials at high mountain elevations. The recognition of forest damage at the highest elevations has raised questions about what mechanisms cause these effects to be so sharply delimited in areal extent. A detailed understanding of atmospheric deposition processes should help to sort out the roles of acids, oxidants, or other airborne constituents.