A Laboratory and Field Study of the Radiative and Electrical Properties of Ice in the Atmosphere

Hallett/摘要 对冰晶的实验室研究将包括其辐射特性，特别是热红外（2-18米）消光和发射率。 这将包括由局部电场定向的晶体。 通过多路径遍历将获得用于测量的足够消光。 发射率将通过与高于和低于云温度的背景进行比较来获得。 光学深度测量将在685纳米处进行，以方便测量综合云投影面积，使红外消光和吸收光学深度测量标准化。 消光测量将考虑比以前产生的云更窄的尺寸和习惯谱，利用特定温度下的La Mer发生器（受控成核，然后受控生长）的原理。 液滴成核模式将控制结晶度（每个核的晶体数量），这将与CCN性质（尺寸、组成）相关。 作为这项研究的补充，将调查微量杂质缺陷在卷云温度下导致冰晶习性变化的作用。 实验将在现有的扩散室中进行，并将用于改进成核研究中晶体生产的协议。 这将产生与在不同温度下生长的晶体相关的特定晶体形状（薄板、原始柱、中空柱、等轴晶体和杂质（HNO 3）。 这些研究将通过在已知条件下收集晶体的几个项目（TOGA-COARE、EUREX、FIRE II WISP）的高空飞行中已经取得的数据与大气进行比较。 这些将与它们的成核特性（颗粒挥发性和热分馏）CN和物理尺寸与临界过饱和度相关，并且因此与晶体浓度和形态相关。 实验室产生的冰云消光和发射的灵敏度将与晶体习性和尺寸有关，并用作数值/分析模型开发的基准。 从这些不同的方法的想法将被综合在理解卷云的形成和它可能的辐射特性。 热带卷云起源于与电活动相关的深对流。 这种冰和电活动的起源（作为高空冰生成和低层地表降水的替代物）将根据已经在CAPE的NOAA P3上获得的数据，几个飓风和热带对流进行研究。 这将涉及冰的演变机制，在较低的云水平，二次冰生产在过渡区的速度和最终的冰水物质的可能通量到铁砧，给不同的辐射特性高空的合并过程。

Hallett/Abstract A laboratory study of ice crystals will include their radiative properties, especially thermal infra-red (2-18 m) extinction and emissivity. This will include crystals oriented by local electric fields. Sufficient extinction for measurement will be obtained by multiple path traverses. The emissivity will be obtained by comparison with backgrounds above and below cloud temperature. Optical depth measurements are to be performed at 685 nm to provide a convenient measure of integrated cloud projected area for normalizing infrared extinction and absorption optical depth measurements. The extinction measurements will consider clouds with narrower size and habit spectra than previously produced, utilizing the principle of the La Mer generator (controlled nucleation followed by controlled growth) at a specific temperature. The liquid drop nucleation mode will control the crystallinity (number of crystals per nucleus), which will be related to CCN properties (size, composition). Complementary to this study, an investigation will be made of the role of trace impurity defects role in leading to ice crystal habit changes at cirrus temperatures. Experiments will be carried out in an existing diffusion chamber and will be used to refine the protocol for crystal production in the nucleation study. This will give rise to specific crystal shapes associated with crystals growing at different temperature (thin plate, pristine column, hollow columns, equiaxed crystals and impurity (HNO3). These studies will be compared with the atmosphere through data already taken in high level flights in several projects (TOGA-COARE, EUCREX, FIRE II WISP) where crystals have been collected under known conditions. These will be related to their nucleation characterization (particle volatility and thermal fractionation) CN and physical size vs. critical supersaturation and thence to crystal concentration and morphology. The sensitivity of the laboratory prod uced ice cloud extinction and emission will be related to crystal habit and size and used as benchmarks for development of a numerical/analytical model. The ideas from these different approaches will be synthesized in understanding cirrus formation and its likely radiative properties. Tropical cirrus originates in deep convection with associated electrical activity. The origin of such ice and electrical activity (as a surrogate for ice production aloft and lower level surface precipitation) will be investigated from data already obtained on the NOAA P3 in CAPE, several hurricanes and tropical convection. This will relate ice evolution mechanisms to coalescence processes at lower cloud levels, the rapidity of secondary ice production in the transition region and ultimately the likely flux of ice water substance into the anvil to give differing radiative properties aloft.