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

大气中冰的辐射和电特性的实验室和现场研究

• 批准号: 9413437
• 负责人: John Hallett
• 金额: $ 79.66万
• 依托单位: Nevada System of Higher Education, Desert Research Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-11-15 至 1999-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9413437&HistoricalAwards=false
• 关键词: Laboratory; Field; Study; Radiative; Electrical

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.

冰晶的实验室研究将包括它们的辐射特性，特别是热红外（2-18 m）消光和发射率。这将包括由局部电场取向的晶体。通过多次路径遍历可以获得测量所需的足够消光。发射率将通过与云层温度以上和低于云层温度的背景进行比较得到。光学深度测量将在685 nm进行，为归一化红外消光和吸收光学深度测量提供一个方便的综合云投影面积测量。消光测量将考虑比以前产生的尺寸和习惯光谱更窄的云，利用拉梅尔发生器的原理（在特定温度下控制成核，然后控制生长）。液滴成核模式将控制结晶度（每个核的晶体数量），这将与CCN的性质（大小，组成）有关。作为本研究的补充，我们将研究在卷云温度下，微量杂质缺陷在导致冰晶习惯变化中的作用。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方案。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，空心柱，等轴晶体和杂质（HNO3））。这些研究将通过在几个项目（TOGA-COARE， EUCREX, FIRE II WISP）的高空飞行中收集的数据与大气进行比较，这些项目在已知条件下收集了晶体。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有关，从而与晶体浓度和形态有关。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，并用作开发数值/分析模型的基准。来自这些不同方法的想法将被综合起来理解卷云的形成及其可能的辐射特性。热带卷云起源于具有相关电活动的深层对流。这种冰和电活动的起源（作为高空冰产生和低层地面降水的替代）将通过NOAA P3在CAPE、几次飓风和热带对流上已经获得的数据进行调查。这将把冰的演化机制与低层云的聚结过程、过渡区二次冰产生的速度以及最终冰水物质进入铁砧的可能通量联系起来，从而在高空产生不同的辐射特性。