CAREER: Size Resolved Measurement of Cloud Condensation Nuclei Concentration and Properties

职业：云凝结核浓度和性质的尺寸分辨测量

• 批准号: 0094342
• 负责人: Don Collins
• 金额: $ 50.66万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0094342&HistoricalAwards=false
• 关键词: CAREER; Size; Resolved; Measurement; Cloud

This grant supports the design and fabrication of a novel instrument for studying the atmospheric aerosols that serve as condensation nuclei for the formation of cloud droplets. The instrument consists of a differential mobility analyzer (DMA), which separates the aerosol particles into a narrow range of sizes, followed by a cloud condensation nucleus separator (CCNS), which separates the more hygroscopic particles from the less hygroscopic ones. It is the hygroscopic particles that can serve as condensation nuclei. The CCNS consists of two concentric cylinders, between which an electric field is applied. The annular region between the cylinders is basically a thermal gradient diffusion chamber. The inner and outer walls are maintained at different temperatures and at water saturation by means of wet filter paper, so that the space between them is supersaturated. The particles are charged when they leave the DMA, and the field applied to the CCNS causes them to migrate slowly towards the inner wall as they move with the air through the chamber. The electrical mobility of the particles is reduced as they grow by condensation. Hence the particles that grow large have less chance of migrating to the inner wall than those that remain small. From the initial population of near-equal sized particles that enter the CCNS, the less hygroscopic ones are thus deposited on the inner wall, and those that serve as CCN at the applied supersaturation pass through. The two-stage instrument therefore makes it possible to study the nucleating properties of aerosol particles in different size ranges. As a further step in the analysis, the chemical composition of the CCN that exit the instrument may be determined using a single-particle mass spectrometer. Results of the research are relevant to the basic physics of cloud formation and to the question of aerosol effects on the solar reflectivity of clouds.The educational component of this CAREER award consists of a summer course for undergraduate students on techniques, applications, and practical aspects of meteorological and atmospheric chemical measurements. The culmination of the course is a week-long field campaign in Marina, CA, centered on airborne observations with the research facilities of the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS).

该拨款支持设计和制造一种新型仪器，用于研究大气气溶胶，这些气溶胶充当云滴形成的凝结核。 该仪器包括一个微分迁移率分析仪（DMA），它将气溶胶颗粒分离成一个狭窄的尺寸范围，然后是一个云凝结核分离器（CCNS），它将吸湿性较强的颗粒与吸湿性较低的颗粒分离开来。 吸湿粒子可以作为凝结核。 CCNS由两个同心圆柱体组成，在两个圆柱体之间施加电场。 圆柱体之间的环形区域基本上是一个热梯度扩散室。 内壁和外壁通过湿滤纸保持在不同的温度和水饱和度下，使得它们之间的空间过饱和。 当颗粒离开DMA时，它们是带电的，并且当它们随着空气移动通过腔室时，施加到CCNS的场使它们缓慢地朝向内壁迁移。 粒子的电迁移率随着它们通过冷凝而生长而降低。 因此，长大的颗粒比那些保持小的颗粒迁移到内壁的机会更少。 从进入CCNS的几乎相等尺寸的颗粒的初始群体，吸湿性较低的颗粒因此沉积在内壁上，并且在所施加的过饱和度下充当CCN的那些颗粒通过。 因此，两级仪器使得研究不同尺寸范围内的气溶胶颗粒的成核特性成为可能。作为分析中的进一步步骤，可以使用单粒子质谱仪来确定离开仪器的CCN的化学组成。 研究结果与云形成的基本物理学和气溶胶对云的太阳反射率的影响问题有关。该CAREER奖的教育部分包括为本科生开设的关于气象和大气化学测量的技术、应用和实践方面的暑期课程。 该课程的高潮是在加利福尼亚州玛丽娜为期一周的实地活动，以跨学科遥控飞机研究中心（CIRPAS）的研究设施为中心进行空中观测。