Wind tunnel investigations on riming of ice particles: Retention of water-soluble organics and the influence of turbulence on the growth of graupels.

冰粒边缘的风洞研究：水溶性有机物的保留和湍流对霰粒生长的影响。

• 批准号: 174758764
• 负责人: Dr. Subir Kumar Mitra
• 金额: --
• 依托单位: Institut für Physik der Atmosphäre
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/174758764?language=en
• 关键词: Wind; tunnel; investigations; riming; ice

In recent years, gaseous and particulate organic species in the atmosphere have received increased attention. Organic compounds are found in cloud and rain water as well as in snow samples. However, the removal processes underlying their scavenging is not adequately enough understood such that these are amenable for integration in numerical models. One possibility via the ice phase would be the retention of organics during riming, i.e. the deposi-tion of super-cooled water droplets on ice particles. During this process, the organic species (or fractions of their amounts) can be transferred into and retained by the ice phase while another fraction is released back into the gas phase. These fractions will be investigated and quantified in wind tunnel experiments where freely floating ice particles and snow flakes are exposed to clouds of supercooled droplets containing organic substances of atmospheric significance. As the most abundant water-soluble organics in cloud water are carboxylic ac-ids and aldehydes the proposed experiments mainly extend over these groups. Another topic of great interest is the influence of turbulence on microphysical processes. The collisional growth of cloud droplets is significantly enhanced by turbulence; therefore, similar results are expected in the case of riming as an analogous process in the ice phase. The determination of the growth rate of ice particles by riming under turbulent conditions is necessary for the – so far not yet available - formulation of more realistic collection kernels (in comparison to the laminar case) for the modeling of cloud physics and chemistry.

近年来，大气中的气态和颗粒态有机物种受到越来越多的关注。在云和雨水中以及雪样中都发现了有机化合物。然而，对其清除过程的了解还不够充分，以致于这些过程可以整合到数值模式中。通过冰相的一种可能性是在沸腾过程中有机物的保留，即过冷水滴沉积在冰粒上。在这个过程中，有机物质(或其数量的一小部分)可以转移到冰相中并被冰相保留，而另一种物质被释放回气相。这些组分将在风洞实验中进行研究和量化，在风洞实验中，自由漂浮的冰粒和雪花暴露在含有具有大气意义的有机物质的过冷液滴云中。由于云水中最丰富的水溶性有机物是羧酸和醛，因此本实验主要涉及这些基团。另一个令人非常感兴趣的话题是湍流对微物理过程的影响。湍流显著地促进了云滴的碰撞增长；因此，在冰相中的结冰过程中，预计也会有类似的结果。在湍流条件下通过翻转来确定冰粒的生长速度，对于(与层流情况相比)建立更真实的云层物理和化学模型的收集核是必要的--到目前为止还没有。