New Studies Linking Ice Nucleation and Precipitation

降水是地球上唯一最重要的淡水生成来源，但我们在微物理层面上对其形成和演变的过程水平的理解是粗略的，并且仍然非常不确定。 特别是，冰的微物理过程的相对作用，从冰的启动和增长，冰分裂的约束。 本研究的目的是应用一种新的方法，测量单个雨和毛毛雨滴的冻结行为，其目的是参数化雨率的敏感性冰核数concentration.INTELLECTUAL MERIT降水形成时，滴碰撞和合并，迅速分流云水到毛毛雨和雨。 为了启动这个过程，必须存在少量较大的水凝物，通常假设它们是云中的冰晶，这些冰晶足够冷，可以发生异质冰成核。 每个降水粒子都含有这种种子，只要没有发生冰增殖或水滴破碎等次级过程。为了分析初级和次级过程的相对重要性，将在液氮中收集单个雨滴并储存在石蜡中。 每个雨滴将被放置在一个寒冷的阶段，它冻结的温度将被测量。 对流风暴、天气尺度冬季风暴、锋面通道和热带气旋残留降水的雨滴冻结温度分布将作为降水系统演变的函数进行分析。 所有的数据将在更大的气象和微物理背景下进行分析，即降雨率，云顶温度，云滴数浓度，并用于限制降水的敏感性，冰成核列入数值天气和气候预报models. broaderimpactsThe调查，虽然在性质上是基本的，触及的问题具有重要的社会影响。据推测，来自人类活动的气溶胶影响冰的过程，并反过来修改降水。令人惊讶的是，尽管它对社会具有根本的重要性，而且在本杰明·富兰克林之后200多年？虽然我们推测冰的过程与降水的形成有关，但我们仍然不了解所涉及的微物理过程的相对重要性。这里的实验将有助于限制这个问题。 除了典型的传播渠道（会议和同行评议的文献贡献），研究人员将举办公开讲座，让罗利/达勒姆地区的非科学界参与这一主题。北卡罗来纳州的一些本科生和研究生。州立大学将与该项目的首席研究员合作。

Precipitation is the single most important source of freshwater generation on Earth, but our process-level understanding of its formation and evolution at the microphysical level is crude and remains highly uncertain. In particular, the relative roles of ice microphysical processes, from ice initiation and growth to ice splintering are poorly constrained. The goal of this study is to apply a new method that measures the freezing behavior of individual rain and drizzle drops, with the objective to parameterize the susceptibility of rain rate to ice nuclei number concentrations.INTELLECTUAL MERITPrecipitation forms when drops collide and coalesce, rapidly shunting cloud water into drizzle and rain. To initiate this process a small number of larger hydrometeors must be present, usually assumed to be ice crystals in clouds that are cold enough for heterogeneous ice nucleation to occur. Each precipitation particle contains this seed, provided secondary processes such as ice multiplication or drop breakup did not occur. To analyze the relative importance of primary and secondary processes, individual rain drops will be collected in liquid nitrogen and stored in paraffin. Each raindrop will be placed on a cold stage and the temperature at which it freezes will be measured. The distribution of raindrop freezing temperatures for precipitation from convective storms, synoptic scale winter storms, frontal passages, and remnants of tropical cyclones will be analyzed as a function of the evolution of the precipitating system. All data will be analyzed in the larger meteorological and microphysical context, i.e. rain rate, cloud-top temperature, cloud droplet number concentration, and used to constrain the susceptibility of precipitation to ice nucleation for inclusion in numerical weather and climate prediction models.BROADER IMPACTSThe investigation, although fundamental in nature, touches on questions with important societal implications. It is hypothesized that aerosols from anthropogenic activity affect ice processes and in turn modify precipitation. It is surprising that despite its fundamental importance to society, and more than 200 years after Benjamin Franklins? conjecture implicating ice processes in precipitation formation, we still do not understand the relative importance of the microphysical processes involved. The experiments here will help to constrain this question. In addition to the typical dissemination channels (conferences and peer reviewed contributions to the literature), the investigators will host public lectures to engage the non-science community in the Raleigh/Durham area with this topic. A number of undergraduate and graduate students at N.C. State University will work with the principal investigator on this project.