Collaborative Research: Development of a Phase Doppler Interferometer for Characterization of Particle-Turbulence Interactions in Clouds

这笔赠款支持开发相位多普勒干涉仪(PDI)，以观测细尺度湍流与云中液滴的相互作用。科学目标是评估湍流对碰撞和合并的影响程度，即云滴相互作用并产生雨的过程。相位多普勒干涉术是一种光学技术，用于测量由两束激光相交定义的小体积中单个颗粒的大小，以及颗粒相对于仪器的速度。PI将与加州大学圣克鲁斯分校的Patrick Chuang博士和Artium Technologies的William Bachalo博士合作，设计和制造一种特别适合测量云滴的PDI。该计划是开发一种仪器，能够测量直径在2到200微米之间的液滴的大小、速度和间距。将特别注意光学检测设备的常见问题，如符合误差和采样体积与液滴大小的关系。利用现有的风洞和云室在实验室条件下测试该仪器，将是验证其性能的重要部分。尽管最终目标是将PDI安装在飞机上进行云内测量，但调查人员将在实验室云上进行初步实验，并在塔楼或悬挂在系留气球上的现场部署中进行初步实验。长期以来，人们一直在猜测湍流对降雨产生的碰撞-合并过程可能产生的影响。该仪器将通过在与这一过程有关的小尺度上实际观测云滴的湍流运动，填补知识上的一个重要空白。

This grant supports the development of a phase Doppler interferometer (PDI) to observe the interaction of fine-scale turbulence and droplets in clouds. The scientific goal is to evaluate the extent to which turbulence influences collisions and coalescence, the processes whereby cloud droplets can interact with each other and grow to produce rain. Phase Doppler interferometry is an optical technique for measuring both the size of individual particles in the small volume defined by the intersection of two laser beams and the velocity of the particles relative to the instrument. The PI will work with Dr. Patrick Chuang of the University of California-Santa Cruz and Dr. William Bachalo of Artium Technologies to design and build a PDI especially suited for measuring cloud droplets. The plan is to develop an instrument capable of measuring the size, velocity, and spacing between droplets with diameters between 2 and 200 micrometers. Special attention will be given to problems common to optical detection devices, such as coincidence errors and the dependence of the volume sampled on the drop size. Testing the instrument in laboratory conditions, using existing wind tunnels and cloud chambers, will be an important part of validating its performance. Although the ultimate goal is to mount the PDI in an airplane for in-cloud measurements, the investigators will carry out initial experiments on laboratory clouds and in field deployments on towers or suspended from tethered balloons. There has long been speculation about the possible effects of turbulence on the collision-coalescence process of rain production. This instrument will fill an important gap in knowledge by actually observing the turbulent motions of cloud droplets at the small scales relevant for the process.