Continuation of Rain In Cumulus over the Ocean (RICO) Data Analysis

该项目是首席研究员2005年参加加勒比区域海洋积云雨云场研究的结果。这是对RICO现场数据分析的延续。在这些云中，导致降水的水滴的聚结和收集取决于几个关键的物理过程，包括空气中云凝结核（CCN）的特性;热量、水汽、颗粒和气体的表面通量;温度、湿度和风的垂直廓线;云的几何形状;以及夹带和混合。到目前为止，分析的重点是后者及其对云滴光谱的影响。在这里，来自国家大气研究中心C-130研究飞机上的粒子体积监测器（PVM）云探测器的观测结果被用来为这种混合是如何发生的提供证据。它是RICO期间使用的唯一微物理探测器，具有足够大的敏感体积，可以为小至10厘米的云尺度提供可用的采样统计数据。基于对RICO研究飞行12号上采集的几十个云的分析的主要发现包括夹带到采样云中的无液滴环境空气包大小的概率密度函数。这些包裹比迄今为止建议的要小得多，观测结果表明，injurious型混合过程占主导地位的外部空气夹带到这些cloud. Effort的这项研究将扩展高分辨率的数据分析使用PVM和其他C-130数据的其他RICO航班有更少的垂直风切变和更大量的降水滴比发现的航班12。这将有助于回答这样一个问题：到目前为止，我们的结果是否只适用于产生12号航班上取样的云的条件，或者它们是否也适用于在不同条件下形成的积云？同样类型的分析也将扩展到1995年佛罗里达积云研究中使用相同PVM仪器进行的观测。这些佛罗里达云比典型的RICO贸易风积云更强大，并允许另一个测试RICO结果可以推广的程度。此外，首席研究员将继续与犹他州大学的研究人员合作，并努力建立一个详细的夹带和混合的数值模型，该模型将显式微观物理和湍流耗散的相互作用扩展到Kolmogorov尺度。这里，PVM高速数据可以用作约束，也可以用作输入。还计划与沙漠研究所的研究人员及其对云凝结核的RICO测量进行进一步合作，以估计Flight 12积云的过饱和度。最后，首席研究员与几位RICO模型师合作，根据他对12号航班上观测到的云的详细分析，对该航班上遇到的条件下云的发展进行了数值大涡模拟。这项工作的智力价值在于其对解决外部空气夹带到云中后如何发生混合的关键问题的贡献。这一问题已经辩论了多年，但没有达成一项决议。处理这个问题的最新文献强调了理解这一过程的重要性，因为它对液滴光谱、聚结和云光学有很强的影响。这项工作利用了一个优秀的和独特的数据集，从RICO现场研究，以澄清这一问题。这项工作的更广泛的影响是它有助于更定量地了解液滴光谱演变和积云降水的形成。这种理解需要改进，并用于改进云模型，以便更准确地预测云在我们气候系统中的作用。犹他州大学和内华达州沙漠研究所的研究生研究也将通过与首席研究员的合作得到加强。

This project results from the principal investigator's participation in the Rain in Cumulus over the Ocean (RICO) cloud field study in the Caribbean region in 2005. It is a continuation of analysis of RICO field data. The coalescence and collection of drops leading to precipitation in these clouds depends on several key physical processes including characteristics of cloud condensation nuclei (CCN) in the air; surface fluxes of heat, water vapor, particles and gases; vertical profiles of temperature, humidity, and winds; cloud geometry; and entrainment and mixing. The analysis to date has focused on the latter and its effect on the cloud droplet spectrum. Here observations from the particle volume monitor (PVM) cloud probe on the National Center for Atmospheric Research C-130 research aircraft were used to provide evidence for how this mixing occurs. It is the only microphysics probe used during RICO that has a sufficiently large sensitive volume to give useable sampling statistics for cloud scales as small as 10 cm. Key findings based on analysis of several dozen clouds sampled on RICO Research Flight 12 include probability density functions of sizes of droplet-free environmental air parcels entrained into the sampled clouds. These parcels were much smaller than hitherto suggested, and the observations indicate that inhomogeneous-type mixing process dominate following entrainment of outside air into these clouds.The effort of this research will be to extend high resolution data analysis using the PVM and other C-130 data to other RICO flights which have less vertical wind shear and greater amounts of precipitation drops than found for Flight 12. This will help answer the question: are our results to date peculiar for conditions producing the clouds sampled on Flight 12, or are they also applicable to cumuli formed under different conditions? This same type of analysis also will be extended to observations with the same PVM instrument obtained in a 1995 study of Florida cumulus clouds. These Florida clouds were much more robust than the typical RICO trade-wind cumuli and allow another test of the degree to which RICO results can be generalized. In addition the principal investigator will continue collaboration with researchers at the University of Utah and their efforts with a detailed numerical model of entrainment and mixing that extends the interaction of explicit microphysics and turbulent dissipation to the Kolmogorov scale. Here the PVM high speed data can serve as a constraint and also as an input. Further collaboration is also planned with researchers at the Desert Research Institute and their RICO measurements of CCN for the purpose of estimating supersaturations in the Flight 12 cumuli. And finally, the principal investigator collaborate with several RICO modelers performing a numerical large-eddy simulation of clouds developing in conditions encountered on Flight 12, based on his detailed analysis of clouds observed on that flight.The intellectual merit of the work is its contribution towards resolving the critical issue of how mixing occurs following entrainment of outside air into clouds. This has been debated for many years without reaching a resolution. The most recent literature dealing with this issue emphasizes the importance of understanding this process given its strong effect on the droplet spectra, coalescence, and cloud optics. The work takes advantage of an excellent and unique data set from the RICO field study to clarify this issue. The broader impact of the work is its contribution to more quantitative understanding of droplet spectral evolution and the formation of precipitation in cumulus clouds. This understanding needs to be improved and used to improve cloud models so that they can predict the role of clouds in our climate system more accurately. Graduate student research at the University of Utah and Nevada's Desert Research Institute will also be strengthened through collaboration with the principal investigator.