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

本项目是2005年首席研究员参与加勒比海地区海洋积云雨（RICO）云场研究的结果。它是RICO实地数据分析的延续。雨滴在这些云中汇聚和聚集导致降水取决于几个关键的物理过程，包括空气中云凝结核（CCN）的特征；热、水蒸气、粒子和气体的表面通量；温度、湿度和风的垂直剖面图；云几何;还有娱乐和混合。迄今为止的分析主要集中在后者及其对云滴谱的影响。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期间使用的唯一的微物理探针，具有足够大的敏感体积，可以为小到10厘米的云尺度提供可用的采样统计数据。基于对RICO研究航班12上取样的几十个云的分析，主要发现包括采样云中携带的无液滴环境空气包裹大小的概率密度函数。这些包裹比迄今为止认为的要小得多，观测表明，在外部空气进入这些云后，非均匀型混合过程占主导地位。本研究的目的是将使用PVM和其他C-130数据的高分辨率数据分析扩展到其他RICO航班，这些航班的垂直风切变较少，降水量比12航班大。这将有助于回答以下问题：到目前为止，我们的结果对于产生第12次航班上采样的云的条件是特殊的，还是它们也适用于在不同条件下形成的积云？这种相同类型的分析也将扩展到使用1995年在佛罗里达积云研究中获得的相同的PVM仪器进行观测。这些佛罗里达州的云比典型的RICO信风积云更加强劲，并且可以对RICO结果的推广程度进行另一种测试。此外，首席研究员将继续与犹他大学的研究人员合作，并努力建立一个详细的卷带和混合数值模型，将显式微物理和湍流耗散的相互作用扩展到Kolmogorov尺度。在这里，PVM高速数据既可以作为约束，也可以作为输入。还计划与沙漠研究所的研究人员及其对CCN的RICO测量进行进一步合作，以估计第12次飞行积雨云的过饱和度。最后，首席研究员与几位RICO建模师合作，根据他对飞行中观察到的云的详细分析，对12号航班上遇到的条件下的云发展进行了数值大涡模拟。这项工作的智力价值在于它对解决外部空气进入云层后如何发生混合这一关键问题的贡献。这个问题已经争论了许多年，但没有达成一个解决方案。最近处理这一问题的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。这项工作利用了来自RICO实地研究的优秀而独特的数据集来澄清这一问题。这项工作更广泛的影响在于它有助于更定量地了解积云中液滴光谱的演变和降水的形成。这种认识需要改进，并用于改进云模型，以便它们能够更准确地预测云在气候系统中的作用。通过与首席研究员的合作，犹他州大学和内华达州沙漠研究所的研究生研究也将得到加强。

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.