Collaborative Research: Cloud System Evolution in the Trades

本研究旨在利用美国国家科学基金会/美国国家大气研究中心湾流五号（HIAPER）的观测资料，了解北太平洋信风边界层云、气溶胶和热力学结构的演变。这项工作包括表征北太平洋副热带东风带层积云（Sc）和晴朗天气积云（Cu）体系中的云、降水和气溶胶场，并使用大涡模拟（LES）模式模拟沿采样轨迹的云演变。知识价值：沿着轨迹的这些特征将有助于我们理解和模拟两种对流状态之间的过渡——这是气候系统中的一个关键因素。LES模式已经成为拉格朗日模拟副热带云量转变的有力工具，但很少有好的数据集可以全面测试这些模拟。特别是缺乏对这种转变过程中气溶胶、云滴数浓度和降水耦合演变的充分观测。因此，观测策略将是采样气溶胶、云、降水和边界层性质，从北太平洋上空的过渡区逆风，并在两到四天后重新采样这些地区。这种拉格朗日方法的目的是尽量减少由于气团从较冷的海面温度向较暖的海面温度移动时对流层下层水平平流造成的大尺度强迫的不确定性，从而促进模式模拟和隔离关键的物理过程。观测系统的两个关键部件将是新开发的HIAPER云雷达（HCR）和HIAPER高光谱分辨率激光雷达（HSRL）。HCR将用于提供云和降水特征。当观测非云量时，HSRL将提供云边界和气溶胶特征。飞机上的全套探测器将用于气溶胶、云、降水和湍流特性的现场测量。加州西海岸和夏威夷之间的航班将采用两种运营模式。其中一个将包括从Sc到Cu过渡区上游和下游的边界层上方飞行高度对云和边界层的遥感（测绘）。另一项将涉及在过渡区上游和下游的两三个选定区域的云下层和云层中进行详细的剖面分析，以对气溶胶、云、降水和湍流进行详细的现场测量。在测量腿上，将使用下降式探空仪来获取边界层内外的热力学和风结构。计划在2015年6月至7月期间进行几次飞行序列。在这些飞行中所做的观测将被用来评估水分、干静态能量和质量预算，通过估计这些参数在一次飞行中采样的上游Sc区域和在随后的飞行中采样的下游Cu区域之间的变化。观测结果的综合将为LES研究提供一个观测框架，从而更好地理解行业中云系统的演变。更广泛的影响：该项目将发展观测和分析技术和战略，促进未来任务的发展，旨在研究其他观测平台难以到达的偏远地区的边界层云。开发的数据集将有助于评估卫星检索技术，以及评估应用于广泛尺度（微物理、中尺度、区域和全球）的模式和模式参数化。该项目的教育部分将包括对研究生和本科生进行数据收集过程技术方面的培训、飞行操作以及随后的数据分析，以解决关键科学问题。此外，将把项目的观察结果整合到可用于本科和研究生水平的教学模块中。

This study aims to understand the evolution of the boundary layer cloud, aerosol and thermodynamic structures along trajectories within the north-Pacific trade-winds using observations from the NSF/NCAR Gulfstream V (HIAPER). This effort includes characterization of the cloud, precipitation and aerosol fields in the stratocumulus (Sc) and the fair-weather cumulus (Cu) regimes within the subtropical easterlies over the northern Pacific and the use of Large Eddy Simulation (LES) models to simulate the cloud evolution along the trajectories sampled. Intellectual merit: These characterizations along trajectories will be designed to aid in our understanding and simulation of the transition between the two convective regimes - a critical factor in the climate system. LES models have become a robust tool for Lagrangian simulations of subtropical cloudiness transitions, but there are few good datasets for comprehensively testing these simulations. In particular, adequate observations of the coupled evolution of aerosol, cloud droplet number concentration and precipitation during such transitions are lacked. Thus, the observing strategy will be to sample aerosol, cloud, precipitation, and boundary layer properties upwind from the transition zone over the North Pacific and to resample these areas two and four days later. This Lagrangian approach is designed to minimize uncertainties in the large-scale forcing due to horizontal advection in the lower troposphere as air masses move from colder to warmer sea surface temperatures and thus facilitate model simulations and isolate critical physical processes. Two key elements of the observing system will be a newly developed HIAPER Cloud Radar (HCR) and the HIAPER High Spectral Resolution Lidar (HSRL). The HCR will be used to provide cloud and precipitation characteristics. The HSRL will provide cloud boundaries and aerosol characteristics when viewing non-cloudy volumes. A full suite of probes on the aircraft will be used for in situ measurements of aerosol, cloud, precipitation, and turbulence properties. Two modes of operations will be made on flights between the west coast of California and Hawaii. One will include remote sensing (mapping) of the clouds and boundary layer from flight levels above the boundary layer made upstream and downstream from the Sc to Cu transition zone. The other will involve detailed profiling in the subcloud and cloud layer in two or three selected areas upstream and downstream from the transition zone to make detailed in situ measurements of aerosols, clouds, precipitation, and turbulence. On the surveying legs dropsondes will be used to obtain the thermodynamic and wind structure in and above the boundary layer. Several flight sequences are planned for the June-July 2015 timeframe. The observations made on these flights will be used to evaluate the moisture, dry static energy and mass budgets by estimating the changes in these parameters between the upstream Sc region sampled on one flight and the downstream Cu region sampled on the subsequent flights. The synthesis of the observations will provide an observational framework for LES studies that will provide a better understating of cloud system evolution in the trades. Broader impacts: The project will develop observing and analysis techniques and strategies that will facilitate the development of future missions aimed at studying boundary layer clouds in remote areas that are not easily reached by other observing platforms. The data sets developed will be useful for evaluating satellite retrieval techniques and for evaluating models and model parameterizations applied to a wide range of scales--microphysical, mesoscale, regional, and global. The educational components of this project will include the training of graduate and undergraduate students on the technical aspects of the data collection processes, flight operations, and the subsequent analysis of data to address key science questions. Further, integration of observations from the project into teaching and learning modules that can be used at both the undergraduate and the graduate level will be developed.