Two-component Winds from Eye-safe Elastic LIDAR and Optical Flow above the Reach of Most Towers

为了推进大气科学和相关应用的研究，需要改进对10平方公里或更大范围内低空气流的详细空间结构的观测，并延长观测时间。 该项目将开发和评估一个地基、扫描、人眼安全的弹性后向散射激光雷达（光探测和测距）观测系统的能力，该系统与两个候选数值运动估计算法相结合，以确定典型便携式气象塔（即，高度为50-150米AGL）在光学清晰的大气中，并在几个月的时间。 该项目将利用NSF开发的资产，即可移动的拉曼移位人眼安全气溶胶激光雷达（真实的）作为弹性后向散射激光雷达。 将摄取图像型激光雷达数据的两种数值风反演技术是现有的“互相关”方法以及基于小波的“光流”方法。 后者最近由法国合作者开发。 这两种技术都将通过优化软件来实现，以利用图形处理单元的大规模并行但紧凑，节能和负担得起的功能。 这将大大增强弹性激光雷达系统，使其能够实时进行风场观测。 这两种模式的气流估计将与独立的风测量从一个小的，眼睛安全的多普勒激光雷达在相同的红外波长的弹性激光雷达。 该项目的智力价值集中在开发和评价用于检索小尺度边界层流动特征的结构和演变的改进和可靠的手段。 这一努力的更广泛影响将包括加强合作，对产生的流场进行关键表征，并利用流场促进对边界层过程的理解（例如，稳定的夜间边界层中的气流），以及加强本科教育，涉及来自各种专业的学生，他们将被分配到紧密关注的任务，以支持该项目的既定目标。 将为一名研究生提供实践培训，并为一名博士后研究助理提供指导，以确保取得成功。 研究结果将通过同行评审文献以及国内和国际会议加以传播。

Improved observations of the detailed spatial structure of low-level airflow over areas on the order of ten square kilometers or more and for extended time periods are needed to advance research in the atmospheric sciences and related applications. This project will develop and evaluate the ability of a ground-based, scanning, eye-safe elastic backscatter LIDAR (LIght Detection And Ranging) observing system coupled with two candidate numerical motion estimation algorithms to determine vector wind fields above the reach of typical portable meteorological towers (i.e., heights of 50-150 m AGL) in the optically-clear atmosphere and over periods of several months. The project will utilize an NSF-developed asset, the transportable Raman-shifted Eye-safe Aerosol Lidar (REAL), as the elastic backscatter lidar. The two numerical wind retrieval techniques that will ingest image-type lidar data are an existing "cross-correlation" method as well as a wavelet-based "optical flow" approach. The latter has been recently developed by French collaborators. Both techniques will be implemented via software optimized to take advantage of the massively parallel yet compact, energy efficient, and affordable power of graphical processing units. This will result in a significant enhancement of the elastic lidar system by enabling it to produce wind-field observations in real-time. Both modes of airflow estimation will be compared with independent wind measurements from a small, eye-safe Doppler lidar operating at the same infrared wavelength as the elastic lidar. The Intellectual Merit of this project centers on the development and evaluation of improved and reliable means for retrieving the structure and evolution of small-scale boundary layer flow features. Broader Impacts of this effort will include strengthened collaborations for critical characterization of the resulting flow fields and use of the flow fields to advance understanding of boundary layer processes (e.g., airflow in stable nocturnal boundary layers) as well as enhanced undergraduate education involving students drawn from a wide variety of majors, who will be assigned to tightly-focused tasks in support of this project's stated goals. Hands-on training for a graduate-student and mentorship of a post-doctoral research associate will be provided to ensure successful outcomes. Results will be disseminated via peer-reviewed literature and a combination of domestic and international conferences.