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.
