Micro-Pulse DIAL for Atmospheric Water Vapor Profiling

Water vapor plays a key role in Earth’s climate and weather patterns. Accurate, high resolution measurements of the water vapor vertical profiles in a region have been found to significantly improve the numerical weather prediction models’ short-term forecasts, precipitation forecasts, as well as severe weather forecasts. However, current measurement techniques provide very coarse resolution in space, time, and/or altitude. A network of continuously sampling water vapor profilers would greatly expand the scientific knowledge of the atmosphere and serve as a valuable input into numerical weather models. This would be of interest not only to the Department of Energy’s Environmental Sciences Division but to other institutions such as the National Weather Service, the National Center for Atmospheric Research, the Federal Emergency Management Agency, and the military. Differential absorption lidar has the potential to greatly improve the resolution and accuracy of atmospheric water vapor measurements when integrated into a global network, but, while there are some research-grade systems, there doesn’t exist a commercial one with the potential for deployment into a sensing network. One promising research-grade lidar system is based on two narrow-linewidth amplified laser-diodes micro- pulsed at high repetition rates with state-of-the-art optical filtering in the photon-counting receivers. This instrument has already demonstrated strong performance in field campaigns over the last 5 years. The overall goal of this SBIR work is to transition this sensor from its current state as a mobile laboratory to a streamlined instrument commercially available for widespread deployment. Such a system promises to provide continuous monitoring of water vapor vertical profiles in an autonomous, eye-safe instrument that can be deployed in a network of sensors at relatively low cost and requiring minimal maintenance. The Phase I work was focused on developing several upgrades to the transmitter subsystem of the lidar instrument. These upgrades were designed to reduce the system size and, more importantly, its cost and complexity without sacrificing any performance. The laser control and wavelength locking electronics were all consolidated onto a single board and all the transmitter optics were fiber coupled to eliminate drift due to misalignment. In this Phase II project, the recently developed upgrades will be incorporated into the main lidar system for validation and long-term, autonomous testing. To ensure autonomous field operation extra remote control and monitor functionality will be added, including a robust software package and communication library. An improved instrument will be constructed and tested both in controlled laboratory conditions and a mission relevant field campaign. A streamlined prototype system will be developed for beta testing with early adopters in a follow-on Phase IIB proposal to transition this instrument into a commercial product line.