The atmospheric sciences research and forecasting communities have a clearly-stated need to obtain improved measurements of water vapor. Montana State University (MSU) has pioneered an alternative low-cost active remote sensing capability which has the potential to help fill the observational gap for range resolved measurements of atmospheric water vapor. This technology employs the well-known differential absorption lidar (DIAL) technique and uses diode-laser- based technologies for the transmitter which significantly reduces the initial and operational costs. Since June of 2011, MSU and the National Center for Atmospheric Research (NCAR) have worked together to expand and evaluate the capability of this new technique. In 2012 the MSU prototype water vapor DIAL was modified to allow for unattended operations with a completely eye-safe beam. The modified instrument was field tested over a wide range of atmospheric conditions alongside other instrumentation to evaluate its performance. The evaluation indicated that the technology was well-suited for autonomous, long-term measurement of water vapor over a wide range of concentrations and atmospheric conditions. However, significant engineering modifications were required to make the instrument capabilities useful for the atmospheric science community. The revised design, now being constructed and tested, will be discussed. It should allow measurements closer to ground level, improve performance in the presence of clouds and during daytime, and improve the system's stability and reliability. Furthermore, the prototype instrument would have the potential to form the basis of a ground-based network of eye-safe autonomous instruments.
Continuous Water Vapor Profiling with a diode-laser-based Differential Absorption Lidar (DIAL)