Evaluation of an Eye-Safe Differential Absorption Lidar (DIAL) for Water Vapor Profiling in the Lower Troposphere

Improved measurements of water vapor are a long-standing observational challenge to the meteorological and climate research and forecasting communities. In an effort to obtain continuous, long-term, high-resolution water vapor and aerosol profiles in the lower troposphere, an eye-safe, all semiconductor-based, micro-pulse differential absorption lidar (DIAL) instrument has been developed at Montana State University. The water vapor profiles with 150-m vertical resolution are averaged for 15 minutes. Aerosol profiles are retrieved with 1-minute temporal averaging. A collaboration with NCAR has been established to improve performance and field harden the DIAL instrument to allow for autonomous observations. This technology potentially fills a national long-term observing facility gap.

Multi-week field tests of the DIAL instrument at multiple sites were performed during the summer and fall of 2012. Supplementary datasets for intercomparisons and validation include radiosondes, microwave radiometer profilers and Raman lidars. WSR-88D radar data and satellite imagery will be used to characterize the larger-scale conditions during the DIAL observations. Instrument reliability, uncertainty, systematic biases, detection height statistics and environmental complications will be evaluated. Performance will be judged in the context of diverse scientific applications ranging from operational weather prediction and seasonal climate variability to more demanding climate system process studies at the land-canopy-ABL interface. Our primary objective is to estimate the extent to which such research and operational applications can be satisfied with a low-cost autonomous network of similar instruments.