Results from Continuous Atmospheric Boundary Layer Humidity Profiling with a Compact DIAL Instrument

Continuous or quasi-continuous boundary layer water vapor profiling is widely held to be a major unmet requirement for improving weather analysis and prediction. In this paper, we present recent field campaign results demonstrating the performance of a prototype compact Water Vapor DIAL (DIfferential Absorption Lidar) system incorporating a ceilometer-type telescope design. The instrument uses semiconductor laser sources in the sub-micron wavelength region and is designed to continuously report water vapor mixing ratio profiles in unattended all-weather operation. Extensive comparison campaigns have been carried out in co-operation with the University of Hohenheim, Germany, the Finnish Meteorological Institute FMI, and the German National Meteorological Service, the Deutscher Wetterdienst (DWD). These campaigns included regular radiosonde soundings and established research lidar systems reporting water vapor mixing ratio profiles for comparison purposes. Mean absolute deviation to the DWD Raman lidar (Ramses) was less than 0.3 g/kg within the boundary layer. The DIAL prototype was operated continuously, including periods of precipitation, and gives promise for a rugged and low-cost instrument suitable for unattended 24/7 operational use. The new technology is expected to bring significant improvements to short-term weather forecasts in the future.