Advances in Continuous Atmospheric Boundary Layer Humidity Profiling with a Compact Dial Instrument

Continuous or semi-continuous boundary layer water vapor profiling is one of the major unmet requirements for improving weather analysis and prediction. In this paper we present preliminary field test results from a prototype of a compact Water Vapor DIAL (DIfferential Absorption Lidar) system based on a ceilometer-type design. Vertical profiles of specific humidity were compared with radiosonde data and a Raman lidar instrument. The results indicate that a humidity measurement uncertainty of +/- 5 % is achievable with this type of design up to 3 km or to the top of the boundary layer, whichever is lower. The prototype was operated continuously, including during periods of precipitation, and gives promise for a rugged and low cost instrument suitable for operational use. The new technology is expected to bring significant improvements in short term weather forecasts in the future; potential benefits of this type of data for numerical weather prediction will be discussed.