15 years of research and operations with a Raman lidar for meteorological and climatological applications

Raman lidars are widely used in research to measure the atmospheric profile of temperature and humidity. In operational meteorology, however, the technology is still emerging mostly because of its high costs, the high complexity and the difficulty of calibrating the measurements. The Raman Lidar for Meteorological Observations (RALMO) located at the Federal Office of Meteorology and Climatology MeteoSwiss in Payerne, Switzerland, measures humidity and temperature profiles continuously since 2008 demonstrating the technique’s potential for operational use. We have developed and implemented a calibration method based on the lidar’s solar background measurements allowing for daily calibrations  and independently from external references like radiosondes. We assessed the impact of RALMO observations in the MeteoSwiss operational, convective-scale ensemble data assimilation and forecasting system in two two-week summer and winter experiments revealing the potential to improve the analysis, especially in regions without other profile observations. We further compiled a climatology of tropospheric temperature, water vapor mixing ratio and relative humidity from the 15-year data set and will present first results of relative humidity trends in the troposphere above Payerne, Switzerland.