Beyond their task to serve as airborne demonstrators for future spaceborne missions our lidar systems are frequently used in scientific campaigns, both national and international, ranging from tropical to the arctic latitudes, to study atmospheric dynamics, exchange processes as well as cloud and particle properties, through range-resolved measurements of wind, water vapour, trace gases and aerosol. Furthermore, lidar measurement can help to pinpoint deficits in current weather forecast or climate models.
Our lidar systems are also regularly employed for the validation of satellite instruments as well as to gather comprehensive data sets that serve as the input for end-to-end simulations of future lidar-based satellite instruments. Recently, the airborne Doppler wind lidars have been used in case studies such as to resolve dynamic structures in the tropics connected to the African monsoon, to investigate mountain wave phenomena, and to improve weather forecast through targeted observations. We also use this technique to study wake vortices behind aircraft to help improving safety in air transport. In the past years, the water vapour differential absorption lidar (DIAL) has been used in several tropical campaigns mainly to study the air mass transport into the tropical lower stratosphere or the outflow of deep tropical thunderstorms. Recent campaigns in Central Europe and in the Arctic, using the newly developed WALES airborne demonstrator, have been, inter alia, dedicated to test the hypothesis that targeted observation in sensitive regions will improve forecasts rather than non-targeted observations.
Aerosol optical properties of Saharan dust and its mixing process with marine, urban, and biomass burning aerosol have been studied using a newly developed High Spectral Resolution Lidar (HSRL). In co-operation with industrial partners a helicopter-borne methane lidar to detect leaks in natural gas transmission pipelines was developed some years ago.
In order to advance the lidar technology within the meteorological services and climate research community, theoretical and experimental studies are carried out. As an example, the feasibility and benefit of future DIAL systems for greenhouse gas monitoring was analysed and supported by the development of an experimental system to measure carbon dioxide.
All these tasks remain a challenge for the future, particularly with regard to the new research aircraft HALO. A variety of campaigns using our lidars combined with other sensors onboard HALO are right in the planning stage to investigate cirrus cloud formation, the Indian monsoon, tropospheric aerosol or processes in the polar atmosphere.