An LES-based airborne Doppler lidar simulator for investigation of wind profiling in inhomogeneous flow conditions

Abstract. Wind profilingby Doppler lidar is common practice and highly useful in a wide range of applications. Airborne observations can provide additional insights to ground-based systems by allowing for spatially resolved and targeted measurements. This study prepares the ground for an upcoming airborne Doppler lidar system by investigating the measurement process theoretically. To evaluate the future system characteristics and measurement accuracy, a first LES-based airborne Doppler lidar simulator (ADLS) has been developed. The accuracy of retrieved wind profilesunder inhomogeneous flow conditions in the boundary layer is investigated. In general, when using reasonable systemsetups, wind profilingis possible with acceptable error margins. Results allow for determination of preferential system setups and wind profilingstrategies. Under the conditions considered, flow inhomogeneities exert the dominant influence on wind profilingerror. In comparison, both the errors caused by random radial velocity fluctuations due to laser system noise and beam pointing inaccuracy due to system vibrations are of smaller magnitude. Airborne Doppler lidar wind profilingat low wind speeds ( −1 ) requires adequate system setups, retrieval strategies and quality filtering as the retrieved wind speeds can be biased otherwise. The utility of quality filtering criteria for wind profilereliability ( coefficientof determinationand condition number) is examined. While the filtering by the condition numberis useful for all circumstances, an inadequate coefficientof determinationthreshold can bias the retrieved wind speeds. Even with strict quality filtering criteria applied, considerable wind profileretrieval error can exist, especially for steep scan elevation angles of more than 70° from the horizontal or short horizontal averaging distances.