Validation of ESA Aeolus wind observations using French ground-based Rayleigh Doppler lidars at midlatitude and tropical sites

French ground-based Rayleigh Doppler lidars deployed at Observatoire de Haute Provence (OHP) in southern France (44° N, 6° E) and Observatoire du Maido (La Reunion island, tropical Indian Ocean, 21° S, 55° E) are among the primary instruments within ESA Aeolus Cal/Val programme.  The ground-based lidars are designed to measure vertical profiles of wind velocity in the altitude range 5 - 70 km with an accuracy better than 1 m/s up to 30 km. The horizontal wind components are obtained by measuring Doppler shift between emitted and backscattered light by means of double-edge Fabry-Perot interferometer. This technique, pioneered by French Service d’Aeronomie in 1989, is implemented in Aeolus ALADIN instrument.

We present the results of validation of Aeolus L2B horizontal line-of-sight wind profiles using the French Doppler lidars and regular radiosoundings. The point-by-point validation exercise relies on the dedicated validation campaigns at OHP in January and Maido in September-October 2019 involving simultaneous lidar acquisitions and collocated radiosonde ascents coincident with the nearest Aeolus overpasses. For evaluation of the long-term variation of the bias in Aeolus wind product, we use twice-daily routine radiosoundings performed by MeteoFrance and regular wind lidar observations at both sites.

The orbital configuration of Aeolus satellite enables 2 overpasses per week above OHP within 100 km range and 2 overpasses in the vicinity of Maido observatory, of which one being within 10 km range. Evaluation of Aeolus wind profiles is done in consideration of the expected mesoscale variability of wind field inferred from numerous lidar-radiosonde intercomparisons at both stations. In addition to the quantitative validation of Aeolus wind profiles, we attempt to evaluate the capacity of Aeolus observations in resolving fluctuations of stratospheric wind field induced by atmospheric gravity waves.