EVE polarization lidar: ESA’s ground reference system for Aeolus L2A products Cal/Val

The EVE (Enhancement and Validation of ESA products) lidar is a mobile, ground-based, polarization lidar system, developed to provide ground reference measurements for the validation of the Aeolus L2A products. The system utilizes a dual-laser/dual-telescope configuration that emits linearly and circularly polarized light at 355 nm  interleaved and detects the linear and circular depolarization on the backscattered signals as well as the Raman backscattering at 387 nm. Consequently, the particle optical properties of backscatter coefficient, extinction coefficient, linear and circular depolarization ratios can be measured by the lidar. Moreover, the system’s dual configuration enables to mimic both the operation of ALADIN on board Aeolus that relies on the circularly polarized emission and the operation of a polarization lidar system with linearly polarized emission. Besides EVE’s main goal of the Aeolus L2A products performance evaluation under a wide variety of aerosol types, EVE can also validate the linear to circular depolarization conversions, which have to be used for the harmonization of the linearly polarized lidar systems with Aeolus, and as such, to evaluate any possible biases of the efforts of these systems on Aeolus L2A validation.