Preprints
https://doi.org/10.5194/amt-2021-268
https://doi.org/10.5194/amt-2021-268

  13 Sep 2021

13 Sep 2021

Review status: this preprint is currently under review for the journal AMT.

The eVe reference polarisation lidar system for Cal/Val of Aeolus L2A product

Peristera Paschou1,2, Nikolaos Siomos1,2, Alexandra Tsekeri1, Alexandros Louridas3, George Georgoussis3, Volker Freudenthaler4, Ioannis Binietoglou1,3, George Tsaknakis3, Alexandros Tavernarakis3, Christos Evangelatos3, Jonas von Bismarck5, Thomas Kanitz6, Charikleia Meleti2, Eleni Marinou1,2, and Vassilis Amiridis1 Peristera Paschou et al.
  • 1IAASARS, National Observatory of Athens, Athens, Greece
  • 2Laboratory of Atmospheric Physics, Physics Department, Aristotle University of Thessaloniki, Thessaloniki, Greece
  • 3Raymetrics S.A., Athens, Greece
  • 4Fakultät für Physik, Meteorologisches Institut, Ludwig-Maximilians-Universität, Munich, Germany
  • 5European Space Agency (ESA-ESRIN), Frascati, Italy
  • 6European Space Agency (ESA-ESTEC), Noordwijk, The Netherlands

Abstract. The eVe dual-laser/dual-telescope lidar system is briefly given here, focusing on the optical and mechanical parts of system’s emission and receiver units. The compact design of linear/circular emission unit along with the linear/circular analyser in the receiver unit, allows eVe to simultaneously reproduce the operation of the ALADIN lidar on board Aeolus as well as the operation of a traditional ground-based polarisation lidar system with linear emission. As such, eVe lidar aims to provide: (a) ground reference measurements for the validation of the Aeolus L2A aerosol products, and (b) the atmospheric conditions for which linear polarisation lidar systems can be considered for Aeolus L2A validation, by identifying any possible biases arisen from the different polarisation state in the emission between ALADIN and these systems, and the detection of only the co-polar component of the returned signal from ALADIN for the L2A products retrieval. In addition, a brief description is given concerning the polarisation calibration techniques that are applied in the system, as well as the developed software for the analysis of the collected signals and the retrieval of the optical products. More specifically, the system’s dual configuration enables the retrieval of the optical properties of particle backscatter and extinction coefficients originating from the two different polarisation states of the emission, the linear and circular depolarisation ratios, as well as the direct calculation of the Aeolus like backscatter coefficient, i.e., the backscatter coefficient that Aeolus would measure from ground. Two cases, one with slightly-depolarising particles and one with moderately-depolarising particles, were selected from the first conducted measurements of eVe in Athens, in order to give a glimpse of the system’s capabilities. In the slightly depolarising scene, the Aeolus like backscatter coefficient agrees well with the actual backscatter coefficient, which is also true when non-depolarising particles are present. The agreement however fades out for strongly depolarising scenes, where an underestimation of ~17 % of the Aeolus like backscatter coefficient is observed when moderately-depolarising particles are probed.

Peristera Paschou et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-268', Anonymous Referee #1, 15 Oct 2021
  • RC2: 'Comment on amt-2021-268', Ronny Engelmann, 01 Nov 2021

Peristera Paschou et al.

Peristera Paschou et al.

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Short summary
eVe lidar measures the optical properties of aerosols and clouds and is designed to provide the European Space Agency’s satellite mission of Aeolus with ground-reference measurements. The system provides linear and circular polarisation measurements, and it has also Raman capabilities. We describe the system design, as well as the polarisation calibration techniques and the developed software for the retrieval of the optical products.