In:
Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 15, No. 7 ( 2022-04-14), p. 2299-2323
Kurzfassung:
Abstract. The eVe dual-laser/dual-telescope lidar system is introduced here, focusing
on the optical and mechanical parts of the system's emission and receiver
units. The compact design of the 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 to operate it as a traditional ground-based polarisation lidar
system with linear emission. As such, the eVe lidar aims to provide (a) ground reference measurements for the validation of the Aeolus L2A aerosol
products and (b) the conditions for which linear polarisation lidar systems
can be considered for Aeolus L2A validation, by identifying any possible
biases arising 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 and 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 the 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 September 2020, in order to
demonstrate 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 ∼18 % of the Aeolus
like backscatter coefficient is observed when moderately depolarising
particles are probed.
Materialart:
Online-Ressource
ISSN:
1867-8548
DOI:
10.5194/amt-15-2299-2022
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2022
ZDB Id:
2505596-3
