Lidar depolarization characterization using a reference system
Abstract. In this study, we will present a new approach for the determination of depolarization parameters of the Nicosia CIMEL CE376 lidar system, using the PollyXT in Limassol as a reference instrument. The method is applied retrospectively to the valuable measurements obtained during the 2021 Cyprus Fall campaign. Lidar depolarization measurements represent valuable information for aerosol typing and for the quantification of some specific aerosol types such as dust and volcanic ash. An accurate characterization is required for quality measurements and to remove instrumental artefacts. This article uses the PollyXT reference calibrated depolarization lidar to evaluate our system's gain ratio and channel cross-talk. This approach uses observations of transported dust from desert regions, with layers in the free troposphere. Above the boundary layer and the highest terrain elevation of the region, we can expect that for long transport aerosols local effects should not affect the aerosol mixture so that we can expect similar depolarization properties at the two stations (separated by ∼60 km). Algebraic equations are used to derive depolarization parameters from the comparison of the volume depolarization ratio measured by the two systems. The applied methodology offers a promising opportunity to evaluate the depolarization parameters of a lidar system, in cases where a priori knowledge of the cross-talk parameters is not available.
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