Publication Date:
2016-02-08
Description:
Lidar depolarization measurements distinguish between spherical and non-spherical aerosol particles based on the change of the polarization state between the emitted and received signal. The particle shape information in combination with other aerosol optical properties allow the characterization of different aerosol types and the retrieval of aerosol particle microphysical properties. Regarding the microphysical inversions, lidar depolarization technique is becoming a key method since particle shape information can be used by algorithms based on spheres and spheroids, optimizing the retrieval procedure. Thus, the identification of the depolarization error sources and the quantification of their effects are crucial. This work presents a new tool to assess the lidar polarizing sensitivity and to estimate the systematic error of the volume linear depolarization ratio (δ), combining the Stokes–Müller formalism and the Monte Carlo technique. This tool is applied to a synthetic lidar system and to several EARLINET lidars with depolarization capabilities at 355 or 532 nm. The results evidence that the lidar polarization sensitivity can lead to δ relative errors larger than 100 %, being more probable its overestimation. The lidar systems show δ relative errors larger than 100 % for δ values around the molecular one (~0.004), decreasing up to ~10 % for δ = 0.45. However, among them, POLIS system shows the best behaviour with δ relative errors of 25 % and 0.22 % for δ = 0.004 and δ = 0.45, respectively, evidencing how a proper characterization of the lidar polarizing sensitivity can drastically reduce the δ systematic errors. In this regard, we provide some indications to reduce the lidar polarizing sensitivity and to improve its characterization.
Electronic ISSN:
1867-8610
Topics:
Geosciences
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