Assessment of lidar depolarization uncertainty by means of a polarimetric lidar simulator
2016
Abstract.
Lidar
depolarizationmeasurements 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 allows the characterization of different aerosol types and the retrieval of aerosol particle
microphysicalproperties. Regarding the
microphysicalinversions, the
lidar
depolarizationtechnique 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
depolarizationerror sources and the quantification of their effects are crucial. This work presents a new tool to assess the
systematic errorof the volume linear
depolarization ratio( δ ), combining the Stokes–Muller formalism and the complete sampling of the error space using the
lidarmodel presented in Freudenthaler (2016a). This tool is applied to a synthetic
lidarsystem and to several EARLINET
lidarswith
depolarizationcapabilities at 355 or 532 nm. The
lidarsystems show relative errors of δ larger than 100 % for δ values around molecular linear
depolarization ratios(∼ 0.004 and up to ∼ 10 % for δ = 0.45). However, one system shows only relative errors of 25 and 0.22 % for δ = 0.004 and δ = 0.45, respectively, and gives an example of how a proper identification and reduction of the main error sources can drastically reduce the
systematic errorsof δ . In this regard, we provide some indications of how to reduce the
systematic errors.
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