Experimental techniques for the calibration of lidar depolarization channels in EARLINET

Belegante, Livio; Bravo-Aranda, Juan Antonio; Freudenthaler, Volker; Nicolae, Doina; Nemuc, Anca; Ene, Dragoş; Alados-Arboledas, L.; Amodeo, Aldo; Pappalardo, Gelsomina; D’Amico, Giuseppe; Amato, Francesco; Engelmann, Ronny; Baars, Holger; Wandinger, Ulla; Papayannis, Alexandros; Kokkalis, P.; Pereira, S.

doi:10.5194/amt-11-1119-2018

Cited by 41 publications

(37 citation statements)

References 47 publications

(78 reference statements)

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“…Analysis of the glare width shows the correspondence to the Gaussian distribution of crystal inclination with the half-width of about 0.4 • (Breon and Dubrulle, 2004;Lavigne et al, 2008). The presence of horizontally oriented crystals is also detected when observing specular spots from the spotlight on the clouds (Borovoi et al, 2008); flutter width is also estimated to be 0.4 • . Lidar observations of the ice clouds provide the basic information about particle orientation Chen et al, 2002;Noel and Sassen, 2005).…”

Section: Introductionmentioning

confidence: 95%

“…Measurements of the polarization of backscattered radiation require careful consideration of polarization distortions in the receiving paths and sensitivity of photodetectors in the channels of original and cross polarization (Freudenthaler, 2016;Belegante et al, 2018;McCullough et al, 2018). The task of observations in lidar networks is to monitor the optical and microphysical properties of aerosol, which requires restoring not only the backscattering coefficient but also the lidar ratio and attenuation.…”

Section: Calibration Of the Polarization Channelsmentioning

confidence: 99%

“…It appears when the lidar is tilted at a significant angle. Depolarization of backscattered radiation has a maximum at a lidar tilt of 30 • for oriented plates and about 60 • for columns (Borovoi et al, 2000). More detailed simulations show that when angular reflection is taken into account, the element a 44 of the light backscattering phase matrix (BSPM) is most informative in determining the flutter (Konoshonkin, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

et al. 2020

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The article describes a scanning polarization lidar, LOSA-M3, developed at the V. E. Zuev Institute of Atmospheric Optics, the Siberian Branch of the Russian Academy of Sciences (IAO SB RAS), as part of the common use center "Atmosphere". The first results of studying the crystalline particle orientation by means of this lidar are presented herein. The main features of the LOSA-M3 lidar are the following: (1) an automatic scanning device, which allows changing the sensing direction in the upper hemisphere at the speed up to 1.5 • s −1 with the accuracy of the angle measurement setting of at least 1 arcmin, (2) separation of the polarization components of the received radiation that is carried out directly behind the receiving telescope without installing the elements distorting polarization, such as dichroic mirrors and beam splitters, and (3) continuous alternation of the initial polarization state (linear-circular) from pulse to pulse that makes it possible to evaluate some elements of the scattering matrix.For testing lidar performance several series of measurements of the ice cloud structure in the zenith scan mode were carried out in Tomsk in April-June 2018. The results show that the degree of horizontal orientation of particles can vary significantly in different parts of the cloud. The dependence of signal intensity on the tilt angle reflects the distribution of particle deflection relative to the horizontal plane and is well described by the exponential dependence. The values of the cross-polarized component in most cases show a weak decline of intensity with the angle. However, these variations are smaller than the measurement errors. We can conclude that they are practically independent of the tilt angle. In most cases the scattering intensity at the wavelength of 532 nm has a wider distribution than at 1064 nm.

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Section: Introductionmentioning

confidence: 95%

Section: Calibration Of the Polarization Channelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

et al. 2020

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“…Unlike in some detailed calibration methods [47][48][49], the most general expression (as shown by Equation (2) [50]) was used to calibrate the volume linear depolarization ratio from MPL lidar data. K is a calibration constant that relates to the differences in the receiver channel gains.…”

Section: Evaluation Of Lidar Datamentioning

confidence: 99%

Lidar Measurements of Dust Aerosols during Three Field Campaigns in 2010, 2011 and 2012 over Northwestern China

Zhou

Xie

et al. 2018

Atmosphere

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Ground-based measurements were carried out during field campaigns in April-June of 2010, 2011 and 2012 over northwestern China at Minqin, the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and Dunhuang. In this study, three dust cases were examined, and the statistical results of dust occurrence, along with physical and optical properties, were analyzed. The results show that both lofted dust layers and near-surface dust layers were characterized by extinction coefficients of 0.25-1.05 km −1 and high particle depolarization ratios (PDRs) of 0.25-0.40 at 527 nm wavelength. During the three campaigns, the frequencies of dust occurrence retrieved from the lidar observations were all higher than 88%, and the highest frequency was in April. The vertical distributions revealed that the maximum height of dust layers typically reached 7.8-9 km or higher. The high intensity of dust layers mostly occurred within the planetary boundary layer (PBL). The monthly averaged PDRs decreased from April to June, which implies a dust load reduction. A comparison of the relationship between the aerosol optical depth at 500 nm (AOD 500 ) and the Angstrom exponent at 440-870 nm (AE 440-870 ) confirms that there is a more complex mixture of dust aerosols with other types of aerosols when the effects of human activities become significant.Atmosphere 2018, 9, 173 2 of 20 due to their complexity and variability. Given this, more advanced instrumentation and greater numbers of measurements are needed in order to decrease the uncertainties of these estimations. We know that radiative forcing by dust aerosols is very sensitive to their vertical structure [22][23][24]. With the help of dust-sensitive instrumentation such as lidar, greater insight into the vertical structure of dust aerosols can be obtained. Polarization-function lidar instruments are highly sensitive to the particle shape, produce a signal that increases with the degree of particle nonsphericity and easily detect the faintest traces of dust [25]. Therefore, dust aerosol profiling using sophisticated and continuous observations by ground-based lidar instruments are required in order to better understand dust storm motions, the temporal-spatial distribution and their effects on the radiation budget, as well as cloud and precipitation development [26].Until now, to the best of our knowledge, only a few campaigns have been performed in order to characterize dust aerosols using ground-based lidar measurements over northwestern China. In the summer of 2002, dust particles exhibiting a high depolarization ratio in the free troposphere were measured using lidar equipment at Dunhuang [27,28]. In Aksu (northwestern Taklimakan Desert), a large amount of dust particles was uplifted: the removal process was observed during the whole dust event via polarization-sensitive lidar [29,30], and the dust layer structure was validated via Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) [31] and ground-based lidar [32]. The temporal-spatial distribution of the ...

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“…In spite of the wide use of polarization lidar technology for detecting depolarized particles, many difficulties in measuring the accurate value of the depolarization ratio still remain (Behrendt & Nakamura, 2002;Belegante et al, 2018). The uncertainty in depolarization measurements from lidars comes from various sources but is mostly related to the difference between the optical and the electronic gain of the lidar's channels, the polarization purity of the laser pulse, and the alignment error between the laser's polarization plane and the polarizer (Behrendt et al, 2002;Bravo-Aranda et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Calibration and Calculation of Polarization Lidar

Xian

Sun

Xu³

et al. 2019

Earth and Space Science

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Although polarization lidar technology has been widely used to detect depolarized particles, many difficulties still exist in measuring accurate values for the depolarization ratio. This ratio is basically related to the difference between the optical and the electronic gain of the lidar's channels, the polarization purity of the laser pulse, and the error in the alignment between the laser's polarization plane and the polarizer. We propose here an algorithm for the calibration and calculation of polarization lidars. Numerical simulations showed that the depolarization ratio profile retrieved from the proposed algorithm agrees well with the simulated profile. The proposed algorithm no longer requires the laser source to be linearly polarized. Instead, the light polarization can be elliptical or random. During the installation process, the polarization of the detector is no longer required to be parallel or perpendicular to the polarization direction of the laser source and can be done in any direction.

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Experimental techniques for the calibration of lidar depolarization channels in EARLINET

Cited by 41 publications

References 47 publications

Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

Lidar Measurements of Dust Aerosols during Three Field Campaigns in 2010, 2011 and 2012 over Northwestern China

Calibration and Calculation of Polarization Lidar

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