About the effects of polarising optics on lidar signals and the
 Δ90 calibration

Freudenthaler, Volker

doi:10.5194/amt-9-4181-2016

Cited by 158 publications

(250 citation statements)

References 78 publications

(79 reference statements)

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“…Uncertainties in the basic lidar-derived optical properties and the POLIPHON retrieval products are extensively analyzed and discussed by Freudenthaler et al (2009, , Mamouri and Ansmann (2014, 2016), and Bravo-Aranda et al (2016 and will not be discussed here. Typical uncertainties in the basic particle optical properties are given in Table 4 for 532 nm.…”

Section: Retrieval Uncertaintiesmentioning

confidence: 99%

Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

2017

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Abstract. We applied the recently introduced polarization lidar-photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol LongRange Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products.

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Section: Retrieval Uncertaintiesmentioning

confidence: 99%

Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

2017

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“…A proper calibration of particle depolarisation measurements requires accurate measurements of the cross-polarised and co-polarised components of the particle backscattering coefficient. However, accurate measurements of these quantities may be difficult to obtain, often as a result of the depolarising properties of different optical devices included in the receiver (Freudenthaler, 2016). This translates into a non-negligible uncertainty affecting particle depolarisation measurements, which includes both a systematic component (bias) and a random component (statistical error).…”

Section: Basil and The Hope Field Campaignmentioning

confidence: 99%

“…BASIL performs high-resolution and accurate measurements of the vertical profiles of atmospheric temperature and water vapour, both in the daytime and at nighttime, exploiting both the rotational and vibrational Raman lidar techniques in the UV (Di Girolamo et al, 2004, 2009a, 2016Bhawar et al, 2011). Aside from temperature and water vapour, BASIL also measures the vertical profiles of particle backscatter at 354.7, 532 and 1064 nm, as well as particle extinction and depolarisation at 354.7 and 532 nm (Griaznov et al, 2007;Di Girolamo et al, 2009b, 2012a.…”

Section: Basil and The Hope Field Campaignmentioning

confidence: 99%

Clear-air lidar dark band

et al. 2018

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Abstract. This paper illustrates measurements carried out by the Raman lidar BASIL in the frame of the HD(CP) 2 Observational Prototype Experiment (HOPE), revealing the presence of a clear-air dark band phenomenon (i.e. a minimum in lidar backscatter echoes) in the upper portion of the convective boundary layer. The phenomenon is clearly distinguishable in the lidar backscatter echoes at 532 and 1064 nm, as well as in the particle depolarisation data. This phenomenon is attributed to the presence of lignite aerosol particles advected from the surrounding open pit mines in the vicinity of the measuring site. The paper provides evidence of the phenomenon and illustrates possible interpretations for its occurrence.

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“…• with respect to both polarization analyzers (Spinhirne et al, 1982;McGill et al, 2002;Alvarez et al, 2006;David et al, 2012;Wang et al, 2009;Freudenthaler et al, 2009;Neely III et al, 2013;Bravo-Aranda et al, 2013;Freudenthaler, 2016). This type of calibration is not sensitive to polarization effects in the transmitter optics or to any optics upstream of the halfwaveplate.…”

Section: Literature Review Of Depolarization Calibrationsmentioning

confidence: 99%

“…In an alternate version of the half-waveplate calibration, this waveplate may be placed in the transmitter to control the orientation of the plane of polarization of the laser light transmitted to the sky (Liu and Wang, 2013;Neely III et al, 2013;Freudenthaler, 2016;Bu et al, 2017). Eloranta and Piironen (1994) use a Pockels cell in their laser to the same effect.…”

Section: Literature Review Of Depolarization Calibrationsmentioning

confidence: 99%

Depolarization calibration and measurements using the CANDAC Rayleigh–Mie–Raman lidar at Eureka, Canada

et al. 2017

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Abstract. The Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman lidar (CRL) at Eureka, Nunavut, has measured tropospheric clouds, aerosols, and water vapour since 2007. In remote and meteorologically significant locations, such as the Canadian High Arctic, the ability to add new measurement capability to an existing well-tested facility is extremely valuable. In 2010, linear depolarization 532 nm measurement hardware was installed in the lidar's receiver. To minimize disruption in the existing lidar channels and to preserve their existing characterization so far as is possible, the depolarization hardware was placed near the end of the receiver cascade. The upstream optics already in place were not optimized for preserving the polarization of received light. Calibrations and Mueller matrix calculations are used to determine and mitigate the contribution of these upstream optics on the depolarization measurements. The results show that with appropriate calibration, indications of cloud particle phase (ice vs. water) through the use of the depolarization parameter are now possible to a precision of ±0.05 absolute uncertainty (≤ 10 % relative uncertainty) within clouds at time and altitude resolutions of 5 min and 37.5 m respectively, with higher precision and higher resolution possible in select cases. The uncertainty is somewhat larger outside of clouds at the same altitude, typically with absolute uncertainty ≤ 0.1. Monitoring changes in Arctic cloud composition, including particle phase, is essential for an improved understanding of the changing climate locally and globally.

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About the effects of polarising optics on lidar signals and the Δ90 calibration

Cited by 158 publications

References 78 publications

Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

Clear-air lidar dark band

Depolarization calibration and measurements using the CANDAC Rayleigh–Mie–Raman lidar at Eureka, Canada

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