Three-channel single-wavelength lidar depolarization calibration

McCullough, Emily; Sica, R. J.; Drummond, J. R.; Nott, G. J.; Perro, C. W.; Duck, Thomas J.

doi:10.5194/amt-11-861-2018

Cited by 3 publications

(4 citation statements)

References 13 publications

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“…In this case, the photodetectors change places with respect to the polarization components. Turning by 90 • can be carried out physically by rotating the entire photodetector unit (Yoshida et al, 2010;Strawbridge, 2013) or by rotating the half-wave phase plate, which can be installed both in the transmitter channel (Spinhirne et al, 1982) and the receiver (McGill et al, 2002;Reichardt et al, 2012). In previous lidars of the LOSA series (Balin et al, 2009), mechanical rotation of the photodetector unit by 90 • was used.…”

Section: Calibration Of the Polarization Channelsmentioning

confidence: 99%

“…It should be mentioned that most of the works used the 532 nm wavelength for measurements. Due to technical difficulties, only a small number of works use the first harmonic of the Nd:YAG laser (1064 nm) that is optimal for recording aerosol layers (McGill et al, 2002;Burton et al, 2015;Haarig et al, 2016Haarig et al, , 2017Veselovskii et al, 2017). The assumption of independence of the crystalline particle scattering of the wavelength is not always justified (Tao et al, 2008;Vaughan et al, 2010;.…”

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: Calibration Of the Polarization Channelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…Not all of the laminations are confined to the altitudes covered by the temperature inversion, when present. Radke et al (1989) suggestbased on the work of Andraea et al (1988), McElroy and Smith (1986) and Wakimoto and McElroy (1986) that thin, elevated, hazes can also occur at mid-latitudes and these, too, occur only in regions of great thermal stability. If the atmosphere were not vertically stable, then these laminations could not persist as they would be removed by the vertical mixing.…”

Section: Meteorological Considerationsmentioning

confidence: 99%

Lidar measurements of thin laminations within Arctic clouds

2019

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Abstract. Very thin ( < 10 m) laminations within Arctic clouds have been observed in all seasons using the Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh–Mie–Raman lidar (CRL) at the Polar Environment Atmospheric Research Laboratory (PEARL; located at Eureka, Nunavut, in the Canadian High Arctic). CRL's time (1 min) and altitude (7.5 m) resolutions from 500 m to greater than 12 km altitude make these measurements possible. We have observed a variety of thicknesses for individual laminations, with some at least as thin as the detection limit of the lidar (7.5 m). The clouds which contain the laminated features are typically found below 4 km, can last longer than 24 h, and occur most frequently during periods of snow and rain, often during very stable temperature inversion conditions. Results are presented for range-scaled photocounts at 532 and 355 nm, ratios of 532∕355 nm photocounts, and the 532 nm linear depolarization parameter, and with context provided by twice-daily Eureka radiosonde temperature and relative humidity profiles.

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“…3e is the 532 nm linear depolarization parameter. This is calculated using the d 1 method fromMcCullough et al (2018), which is the technically simplest method to calculate the desired quantity. The downside of the method is that one of the measurement channels has very low signal rates, leading to a generally low signal to noise ratio (SNR).…”

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confidence: 99%

Lidar measurements of thin laminations within Arctic clouds

McCullough¹,

Drummond²,

Duck³

2018

Preprint

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Very thin (< 10 m) laminations within Arctic clouds have been observed in all seasons using the Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman lidar (CRL) at the Polar Environment Atmospheric Research Laboratory (PEARL; located at Eureka, Nunavut in the Canadian High Arctic). CRL's high time (1 min) and altitude (7.5 m) resolution from 500 m to 12+ km altitude make these measurements possible. We have observed a variety of thicknesses 5 for individual laminations, with some at least as thin as the detection limit of the lidar (7.5 m). The clouds which contain the laminated features are typically found below 4 km, can last longer than 24 h, and occur most frequently during periods of snow and rain, often during very stable temperature inversion conditions. Results are presented for range-scaled photocounts at 532 nm and at 355 nm, ratios of 532/355 nm photocounts, and 532 nm linear depolarization parameter, with context provided by twice-daily Eureka radiosonde temperature and relative humidity profiles. 10 Figure 1. Thin laminated layers within an Arctic cloud. 532 nm range-scaled counts from the CRL lidar at Eureka, Nunavut showing quasihorizontal layers, as thin as 7.5 m each, within a cloud on 7 March 2016, during snowing conditions.Atmos. Chem. Phys. Discuss., https://doi.High resolution studies of clouds, and in particular Arctic clouds, are essential for a full understanding of the clouds' microphysical properties. Even if the clouds appear identical at low resolution, significantly different processes may occur in morphologically distinct clouds, e.g. a layered cloud in which the size of the layers is smaller than the resolution of the measuring instrument or model, and a smooth cloud with the same average optical properties as the layered cloud. 5 Figure 1 shows 532 nm range-scaled counts (counts × altitude 2 ) from the Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman lidar (CRL) at the Polar Environment Atmospheric Research Laboratory (PEARL; located at Eureka, Nunavut in the Canadian High Arctic). The figure shows quasi-horizontal layers, as thin as 7.5 m each, within a cloud on 7 March 2016, while snowing conditions were reported at the surface. CRL's highest resolution is required to resolve the thinnest laminations. There are descending features in Fig. 1 interpreted to be fall streaks. These do not 10 seem to interfere with the persistence of the laminated features. There are at least 16 layers in the region between 3.25 and 3.75 km at 06:30 UTC, giving a mean layer thickness of 15 m. Some layers merge together into thicker layers, and split again into thinner layers, over the course of this 5.5 h plot. This example is not an isolated case. Similar phenomena are displayed frequently the CRL measurements, with individual cases often spanning several days in a row.Figure 2 shows selected profiles of range-scaled 532 nm photocounts from Fig. 1 as a function of altitude for four consecutive 15 minutes just after 06:40 UTC, each of...

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Three-channel single-wavelength lidar depolarization calibration

Cited by 3 publications

References 13 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 thin laminations within Arctic clouds

Lidar measurements of thin laminations within Arctic clouds

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