Depolarization measurements using the CANDAC Rayleigh-Mie-Raman Lidar at Eureka, Canada

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 reduce its impact on the existing, well-characterized lidar channels, 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 were 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) are now possible to precision within ± 20 % uncertainty at time and altitude resolutions of 5 min × 37.5 m, with higher precision and higher resolution possible in select cases. Monitoring changes in Arctic cloud composition, including particle phase, is essential for a complete understanding of the changing climate locally and globally.

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

Atmospheric Measurement Techniques ◽

10.5194/amt-10-4253-2017 ◽

2017 ◽

Vol 10 (11) ◽

pp. 4253-4277 ◽

Cited By ~ 5

Author(s):

Emily M. McCullough ◽

Robert J. Sica ◽

James R. Drummond ◽

Graeme Nott ◽

Christopher Perro ◽

...

Keyword(s):

Water Vapour ◽

High Arctic ◽

Mueller Matrix ◽

Particle Phase ◽

Relative Uncertainty ◽

Raman Lidar ◽

Canadian High Arctic ◽

Cloud Particle ◽

Measurement Capability ◽

Atmospheric Change

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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Lidar measurements of thin laminations within Arctic clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-4595-2019 ◽

2019 ◽

Vol 19 (7) ◽

pp. 4595-4614

Author(s):

Emily M. McCullough ◽

James R. Drummond ◽

Thomas J. Duck

Keyword(s):

Temperature Inversion ◽

High Arctic ◽

Raman Lidar ◽

Canadian High Arctic ◽

Arctic Clouds ◽

Polar Environment ◽

Stable Temperature ◽

Lidar Measurements ◽

532 Nm ◽

Humidity Profiles

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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Supplementary material to "Intercomparison of atmospheric water vapour measurements in the Canadian high Arctic"

10.5194/amt-2016-330-supplement ◽

2016 ◽

Author(s):

Dan Weaver ◽

Kimberly Strong ◽

Matthias Schneider ◽

Penny M. Rowe ◽

Chris Sioris ◽

...

Keyword(s):

Water Vapour ◽

High Arctic ◽

Atmospheric Water ◽

Canadian High Arctic ◽

Atmospheric Water Vapour ◽

Supplementary Material

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Review of "Intercomparison of atmospheric water vapour measurements in the Canadian high Arctic" by Weaver et al.

10.5194/amt-2016-330-rc1 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

Water Vapour ◽

High Arctic ◽

Atmospheric Water ◽

Canadian High Arctic ◽

Atmospheric Water Vapour

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Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site

Atmospheric Measurement Techniques ◽

10.5194/amt-10-2851-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 2851-2880 ◽

Cited By ~ 5

Author(s):

Dan Weaver ◽

Kimberly Strong ◽

Matthias Schneider ◽

Penny M. Rowe ◽

Chris Sioris ◽

...

Keyword(s):

Water Vapour ◽

Global Climate ◽

Microwave Radiometer ◽

Correlation Coefficients ◽

High Arctic ◽

Atmospheric Water ◽

Canadian High Arctic ◽

Solar Absorption ◽

Atmospheric Water Vapour ◽

Ftir Spectrometer

Abstract. Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian High Arctic research site (Eureka, Nunavut). Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform infrared (FTIR) spectrometers. Close agreement is observed between all combination of datasets, with mean differences ≤  1.0 kg m−2 and correlation coefficients ≥  0.98. The one exception in the observed high correlation is the comparison between the microwave radiometer and a radiosonde product, which had a correlation coefficient of 0.92.A variety of biases affecting Eureka instruments are revealed and discussed. A subset of Eureka radiosonde measurements was processed by the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) for this study. Comparisons reveal a small dry bias in the standard radiosonde measurement water vapour total columns of approximately 4 %. A recently produced solar absorption FTIR spectrometer dataset resulting from the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique is shown to offer accurate measurements of water vapour total columns (e.g. average agreement within −5.2 % of GRUAN and −6.5 % of a co-located emission FTIR spectrometer). However, comparisons show a small wet bias of approximately 6 % at the high-latitude Eureka site. In addition, a new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is shown to provide accurate water vapour measurements (e.g. average agreement was within 4 % of GRUAN), which usefully enables measurements to be taken during day and night (especially valuable during polar night).

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Review of atmospheric water vapour measurements in the Canadian high Arctic

10.5194/amt-2016-330-rc2 ◽

2017 ◽

Author(s):

Anonymous

Keyword(s):

Water Vapour ◽

High Arctic ◽

Atmospheric Water ◽

Canadian High Arctic ◽

Atmospheric Water Vapour

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Intercomparison of atmospheric water vapour measurements in the Canadian high Arctic

10.5194/amt-2016-330 ◽

2016 ◽

Author(s):

Dan Weaver ◽

Kimberly Strong ◽

Matthias Schneider ◽

Penny M. Rowe ◽

Chris Sioris ◽

...

Keyword(s):

Water Vapour ◽

Microwave Radiometer ◽

Correlation Coefficients ◽

High Arctic ◽

Atmospheric Water ◽

Canadian High Arctic ◽

Solar Absorption ◽

Atmospheric Water Vapour ◽

Retrieval Technique ◽

Good Agreement

Abstract. Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian high Arctic research site. Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform spectrometers (FTSs). Good agreement is observed between all combination of datasets, with correlation coefficients ≥ 0.90 showing high correlations. A variety of biases and calibration issues are revealed and discussed for all instruments. A new FTS dataset, resulting from the MUSICA (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique, is shown to offer accurate measurements of water vapour total columns; however, measurements show a small wet bias of approximately 6 %. A new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is also shown to provide accurate water vapour measurements, which usefully enables measurements to be taken during day and night (especially valuable during Polar Night). In addition, limited profile comparisons are conducted using radiosonde and ground-based FTS measurements. Results show MUSICA FTS profiles were within 15 % of radiosonde measurements throughout the troposphere.

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