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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 Aug 2018

Research article | 07 Aug 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

CALIPSO Lidar Calibration at 532 nm: Version 4 Daytime Algorithm

Brian J. Getzewich1, Mark A. Vaughan2, William H. Hunt1,†, Melody A. Avery2, Kathleen A. Powell2, Jason L. Tackett1, David M. Winker2, Jayanta Kar1, Kam-Pui Lee1, and Travis Toth2,3 Brian J. Getzewich et al.
  • 1Science Systems and Applications Inc., Hampton, Virginia, USA
  • 2NASA Langley Research Center, Hampton, Virginia, USA
  • 3University of North Dakota, Grand Forks, North Dakota, USA
  • deceased

Abstract. The Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission released version 4.00 of their lidar level 1 data set in April of 2014, and subsequently updated this to version 4.10 in November of 2016. The primary difference in the newly released version 4 (V4) data is a suite of updated calibration coefficients calculated using substantially revised calibration algorithms. This paper describes the revisions to the V4 daytime calibration procedure for the 532nm parallel channel. As in earlier releases, the V4 daytime calibration coefficients 15 are derived by scaling the raw daytime signals to the calibrated nighttime signals acquired within a calibration transfer region, and thus the new V4 daytime calibration benefits from improvements made to the V4 532nm nighttime calibration. The V4 calibration transfer region has been moved upward from the upper troposphere to the more stable lower stratosphere. The identification of clear-air columns by an iterative thresholding scheme, crucial to selecting the observation regions used for calibration, now uses uncalibrated 1064nm data rather than recursively using the 20 calibrated 532nm data as was done in version 3 (V3). A detailed account of the rationale and methodology for this new calibration approach is provided, along with results demonstrating the improvement of this calibration over the previous version. Extensive validation data acquired by NASA's airborne high spectral resolution lidar (HSRL) shows that during the daytime the average difference between collocated CALIPSO and HSRL measurements of 532nm attenuated backscatter coefficients is reduced from 3.3%±3.1% in V3 to 1.0%±3.5% in V4.

Brian J. Getzewich et al.
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Status: final response (author comments only)
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Brian J. Getzewich et al.
Brian J. Getzewich et al.
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Special issue
Short summary
We describe the new architecture of the version 4 (V4) CALIOP 532 nm daytime calibration procedures. Critical differences from the versions include moving the night-to-day calibration transfer region into the lower stratosphere coupled to a multi-dimensional data averaging scheme. Comparisons to collocated high spectral resolution lidar (HSRL) measurements shows that the V4 532 nm daytime attenuated backscatter coefficients replicate the HSRL data to within 1.0 % ± 3.5 %.
We describe the new architecture of the version 4 (V4) CALIOP 532 nm daytime calibration...