Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.248 IF 3.248
  • IF 5-year value: 3.650 IF 5-year 3.650
  • CiteScore value: 3.37 CiteScore 3.37
  • SNIP value: 1.253 SNIP 1.253
  • SJR value: 1.869 SJR 1.869
  • IPP value: 3.29 IPP 3.29
  • h5-index value: 47 h5-index 47
  • Scimago H index value: 60 Scimago H index 60
Volume 11, issue 3 | Copyright

Special issue: CALIPSO version 4 algorithms and data products

Atmos. Meas. Tech., 11, 1459-1479, 2018
https://doi.org/10.5194/amt-11-1459-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Mar 2018

Research article | 14 Mar 2018

CALIPSO lidar calibration at 532 nm: version 4 nighttime algorithm

Jayanta Kar1,2, Mark A. Vaughan2, Kam-Pui Lee1,2, Jason L. Tackett1,2, Melody A. Avery2, Anne Garnier1, Brian J. Getzewich1,2, William H. Hunt1,2,†, Damien Josset1,2,a, Zhaoyan Liu2, Patricia L. Lucker1,2, Brian Magill1,2, Ali H. Omar2, Jacques Pelon3, Raymond R. Rogers2,b, Travis D. Toth2,4, Charles R. Trepte2, Jean-Paul Vernier1,2, David M. Winker2, and Stuart A. Young1 Jayanta Kar et al.
  • 1Science Systems and Applications Inc., Hampton, VA, USA
  • 2NASA Langley Research Center, Hampton, VA, USA
  • 3LATMOS, Université de Versailles Saint Quentin, CNRS, Verrières le Buisson, France
  • 4Department of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA
  • anow at: US Naval Research Laboratory, Stennis Space Center, MS, USA
  • bnow at: Lord Fairfax Community College, Middletown, VA, USA
  • deceased

Abstract. Data products from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) were recently updated following the implementation of new (version 4) calibration algorithms for all of the Level 1 attenuated backscatter measurements. In this work we present the motivation for and the implementation of the version 4 nighttime 532nm parallel channel calibration. The nighttime 532nm calibration is the most fundamental calibration of CALIOP data, since all of CALIOP's other radiometric calibration procedures – i.e., the 532nm daytime calibration and the 1064nm calibrations during both nighttime and daytime – depend either directly or indirectly on the 532nm nighttime calibration. The accuracy of the 532nm nighttime calibration has been significantly improved by raising the molecular normalization altitude from 30–34km to the upper possible signal acquisition range of 36–39km to substantially reduce stratospheric aerosol contamination. Due to the greatly reduced molecular number density and consequently reduced signal-to-noise ratio (SNR) at these higher altitudes, the signal is now averaged over a larger number of samples using data from multiple adjacent granules. Additionally, an enhanced strategy for filtering the radiation-induced noise from high-energy particles was adopted. Further, the meteorological model used in the earlier versions has been replaced by the improved Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), model. An aerosol scattering ratio of 1.01 ± 0.01 is now explicitly used for the calibration altitude. These modifications lead to globally revised calibration coefficients which are, on average, 2–3% lower than in previous data releases. Further, the new calibration procedure is shown to eliminate biases at high altitudes that were present in earlier versions and consequently leads to an improved representation of stratospheric aerosols. Validation results using airborne lidar measurements are also presented. Biases relative to collocated measurements acquired by the Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) are reduced from 3.6 % ± 2.2 % in the version 3 data set to 1.6 % ± 2.4 % in the version 4 release.

Publications Copernicus
Special issue
Download
Short summary
We present the motivation for and the implementation of the version 4.1 nighttime 532 nm parallel-channel calibration of the CALIOP lidar. The accuracy of calibration is significantly improved by raising the molecular normalization altitude from 30–34 km to 36–39 km to substantially reduce stratospheric aerosol contamination. The new calibration procedure eliminates biases in earlier versions and leads to an improved representation of stratospheric aerosols.
We present the motivation for and the implementation of the version 4.1 nighttime 532 nm...
Citation
Share