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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 11
Atmos. Meas. Tech., 11, 6107-6135, 2018
https://doi.org/10.5194/amt-11-6107-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: CALIPSO version 4 algorithms and data products

Atmos. Meas. Tech., 11, 6107-6135, 2018
https://doi.org/10.5194/amt-11-6107-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Nov 2018

Research article | 12 Nov 2018

The CALIPSO version 4 automated aerosol classification and lidar ratio selection algorithm

Man-Hae Kim1, Ali H. Omar2, Jason L. Tackett3, Mark A. Vaughan2, David M. Winker2, Charles R. Trepte2, Yongxiang Hu2, Zhaoyan Liu2, Lamont R. Poole3, Michael C. Pitts2, Jayanta Kar3, and Brian E. Magill3 Man-Hae Kim et al.
  • 1NASA Postdoctoral Program (USRA), Hampton, VA, USA
  • 2NASA Langley Research Center, Hampton, VA, USA
  • 3Science Systems and Applications, Inc., Hampton, VA, USA

Abstract. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) version 4.10 (V4) level 2 aerosol data products, released in November 2016, include substantial improvements to the aerosol subtyping and lidar ratio selection algorithms. These improvements are described along with resulting changes in aerosol optical depth (AOD). The most fundamental change in the V4 level 2 aerosol products is a new algorithm to identify aerosol subtypes in the stratosphere. Four aerosol subtypes are introduced for stratospheric aerosols: polar stratospheric aerosol (PSA), volcanic ash, sulfate/other, and smoke. The tropospheric aerosol subtyping algorithm was also improved by adding the following enhancements: (1) all aerosol subtypes are now allowed over polar regions, whereas the version 3 (V3) algorithm allowed only clean continental and polluted continental aerosols; (2) a new dusty marine aerosol subtype is introduced, representing mixtures of dust and marine aerosols near the ocean surface; and (3) the polluted continental and smoke subtypes have been renamed polluted continental/smoke and elevated smoke, respectively. V4 also revises the lidar ratios for clean marine, dust, clean continental, and elevated smoke subtypes. As a consequence of the V4 updates, the mean 532nm AOD retrieved by CALIOP has increased by 0.044 (0.036) or 52% (40%) for nighttime (daytime). Lidar ratio revisions are the most influential factor for AOD changes from V3 to V4, especially for cloud-free skies. Preliminary validation studies show that the AOD discrepancies between CALIOP and AERONET–MODIS (ocean) are reduced in V4 compared to V3.

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This paper discusses recent advances made in distinguishing among different aerosols species detected in the CALIPSO lidar measurements. A new classification algorithm now classifies four different aerosol types in the stratosphere, and the number of aerosol types recognized in the troposphere has increased from six to seven. The lidar ratios characterizing each type have been updated and the effects of these changes on CALIPSO retrievals of aerosol optical depth are examined in detail.
This paper discusses recent advances made in distinguishing among different aerosols species...
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