25 Oct 2023
 | 25 Oct 2023
Status: this preprint is currently under review for the journal AMT.

An iterative algorithm to simultaneously retrieve aerosol extinction and effective radius profiles using the CALIOP lidar

Liang Chang, Jing Li, Jingjing Ren, Changrui Xiong, and Lu Zhang

Abstract. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite has been widely used in climate and environment studies to obtain the vertical profiles of atmospheric aerosols. To retrieve the vertical profile of aerosol extinction, the CALIOP algorithm assumes column-averaged lidar ratios based on a clustering of aerosol optical properties measured at surface stations. On one hand, these lidar ratio assumptions may not be appropriate or representative at certain locations. One the other hand, the two-wavelength design of CALIOP has the potential to constrain aerosol size information, which has not been considered in the operational algorithm. In this study, we present a modified inversion algorithm to simultaneously retrieve aerosol extinction and effective radius profiles using two-wavelength elastic lidars such as the CALIOP. Specifically, a look-up table is built to relate the lidar ratio with the Ångström exponent calculated using aerosol extinction at the two wavelengths, and the lidar ratio is then determined iteratively without a priori assumption. The retrieved two-wavelength extinction at each layer is then converted to particle effective radius assuming a lognormal distribution. The algorithm is tested on synthetic data, Raman lidar measurements and then finally the real CALIOP backscatter measurements. Results show improvements over the CALIPSO operational algorithm by comparing with ground-based Raman lidar profiles.

Liang Chang et al.

Status: open (until 28 Dec 2023)

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  • RC1: 'Comment on amt-2023-223', Anonymous Referee #1, 13 Nov 2023 reply

Liang Chang et al.

Liang Chang et al.


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Short summary
We described a modified lidar inversion algorithm to retrieve aerosol extinction and size distribution simultaneously from two wavelengths elastic lidar measurements. Its major advantage is that the lidar ratio of each layer is determined iteratively by the lidar ratio-AE look-up table. The algorithm was applied to the Raman lidar and CALIOP measurements. The retrieved results by our method are in good agreement with by Raman method.