Theoretical Derivation of Aerosol Lidar Ratio using Mie Theory for CALIOP-CALIPSO and OPAC Aerosol Models
The extinction-to-backscattering ratio, popularly known as lidar (light detection and ranging) ratio of atmospheric aerosols is an important optical property, which is essential to retrieve the extinction profiles of atmospheric aerosols. Lidar satellite observations can provide the global coverage...
| Main Authors: | , |
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| Format: | Text |
| Language: | English |
| Published: |
2023
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/amt-2023-104 https://amt.copernicus.org/preprints/amt-2023-104/ |
| Summary: | The extinction-to-backscattering ratio, popularly known as lidar (light detection and ranging) ratio of atmospheric aerosols is an important optical property, which is essential to retrieve the extinction profiles of atmospheric aerosols. Lidar satellite observations can provide the global coverage of atmospheric aerosols along with their vertical extent. NASA’s Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP) on-board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) is the only space-based platform available so far, that provides the vertical profiles of extinction due to atmospheric aerosols. A physics-based theoretical approach is presented in the present paper that estimates lidar ratio values for CALIPSO aerosol models, which can be used as inputs to determine the extinction profiles of aerosols using CALIPSO data. The developed methodology was also qualified by comparing it with the lidar ratio values derived using AERONET datasets. Lidar ratio for CALIPSO aerosols models were estimated in the range of 38.72 sr to 85.98 sr at 532 nm whereas, at 1064 nm lidar ratio varied between 20.11 sr to 71.11 sr depending upon the aerosol type and their size distributions. Aerosols are compositions of various particles and thus the presence of water vapour in the atmosphere can affect the optical properties of the aerosols. Thus, the effect of relative humidity on lidar ratio was studied using Optical Properties of Cloud and Aerosols software tool (OPAC) aerosol models, which are the standard aerosol models against the cluster classified AERONET and CALIPSO aerosol models. Water soluble particles contribute substantially in clean continental, clean marine, tropical marine and desert aerosol models and are hygroscopic in nature. Hygroscopic sulfate particles dominate the Antarctic aerosols during summertime. In presence of relative humidity between 0–80%, the lidar ratio values were observed to decrease from 53.59 sr to 47.13 sr, 53.66 sr to 47.15 sr, 53.70 sr to 47.16 sr and 55.32 ... |
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