Aerosol extinction retrieval for dust from the CALIOP measurements using the MODIS AOD as a constraint
Abstract
The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a space-borne lidar system that can measure vertical distribution of the atmosphere over the globe. The vertical profiles of aerosol extinction coefficient are retrieved from the CALIOP measurements. In the aerosol extinction retrieval, the lidar ratio is very important parameter and one of the most significant source of uncertainty. The CALIOP's aerosol retrieval algorithm defines seven aerosol types and uses pre-determined lidar ratios for those aerosols based on the cluster analysis from the Aerosol Robotic Network (AERONET) measurements.
In this study, aerosol extinction coefficients and lidar ratios are retrieved from the CALIOP Level 1B product using aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS; Dark Target over ocean and Deep Blue over land) as a constraint for dust aerosols from 2007 to 2010. Lidar ratio for dust layer is adjusted from its initial value during the retrieval until the CALIOP AOD matches with collocated MODIS AOD. The retrieval is performed from 30 km to the surface with fixed lidar ratio of 30 sr for clear air. The mean (± standard deviation) retrieved lidar ratios for dust aerosol are 39.7 ± 24.1 sr over ocean and 49.9 ± 44.1 sr over land. There is relatively large difference in dust lidar ratio between land and ocean in this study, whereas currently used lidar ratio for dust in the CALIOP algorithm is a fixed value of 44 sr for both land and ocean. The retrieved lidar ratios are strongly related with AOD difference between CALIOP and MODIS. It also has distinct regional variation. Detailed discussion will be shown in the presentation.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A13J2938K
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0319 Cloud optics;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0321 Cloud/radiation interaction;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0360 Radiation: transmission and scattering;
- ATMOSPHERIC COMPOSITION AND STRUCTURE