Publications

Hong, YL; Di Girolamo, L (2022). An Overview of Aerosol Properties in Clear and Cloudy Sky Based on CALIPSO Observations. EARTH AND SPACE SCIENCE, 9(4), e2022EA002287.

Abstract
A full understanding of the climatological properties of aerosols is an important step towards characterizing their effects on climate. Utilizing the observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, we study cloud-free and cloudy aerosol properties with attention on aerosol and cloud layer relative vertical positions. On a global scale, the cloud-free aerosols account for about 56% of all detected aerosols with a mean optical depth ((tau) over bar (a)) and mean uncertainty of 0.135 +/- 0.047. The cloudy aerosols, accounting for 44%, have a larger (tau) over bar (a) and larger mean uncertainty of 0.143 +/- 0.074 compared to the cloud-free aerosols. The above-cloud aerosols (similar to 4%), primarily composed of elevated smoke, dust/volcanic ash and polluted dust, have a much smaller (tau) over bar (a) of (0.056 +/- 0.038). The below-cloud aerosols (-21%) have (tau) over bar (a) similar to 0.165 +/- 0.087. The below-cloud and cloud-free aerosols show close tau(a) probability density distributions and similar aerosol types, indicating that cloud-free aerosol climatologies from passive sensors are likely representative of all-sky conditions. In addition, about 27% of the detected aerosol profiles are found to have cloud layers vertically connected to the detected aerosol layers. The lidar backscatter profiles of these aerosols have larger median values than the cloud-free, above-cloud and below-cloud aerosols. The seasonal variations of the cloud-free and the cloudy aerosols significantly vary with regions. Our results imply that quantifying the impact of clouds, particularly cirrus due to the wide coverage of cirrus-aerosol overlap, on aerosol direct radiative effect is crucial to assess aerosols' roles in the Earth-climate system.

DOI:
10.1029/2022EA002287

ISSN:
2333-5084