PNNL

Abstract

Accurate estimates of the vertical profile of CCN concentration are crucial to better quantify aerosol–cloud interactions (ACIs). We assessed the correlation between the vertical CCN concentrations obtained from extinction-, satellite-, and model-based retrieval methods and airborne CCN concentrations collected at 0.24% supersaturation (SS) within the 3, 9, 27, and 81 km regions centered over the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) User Facility Southern Great Plains (SGP) site during the spring and summer of 2016. The extinction profiles at a wavelength 355 nm were provided by the ground-based Raman lidar (RL). Our analysis showed moderate correlation between dry-corrected extinction and airborne CCN data. We found the retrieved number concentration of CCN (RNCCN) method showed regression best-fit slopes close to unity and consistent prediction errors for the majority of the data. The Lenhardt et al. (2023) method showed similar conclusions but only during spring, while the Mamouri and Ansmann (2016) method showed poor correlation. The Shinozuka et al. (2015) satellite-based method exhibited reasonable agreement during summer but poor correlation during periods where both high (~1400 cm-3) and low (~50 cm-3) airborne CCN concentrations were observed. The Copernicus Atmosphere Monitoring Service (CAMS) reanalysis modeled 3-D CCN dataset showed a moderate to weak positive correlation but performed poorly at high airborne CCN concentrations. Our findings suggest that the RNCCN method could be promising for routine retrievals and model evaluations of vertical CCN under the diverse meteorological conditions that are typically observed at the SGP site.