PNNL

Abstract

Cloud property measurements are integral to atmospheric research since they will be used for process studies and need to be included in earth system models. During the Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) in 2017/2018, a variety of cloud probes using different measurement techniques (shadow imaging, scattering and holography) and liquid water content probes (hotwires, bulk measurements) were deployed. This study examines the performance of the deployed cloud probes during ACE-ENA and compares the results between them. Due to the wide, overlapping range of deployed cloud probes, it is possible here to compare in-situ cloud data from several different measurement methods for small cloud droplets up to 50 µm, and for a subset of instruments up to 100 µm. Data processing was tailored to the conditions found during the deployment, i.e. warm low clouds, which eliminated the complication of ice phase presence and led to good agreement between all deployed cloud probes. Improvements included noise reduction for the holographic cloud probe and better out-of-focus correction for shadow imaging probes for liquid droplets. Comparison between direct liquid water content measurements and cloud probes showed generally better agreement at higher droplet number concentrations (>120/cm3), possibly due to inefficient sampling at lower number concentrations (