Measurement Report: Cloud and environmental properties associated with aggregated shallow marine cumulus and cumulus congestus

Abstract

Abstract. Mesoscale organization of marine convective clouds into linear or clustered states is prevalent across the tropical and subtropical oceans and its investigation served as a guiding focus for a series of process study flights, conducted as part of the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) during summer 2020, 2021 and 2022. These select ACTIVATE flights involved a novel strategy for coordinating two aircraft, with respective remote sensing and in situ sampling payloads, to probe regions of organized shallow convection for several hours. The main purpose of this measurement report is to summarize the aircraft sampling approach, describe the characteristics and evolution of the cases, and provide an overview of the datasets that can serve as a starting point for more detailed modeling and analysis studies. Six flights are described, involving a total of 80 dropsonde profiles that capture the environment surrounding clustered shallow convection together with detailed observations of the vertical structure of cloud systems, comprising up to 20 altitude levels that were sampled in situ. Four cases involved deepening convection rooted in the marine boundary layer that developed vertically to 2–5 km with varying precipitation amounts, while two cases captured more complex and developed cumulus congestus systems extending above 5 km. In addition to the thermodynamic and dynamic characterization afforded by dropsonde and in situ measurements, the datasets include cloud and aerosol microphysics, trace gas concentrations, aerosol and droplet composition, and cloud and aerosol remote sensing from high spectral resolution lidar and polarimetry.

Vertical variability of aerosol properties and trace gases over a remote marine region: A case study over Bermuda

“…This suggests that regardless of air mass source, the sampled aerosol had probably undergone 435 some cloud processing to transfer constituents from smaller particles in the Aitken mode and gases to larger particles in the accumulation mode. This is consistent with other ACTIVATE measurements conducted around Bermuda during the time of this study with the Falcon (Crosbie et al, 2024). Expectedly, North American air exhibits systematically higher number concentration with prominent peaks at diameters of 50/143 nm and 45/106 nm for <1 km and 1-3.5 km, respectively.…”