Russell J. Perkins

Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled a cold and polluted closed-to-open cell transition with cloud-top temperatures below −20 °C and upstream cloud condensation nuclei concentrations surpassing 600 cm ⁻³ . The aerosol likely originates from Siberian industrial emissions. As the boundary layer deepens prior to and across the transition, driven by strong turbulent surface fluxes and aided by a weakening cloud-top inversion, aerosol number concentrations decrease and supercooled droplet sizes increase, causing ice particles to shift from primarily vapor depositional growth towards riming. Precipitation shafts within open-cells contain abundant large graupel (>5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm h ⁻¹ . Ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Updrafts support liquid water production along convergence boundaries at the upwind cold pool edge. Nonetheless, strong buoyancy fluxes exceeding 200 W m ⁻² prevent sub-cloud decoupling. Ice particle number concentrations increase tenfold across the transition, surpassing 10 L ⁻¹ within open-cells, more than 1000× ice nucleating particle number concentrations. Given that cloud temperatures are too cold for Hallett-Mossop rime splintering, this indicates the importance of other secondary ice production mechanisms. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm^-3, decreasing to 90 cm^-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m^-2 to 270 g m^-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (N_i) are generally 2 L^-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m^-2 collocated with strong updrafts, adjacent to glaciated cloud. N_i surpasses 10 L^-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr^-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m^-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm^-3, decreasing to 90 cm^-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m^-2 to 270 g m^-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (N_i) are generally 2 L^-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m^-2 collocated with strong updrafts, adjacent to glaciated cloud. N_i surpasses 10 L^-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr^-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m^-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

The NASA airborne Arctic Radiation-Cloud-aerosol-Surface-Interaction Experiment (ARCSIX) collected a unique data set providing a near-simultaneous characterization of radiative fluxes, surface, cloud, and aerosol particle properties to address science questions on the surface radiation budget, the processes governing the cloud lifecycle, atmospheric composition, and the interactions between the surface and atmosphere. The overarching goal of ARCSIX was to quantify the contributions of surface, clouds, aerosol particles, and precipitation to summer sea ice melt. ARCSIX consisted of two deployments in 2024 (Spring: 2024-05-28 through 2024-06-13 and Summer: 2024-07-25 through 2024-08-15) to capture pre- and post-melt conditions. ARCSIX provided coordinated remote sensing and in situ sampling using three aircraft in a high-flyer/low-flyer configuration. The NASA G-III served as the high-flying remote sensing platform with two lower flying in situ and near-target remote sensor observing platforms, NASA P-3B and SPEC Inc. Learjet. ARCSIX data are well-suited to improve satellite remote sensing capabilities in the Arctic. ARCSIX included an array of sea ice mass balance buoys deployed in the Lincoln Sea that were regularly overflown during the campaign. ARCSIX research flights spanned the Baffin Bay, Lincoln Sea, west and north of the Canadian Archipelago, and the Greenland north and northeast coasts. During the spring deployment, 19 research flights took place covering 114 flight hours: 10 flights and 68 hours by the P-3B and nine flights and 46 hours by the G-III. During summer, 24 research flights covered 136 flight hours: nine flights and 75 hours by the P-3B, five flights and 26 hours by the G-III, and 10 flights and 35 hours by the Learjet. A total of 13 coordinated flights with 2+ aircraft were carried out. This paper describes the ARCSIX flight strategy, instrumentation, and data set access, and usage details. ARCSIX data are publicly available at https://doi.org/10.5067/SUBORBITAL/ARCSIX/DATA001.

Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm^-3, decreasing to 90 cm^-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m^-2 to 270 g m^-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (N_i) are generally 2 L^-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m^-2 collocated with strong updrafts, adjacent to glaciated cloud. N_i surpasses 10 L^-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr^-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m^-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm-3, decreasing to 90 cm-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m-2 to 270 g m-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (Ni) are generally 2 L-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m-2 collocated with strong updrafts, adjacent to glaciated cloud. Ni surpasses 10 L-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

Bioaerosols have important impacts on human health and potentially on weather and climate through aerosol–cloud interactions. Reciprocally, weather systems can have a large impact on bioaerosols both indirectly through ecosystem-level influences and by playing a more direct role in bioaerosol emission, deposition, and transport. In this work, we discuss the design and initial findings of the Bioaerosols and Convective Storms (BACS) field campaigns, a project targeting the interplay of these two effects. Two BACS field campaigns were conducted in the springs of 2022 and 2023, examining the dynamics of speciated and cloud-relevant aerosol and, especially, bioaerosol observations surrounding precipitation events and cold pool outflows from convective storms. A multifaceted deployment strategy was used, leveraging a combination of online and offline measurements of aerosol and bioaerosol distributions, cloud-relevant properties, and chemical tracers in the context of atmospheric state measurements. The observational strategy included measurements at ground level, a 9-m flux tower, and simultaneous stacked column and profiling multirotor drone measurements and radiosonde launches. Aerosol and bioaerosol responses to precipitation and cold pool events are examined within this manuscript through several case studies highlighting that similar events can produce very different aerosol responses. Reasons for this variability are hypothesized and discussed in the context of our campaign data, and targets for future investigations are suggested. Significance Statement: This work is motivated by understanding a phenomenon with direct human impacts; storm lofting and transport of bioaerosols are known to cause health impacts such as “thunderstorm asthma,” while the same sources of bioaerosols may additionally impact storm evolution. This work describes an extensive campaign dataset, showcasing two cases to highlight how the dataset can be used to probe these questions and raising some of the crucial scientific questions requiring further investigation.

Biological aerosol particles influence atmospheric processes, including cloud ice nucleation through action as ice-nucleating particles (INPs). Their abundance is altered by convective storm processes such as precipitation and cold pools. To improve the understanding of bioaerosol characteristics, sources, and variability during convective storms, we conducted two intensive field campaigns in May–June 2022 and 2023 at a semiarid grassland area in Colorado. The two seasons had contrasting environmental conditions, with exceptionally dry conditions in 2022 and unusually wet conditions in 2023. Bioaerosols were characterized using fluorescence and chemical tracers, while INPs were measured in air (before, during, and after rainfall), precipitation water, and terrestrial source samples; these measurements were aligned with disdrometer- and drone-based observations. Peak fluorescent particle concentrations correlated significantly with cold pool strength (rs=0.81, p

Tropical convective clouds are a critical component of the Earth system. As these As rain falls from these clouds, it evaporates below cloud base and produces convective cold pools. Cold pools are an important component of the atmospheric system, as they influence surface fluxes, impact the spatial distribution of aerosol, including ice nucleating particles (INP), and can initiate new convection. During summer 2025, as part of the Freshwater Fluxes over the Ocean I – Evaporative Fluxes (FreshOcean) deployment, the RAM-CINC (Relating Atlantic Marine Convection, Ice Nuclei and Cold pools) campaign deployed uncrewed aerial systems (UAS; also known as small drones) aboard the R/V Meteor in the tropical eastern Atlantic Ocean. In RAM-CINC, we characterized properties around convective cold pools, including INPs, bioaerosols, and the thermodynamic environment under quiescent and cold-pool-modified conditions. RAM-CINC’s observations are unique and able to elucidate the complex relationship between the near-surface and marine boundary layer in the small convective cold pool features. In this presentation, we will give an overview of our field measurements, including novel above-the-surface in situ measurements of several tropical convective cold pools that vary in strength and lifecycle stage. Because our drone measurements were targeted observations before and after cold pool passage, we will demonstrate the impacts of convective cold pool passage both at ship level and above the surface layer. Initial findings indicate maximum changes in temperature of the cold pools from near zero to -1.2 K. Further, we will show aerosol measurements, including characterization of DNA for bioaerosol particles, aerosol concentrations and size distributions, and INPs, from both the drone flights, the surface of the ship, the ocean surface layer, and rainwater, elucidating the link between the near-surface and broader marine boundary layer.