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In this work we probe the INP activity of coastal seawater from near Aarhus in Denmark. 

Aerosol particles with rare specific properties act as nuclei for ice formation. The presence of ice nucleating particles in the atmosphere leads to heterogeneous freezing at warm temperatures and thus these particles play an important role in modulating microphysical properties of clouds. This work presents an ice nucleation cold stage instrument for measuring the concentration of ice nucleating particles in liquids. The cost is ∼ $10 k including an external chiller. Using a lower cost heat sink reduces the cost to ∼ $6 k. The instrument is suitable for studying ambient ice nucleating particle concentrations and laboratory-based process-level studies of ice nucleation. The design plans allow individuals to self-manufacture the cold-stage using 3D printing, off-the-shelf parts, and a handful of standard tools. Software to operate the instrument and analyze the data is also provided. The design is intended to be simple enough that a graduate student can build it as part of a course or thesis project. Costs are kept to a minimum to facilitate use in classroom demonstrations and laboratory classes. 

Secondary organic aerosols contribute a large fraction to atmospheric aerosols. The phase states of secondary organic aerosols influence heterogeneous and multiphase chemistry in the atmosphere and thus climate. In previous studies we have used the dual tandem differential mobility analyzer technique to characterize the temperature- and humidity-dependent viscosity and glass transition temperature of suspended particles. However, the technique requires high particle number concentrations, is a complex setup, is expensive, and measurements are time consuming. Here we demonstrate a new simplified and more cost-effective method to obtain similar data. The technique was used to measure the temperature where the viscosity is ∼107 Pa s for submicron particles composed of binary and ternary mixtures of the sucrose/tartaric acid/citric acid system. Sucrose, tartaric acid and citric acid are taken as proxies for viscous organic aerosol components in the atmosphere. A subset of data were compared to measurements with the dual-tandem differential mobility analyzer method. Results show good agreement between the two techniques. The same mixed chemical systems were modeled using an updated version of the parametric phase diagram model described in Kasparoglu et al. (2021, https://doi.org/10.5194/acp-21-1127-2021) as well as the predictions with the viscosity module of the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients model (AIOMFAC-VISC). Results show that appropriately parameterized mixing rules are suitable to describe these mixtures. We anticipate that the new technique will accelerate discovery of aerosol phase transitions in aerosol research. 

Abstract A multi-agency succession of field campaigns was conducted in southeastern Texas during July 2021 through October 2022 to study the complex interactions of aerosols, clouds and air pollution in the coastal urban environment. As part of the Tracking Aerosol Convection interactions Experiment (TRACER), the TRACER- Air Quality (TAQ) campaign the Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) and the Convective Cloud Urban Boundary Layer Experiment (CUBE), a combination of ground-based supersites and mobile laboratories, shipborne measurements and aircraft-based instrumentation were deployed. These diverse platforms collected high-resolution data to characterize the aerosol microphysics and chemistry, cloud and precipitation micro- and macro-physical properties, environmental thermodynamics and air quality-relevant constituents that are being used in follow-on analysis and modeling activities. We present the overall deployment setups, a summary of the campaign conditions and a sampling of early research results related to: (a) aerosol precursors in the urban environment, (b) influences of local meteorology on air pollution, (c) detailed observations of the sea breeze circulation, (d) retrieved supersaturation in convective updrafts, (e) characterizing the convective updraft lifecycle, (f) variability in lightning characteristics of convective storms and (g) urban influences on surface energy fluxes. The work concludes with discussion of future research activities highlighted by the TRACER model-intercomparison project to explore the representation of aerosol-convective interactions in high-resolution simulations.