This study proves that upgraded ground sensors can accurately track atmospheric particles using solar infrared light. The performance of these sensors was evaluated across twelve diverse environments globally, from forests to islands, using trusted reference instruments. Even in cloudy locations, the upgraded sensors performed well. Under clear skies and with proper maintenance, their performance was near-perfect, offering powerful, reliable tools to better understand the atmospheric particles.

Tethered balloon measurements from 149 flights during DOE ARM TRACER over Houston characterize vertical aerosol and CCN structure. Back-trajectory clustering identifies three air mass types – marine, mixed, and urban – with distinct profiles shaped by boundary-layer depth and coastal circulations. A case study shows mesoscale advection simultaneously transforms thermodynamic and aerosol conditions, underscoring the need to constrain meteorology before attributing cloud changes to aerosol forcing.

Cloud condensation nuclei are tiny particles that attract water vapor and help form clouds. A ground-based lidar method can estimate their number at different heights, but assumes the aerosol type does not change with height. Comparisons with aircraft data show good agreement of this method when aerosols are well mixed, but larger errors when stacked layers occur. We also developed an index to flag these complex conditions and indicate when this estimation method is more reliable.

An open-access mass spectral database of identified and unidentified compounds in atmospheric and laboratory-generated organic aerosols is released to aid in future molecular discoveries in the environmental sciences.  Identification of air pollution sources and origins is improved using the ~27,000 mass spectral records in the University of California Berkeley Goldstein Library of Organic Biogenic Environmental Spectra (UCB-GLOBES) database.

Tiny aerosol particles help form cloud droplets and can affect rainfall and climate, but their behavior is hard to predict. We used aircraft measurements over the ocean near the Azores and over the central United States to compare clean and polluted air. We found that particle size and chemical makeup together control how easily clouds form, and organic-rich particles often reduce droplet formation. These results can improve how weather and climate models represent clouds.