2025FICUS10271

FICUS: Acquiring Vertical Profiles

1 October 2024 - 30 September 2025

Lead Scientist: Daniel Knopf

Observatory: AMF

Aerosol particles that act as ice-nucleating particles (INPs), thereby initiating ice crystal formation, impact the hydrological cycle and the climate effect of clouds. However, predictive understanding of atmospheric ice formation by primary ice nucleation processes is still insufficient. While ice crystals form aloft in mixed-phase and cirrus clouds, most information about the physicochemical properties of INPs and corresponding freezing parameterizations are based on ground measurements.

The overarching objective of this campaign is to determine the uncertainty in ice formation in cloud and climate models that originates from informing these models by ground-based aerosol particle and INP measurements.

To address this objective, we conduct aerosol-ice formation closure experiments using particle samples collected at the ARM Southern Great Plains (SGP) and Bankhead National Forest (BNF) sites from varying altitudes to assess our predictive understanding of ice formation.

We use the tethered balloon system (TBS) at the ARM SGP and BNF sites equipped with the Size- and Time-Resolved Aerosol Collector (STAC) and the Time-Resolved Bulk Aerosol Collector (TBAC) to collect aerosol particles at different altitudes for offline analyses. Environmental Molecular Sciences Laboratory (EMSL) micro-spectroscopic analytical techniques, complemented by optical microscope-based laboratory ice nucleation experiments, are employed to physicochemically characterize the particle population, identify and characterize individual INPs, and determine corresponding freezing rates. Climate-model-derived, vertically resolved aerosol fields for SGP and BNF locations are applied to predict INP types and INP number concentrations to be compared to the ARM field campaign measurements and closure exercises.