Research / Research Highlights

Global Observations of the Particles that Trigger Ice in Clouds

Submitter

Creamean, Jessie — Colorado State University

Area of Research

Cloud-Aerosol-Precipitation Interactions

Journal Reference

Creamean J, C Hume, M Vazquez, and A Theisen. 2025. "Long-term measurements of ice nucleating particles at Atmospheric Radiation Measurement (ARM) sites worldwide." Earth System Science Data, 17(12), 10.5194/essd-17-6943-2025.

Science

This work compiles one of the most extensive global records of ice nucleating particles (INPs), which are atmospheric particles that help form ice in clouds, by systematically measuring their concentrations at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) User Facility's locations and often for multiple years using the same method.

Impact

By making this comprehensive INP dataset publicly available, the study provides critical observational constraints that will help scientists improve earth system and weather models’ representation of cloud formation and precipitation processes, ultimately reducing uncertainties in atmospheric predictions.

Summary

INPs are a key but poorly quantified part of the atmosphere because they trigger the formation of ice crystals in clouds—influencing cloud properties, precipitation, and Earth’s atmospheric feedbacks. This paper presents a large, standardized ARM data set of immersion-mode INP concentrations measured across a variety of environments including agricultural plains, high mountains, Arctic coastlines, marine regions, and urban areas. Samples are collected at fixed stations, during mobile field campaigns, and via tethered balloons, then processed with a consistent analytical pipeline to ensure comparability. The data set includes both total INP concentrations and samples treated to distinguish biological, organic, and inorganic INP types, and features a continuous multi-year record at a central U.S. site alongside multi-site records elsewhere. By documenting seasonal and regional differences in INPs and archiving these measurements within the ARM Data Archive, this work supports a wide range of research from basic observational studies to model development, helping constrain aerosol-cloud interactions across different atmospheric regimes.