Reviewing How to Best Measure and Model Ice-Nucleating Particles

Published: 22 July 2022

DOE Early Career Research Program Award recipient leads new paper

The following is based on a story by Beth Mundy, Pacific Northwest National Laboratory (PNNL).

Illustration showing detailed, real-world view of the world above a pixelated, modeled version of the same image
A new review article led by a team at Pacific Northwest National Laboratory (PNNL) analyzes the literature surrounding how researchers model and measure ice-nucleating particles. Illustration is by Cortland Johnson, PNNL.

By helping ice form in clouds, ice-nucleating particles (INPs) play an important role in weather and climate. Researchers at PNNL have been studying how to best measure and model INPs.

A team led by PNNL atmospheric scientist Susannah Burrows recently authored a review article in Reviews of Geophysics that analyzes the literature surrounding INP modeling and measurements.

In addition to summarizing what scientists currently know about INPs, it identifies research priorities to better understand the fundamental particle sources and processes that control the concentrations and variability of INPs as well as how to model them.

“We’re taking PNNL’s measurements-to-modeling philosophy and applying it to INPs in this article,” says Burrows, whose paper acknowledges support from the U.S. Department of Energy’s (DOE) Atmospheric System Research (ASR) program.

On the User Executive Committee for DOE’s Atmospheric Radiation Measurement (ARM) user facility, Burrows is the science theme representative for aerosol modeling.

“To accurately represent INPs in models,” continues Burrows, “we need to understand where they come from, how they behave in real-world atmospheric conditions, and which processes control their concentrations and behavior.”

The paper also includes authors from the National Center for Atmospheric Research, Brookhaven National Laboratory, Colorado State University, and Tsinghua University.

Modeling INPs

Two people talk on top of a platform at the Southern Great Plains atmospheric observatory in Oklahoma.
The Southern Great Plains is an ideal location for studying how agricultural soil particles affect atmospheric ice-nucleating particle concentrations. Photo is by Susannah Burrows, PNNL.

Currently, there is a disconnect between observations and the atmospheric models that simulate clouds and their role in weather and climate. Many models do not use INP concentrations to predict ice formation in clouds, relying only on environmental information such as temperature and humidity.

Many of the models that use INPs in their freezing predictions base their INP representations on laboratory studies of particle-induced freezing. While these laboratory studies can be powerful, there is still uncertainty as to whether they accurately simulate atmospheric conditions. The research team suggests that combining laboratory work with targeted observations could create a richer perspective.

Importantly, the team created a summary of relative levels of scientific understanding for key INP sources in both observations and modeling. They incorporated information on studies of aerosol particles, which give rise to INPs. They found that desert dust is the most well-understood INP source across modeling and observations. Biological particle fragments, such as leaf debris and pollen fragments, are among the least understood due to measurement-related challenges.

This type of overview provides useful information for the INP community to plan future work. “We hope that this review can highlight areas where additional data could make a major difference,” says Burrows.

Burrows received a DOE Early Career Research Program Award in 2018 to study how particles from agriculture and sea spray influence the earth system through their effects on INPs.

As part of this project, Burrows recently led a field campaign at ARM’s Southern Great Plains atmospheric observatory in Oklahoma to collect data on sources of INPs in an agriculturally dominated area. The measurements included several different instruments to quantify INPs and characterize the physical and chemical properties of particles in real time.

The campaign also collected aerosol and soil samples for additional laboratory-based analysis. Samples collected onboard the ARM tethered balloon system will be used to assess INP concentrations and aerosol characteristics at different altitudes. The combination of field data and laboratory studies will be used to design additional INP representations for models.

You can read the new article on the Reviews of Geophysics website.

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ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.