Plants are reservoirs of bacteria and fungal spores, and the soils they grow in are full of these and other particles composed of clay minerals and decaying plant matter. When disturbed by natural or human-caused events such as fires, windstorms, and agricultural activities, these microscopic particles are released into the air, eventually attracting moisture to form clouds. In atmospheric science parlance, the special few of these particles that trigger the formation of ice crystals are classified as “ice nucleating particles.”

Why is this important? Depending on the source of the particle—natural or human-caused—different types of ice crystals are formed. The variety and number of ice crystals can affect the transfer of solar and thermal energy in clouds, and how efficiently the cloud produces precipitation, if at all. However, scientists remain largely in the dark as to the relative impact on climate based on the specific form of ice nucleation.

To shed some light on this mystery, the ARM Facility will host a suite of guest instruments at its Southern Great Plains (SGP) site from April to June as part of the SGP Ice Nuclei Characterization Experiment, led by Colorado State University’s Paul DeMott. Together with measurements from ARM’s existing in situ and remote sensing instrumentation, scientists will use the combined data to quantify the types of ice nucleating particles present under various scenarios.

The SGP site is an ideal location to for exploring the natural and human-caused contributions of ice nucleating particles. The site lies within an agricultural region where soil is tilled and disturbed by windstorms. In addition, the SGP experiences long-range transport of dust particles from Asia and the U.S. Southwest, as well as smoke particles from Mexico and other regions. This creates an area with a diverse population of particles for analysis.

These are the first-ever ice nucleating particle measurements taken at the SGP site and may serve as a trial for long-term measurements. For more information, visit the field campaign abstract.