Agricultural Ice Nuclei at SGP
1 September 2021 - 31 May 2022
Lead Scientist: Susannah Burrows
Ice-nucleating particles (INPs) in the atmosphere trigger freezing of liquid cloud droplets at warmer temperatures than freezing would occur for pure water, impacting the cloud development in ways that can alter the formation of precipitation and the transfer of solar and thermal energy through the clouds. Particles with different physical and chemical characteristics have differing abilities to act as INPs, and their concentrations in the atmosphere vary with time and location. The aim of the proposed field campaign deployment is to collect observations that can be used to understand the drivers of variability in observed INP concentrations at the SGP site, which are thought to originate in part from regional emissions of fertile, agricultural soils containing high organic content. In addition to INPs associated with soils, there are many other possible sources of INPs at the site, including aerosol arising from controlled burns or wildfires, inorganic desert dust from long-range transport, cellulose-containing plant matter, fungal spores, and microbial particles. To distinguish these different potential sources of INPs, we will deploy a unique instrument from DOE’s Environmental and Molecular Science Laboratory (EMSL), the single-particle mass spectrometer, miniSPLAT, in combination with EMSL’s ice nucleation chamber. We will further deploy two additional ice nucleation chambers, i.e., the Continuous Flow Diffusioin Chamber (CFDC), and the Portable Ice Nucleation Experiment (PINE). Additionally, we will collect particle samples in different size ranges for offline analyses, taking advantage of EMSL’s molecular imaging and characterization capabilities. Finally, we will deploy an aerosol fluorescence instrument (WIBS) to observe the contribution of fluorescent biological aerosol particles to the aerosol at SGP, and investigate correlations between these particles and INPs. Surrounded by agricultural land, the ARM user facility’s Southern Great Plains (SGP) observatory in Oklahoma is an ideal location for studying the impacts of soil organic particles on atmospheric INP concentrations. Most emissions of agricultural soils occur in association with tilling and harvesting operations, and the campaign will target a time period that coincides with those activities. This campaign will characterize in unprecedented detail the INPs generated during active agricultural operations and will provide new insights into the impacts of agricultural operations on the variability of INP concentrations in the atmosphere.