Measurement Report: An investigation of the spatiotemporal variability of aerosol in the mountainous terrain of the Upper Colorado River Basin from SAIL-Net

Abstract. In the Western US and similar topographic regions across the world, precipitation in the mountains is crucial to the local and downstream freshwater supply. Atmospheric aerosols can impact clouds and precipitation by acting as cloud condensation nuclei (CCN) and ice nucleating particles (INP). Previous studies suggest there is increased aerosol variability in these regions due to the complex terrain, but none have quantified the extent of this variability. In fall 2021, Handix Scientific contributed to the US Department of Energy (DOE)-funded Surface Atmosphere Integrated field Laboratory (SAIL) in the East River Watershed (ERW), CO, USA by deploying SAIL-Net, a novel network of six aerosol measurement nodes spanning the horizontal and vertical domains of SAIL. The ERW is a topographically diverse region where single measurement sites can miss important observations of aerosol-cloud interactions. Each measurement node included a small particle counter (POPS); a miniature CCN counter (CloudPuck); and a filter sampler (TRAPS) for INP analysis. SAIL-Net studied the spatiotemporal variability of aerosols and the usefulness of dense measurement networks in complex terrain. After the project’s completion in summer 2023, we analyzed the data to explore these topics. We found increased variability compared to a similar study over flat land. This variability was correlated with the elevation of the sites, and the extent of the variability changed seasonally. These data and analysis stand as a valuable resource for continued research into the role of aerosols in the hydrologic cycle and as the foundation for the design of measurement networks in complex terrain.