Sampling Mixed-Phase Clouds at Storm Peak Laboratory using the Phase Separation Inlet for Droplets Ice Residuals and Interstitial Aerosols (SPIDER)

Mixed phase clouds (MPCs) are ubiquitous and can influence radiative energy budgets, cloud electrification, and precipitation regionally and globally. Despite their importance, few studies have comprehensively looked at the droplet and ice microphysical processes of MPCs. In this case study, we tested the phaSe seParation Inlet for Droplets icE residuals and inteRstitial aerosols (SPIDER) at Storm Peak Laboratory (SPL) in the Rocky Mountains of the western US, where MPCs are frequently present. SPIDER uses an omni-directional inlet, a large-pumped counterflow virtual impactor, an evaporation chamber, and a pumped counterflow virtual impactor that can simultaneously separate interstitial aerosols, cloud droplets and ice crystals, therefore allowing for an in-depth analysis of MPCs. During the study period, background ice crystal residual concentrations at SPL were measured and compared between clear and cloudy periods. SPIDER’s ice crystal channel picked up changes in the number density and size distribution of ice crystal residuals, reflecting a preference for ice residuals larger than 200 nm. Cloud droplet residuals were also detected by SPIDER, but we were unable to draw quantitative results due to the lower resolution of the optical particle counter. Future experiments with SPIDER should include higher range and resolution optical particle counters to be able to detect cloud droplet and ice crystal residual size distributions and counts.