Katie Rocci joined us this year and writes: "I worked in Sonia Kreidenweis' group under Tom Hill and Christina McCluskey. I am from Newmarket, New Hampshire and attend the University of New Hampshire. I am a double major in Environmental Science with an Ecosystems focus and Earth Science with a Climate focus. My research interests are biogeochemical cycles and how they are affected by the changing climate but at CMMAP I studied something rather different. "Did you know water doesn't generally freeze by itself? I didn't, until I studied ice nucleating particles (INPs) at CMMAP this past summer. "INPs are essentially little bits of stuff (dust, sea spray, biological particles, etc.) that catalyze freezing at warmer than average temperatures. What is an "average" temperature? Without anything to catalyze the freezing, pure water will freeze at approximately -36°C. "So, why do INPs matter? They affect precipitation processes as well as cloud forcing, and thus affect model outcomes. "For my project I characterized INPs at a site in Bodega Bay, California. I used data collected on site to determine the dominant aerosol type in 64 filters collected during the field campaign in January-March, 2015. After characterizing each filter I ran a variety of filters on CSU's Ice Spectrometer (IS) to determine INP number concentrations. I also heat-treated a few filters and re-ran them on the IS to look at the contribution of biological labile INP to the INP spectrum. Lastly, I ran HYSPLIT back trajectories to determine the origin of air masses affecting filters. "We found that filters collected over open ocean exhibit significantly smaller INP number concentrations than those collected at the coast. This could be due to aerosol loading, which we have yet to normalize for. However, it appears than an ocean-specific INP parameterization is needed within models. "I really loved Colorado and Fort Collins and all of the outdoorsy things we did! Hopefully, I'll be back soon!" Katie's poster, Characterization of Ice Nucleating Particles at the Western US Coast, may be found here.