Seasonal Differences in New Particle Formation Events in Crested Butte, Colorado during the SAIL Campaign

ANNA KAPP, James Smith, Celia Faiola, Maria Flores, Univeristy of California, Irvine

     Abstract Number: 268
     Working Group: Aerosols, Clouds and Climate

Abstract
Climate change is intensifying droughts across the globe. Of particular interest is the effect of drought on mountain regions. Mountain rivers are often used for irrigation in areas that receive little rainfall. Reduced precipitation in the mountains has far reaching effects on surrounding regions. Precipitation cannot occur if clouds do not form, and cloud formation is promoted by the presence of cloud condensation nuclei (CCN) in the air. The Surface Atmosphere Integrated Field Laboratory (SAIL), a DOE-funded field campaign in Crested Butte, Colorado, was dedicated to studying how interactions between the earth and the atmosphere affect precipitation in mountain regions. During SAIL, new particle formation (NPF), one of the main sources of CCN, was frequently observed. Strong seasonal trends were observed in the frequency and characteristics of NPF events, which we examine in this study.

Data on NPF events was collected during 1 September 2021 until 15 June 2023 from an Aerosol Chemical Speciation Monitor (ACSM), Scanning Mobility Particle Sizer (SMPS), Cloud Condensation Nuclii (CCN) counter, and Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA). Airmass back trajectories were calculated using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and snowmelt data was collected from a nearby Snowpack Telemetry (SNOTEL) site. Before snowmelt, NPF almost exclusively occurred when the wind was from the north. We believe that these events were caused by transport of sulfur compounds from a coal fire power plant located in Northern Colorado. Immediately after snowmelt, there was a one-month period where NPF occurred almost daily. During this time, ACSM data showed that the mass concentration of total organics in aerosols greatly increased. We believe that the regular occurrence of NPF events after snowmelt was driven by increased biogenic emissions due to spring plant growth.