Seasonal Aerosol Regimes and Processes Observed in Mountainous Terrain at Surface Atmosphere Integrated Field Laboratory (SAIL)

Description

Regional and transported aerosols can impact climate in many ways, e.g., through direct and indirect radiative impacts, surface deposition, land-atmosphere and aerosol-cloud-precipitation interactions. Within complex high elevation mountainous terrain like the East River Watershed Basin in Colorado, these interactions become more complicated due to orographic processes and how the particles are distributed within the boundary layer. Aerosol impacts in these regions are currently undercontstrained in models due to a lack of observations in these types of environments. As such, the goal of this work is to explore the properties of aerosol, absorbing aerosol, supermicron and bioaerosol events and their diurnal variabilities in Colorado during Surface Atmosphere Integrated Field Laboratory (SAIL). 

We present ambient aerosol data collected at two ground sites using the Aerosol Observing System (AOS), guest supermircon and bioaerosol instruments and vertical profiles from the Tethered Balloon Sonde (TBS) collected during the deployment of the ARM AMF2 to SAIL. In addition to the ARM measurements, we deployed instrumentation for the SAIL Supermicron Bioaerosol (SSB) campaign: two real-time particulate monitors (PM) in Gothic (AMF2 M1) and on Crested Butte Mountain (AOS, S2) to understand the submicron and supermicron differences at the two ARM sites and a real-time single-particle measurement of bioaerosols to investigate regional sources and ambient trends in the spring and summer. Preliminary analysis of the PM shows a diurnal cycle is observed at the lower elevation site (Gothic, elevation ~9,500) that is not present at the higher elevation site (Crested Butte Mtn., elevation ~10,300 ft). Overall correlations between the two sites during the different seasons will be presented to understand local sources and the larger-scale regional aerosol. Multi-day transport events of absorbing supermicron dust were observed by the AOS in the spring, which can impact surface radiation, snowmelt and surface hydrology when deposited on the snowpack. We highlight some of the observed atmospheric dust events in 2022 and 2023 along with weather patterns including precipitation to understand transportation to the surface via wet and/or dry deposition. We also deployed the real-time Wideband Integrated Bioaerosol Sensor (WIBS-NEO) in the summer of 2022 and spring of 2023 to investigate ambient trends in the physical properties of bioaerosol. To our knowledge, these are the first high‐time resolution measurements of bioaerosol made within mountainous terrain.