CPA

Cloud processing of aerosol during SAIL

30 September 2021 - 15 June 2023

Lead Scientist: Swarup China

Observatory: AMF (ARM Mobile Facility 2) - GUC

Cloud processing of aerosol during SAIL

Cloud processing of aerosols produces aerosols with dramatically different physicochemical properties than their original form. Cloud processing may transform particles into efficient cloud condensation nuclei (CCN) or ice nucleating particles (INP) that can further participate in cloud formation. We propose to study cloud processing of aerosol during the SAIL field campaign using multi-modal offline analysis techniques available at DOE’s user facility, the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory. The main scientific aim of this project is to understand the processes that transform aerosols (chemically and physically) and influence aerosol-cloud interactions. Aerosol particles undergo significant modifications due to warm (cloud droplets) and cold cloud (ice crystals) processing. Cloud processing of aerosol has important effects on the atmospheric aerosol number and mass concentration, size distribution, phase separation, and chemical composition.

Detailed size-resolved chemical composition of aerosols and their microphysical properties along with in situ measurements from ARM’s mobile facilities will improve our understanding of aerosol-cloud processes. Aerosol samples will be collected using the newly developed automated Size-and-Time-resolved Aerosol Collector (STAC). Determining size-resolved chemical composition of particles is crucial for understanding several atmospheric processes during different seasons, but challenging to accomplish due to lack of long-term measurements. The revised version of STAC is modified for long-term ground-based measurements, so it can collect samples for month without maintenance. The automated sampler will enable collection of samples within a broad size range (0.05-5.0 µm) and will provide long-term collection of samples to fill the current measurement gap at the ARM observatory site. We will analyze aerosol samples using EMSL’s microscopy, spectroscopy, and mass spectrometry platforms. Cloud-processing-induced transformation can result in specific changes in the physical and chemical properties of the aerosol. This project will provide a better representation of cloud-processing treatment and contribute to better representations of cloud-processed aerosols by providing size-resolved chemical composition and mixing state-based indices.