Understanding contributions of agricultural dust to vertical profiles of ice-nucleating particles in the central Great Plains
EMSL Project ID
51910
Abstract
Agricultural dusts contribute to airborne particulate amount, aerosol optical depth, and atmospheric ice-nucleating particle (INP) concentrations in agricultural regions. Agricultural dusts include a significant number of supermicron particles, which contribute disproportionately to near-surface INP concentrations due to their large surface areas. A question of considerable research interest has been how efficiently dust particles are mixed within the convective boundary layer, and therefore whether they can contribute significantly to the INPs that are available to clouds forming at the top of the convective boundary layer (CBL) and above, especially in the supermicron particle size range.The newly developed automated Size and Time-resolved Aerosol Collector (STAC), flying on the ARM Tethered Balloon System (TBS), is perfectly positioned to address these research questions. This project will deploy the STAC+TBS to sample particles throughout the convective boundary layer at the Southern Great Plains. These samples will be chemically characterized at the Environmental and Molecular Sciences Laboratory (EMSL) using scanning electron microscopy (SEM) to classify particles based on their elemental composition. This will produce a size-resolved measurement of the concentration of different particle types, including dusts, present at different altitudes in the convective boundary layer.
The project will aim to understand dust variability at two temporal scales: seasonal and day-to-day variability. Samples collected during a single season will be used to understand day-to-day variability. Observed dust amount will be compared with model predictions of dust amount and its vertical profile in order to evaluate whether airmasses with greater residence time over agricultural tillage dust source regions are associated with greater concentrations of observed dust. Samples will also be collected across four seasons to evaluate whether seasonal differences in agricultural tillage are reflected in dust concentrations measured at the SGP site.
The project will also evaluate whether dust particles are the primary contributors to INPs at all sampled altitudes within the convective boundary layer, using both a bottom-up and a top-down approach to test this hypothesis. First, the size-resolved particle composition measured by the IN-ESEM will be used to develop a bottom-up estimate of the contributions of different particle types to atmospheric INPs. Additionally, in a top-down approach, the project will use the ice nucleation environmental scanning electron microscope (IN-ESEM), a unique EMSL capability, to identify which particles initiate the onset of freezing in collected samples, and to chemically characterize and classify those particles.
Taken together, results from this project will contribute to advancing scientific understanding of the impacts of agricultural dust on INPs available to clouds, their seasonality, and their vertical distribution in the CBL.
Project Details
Project type
FICUS Research
Start Date
2021-10-01
End Date
N/A
Status
Active
Released Data Link
Team
Principal Investigator
Co-Investigator(s)