21 Jun 2022
21 Jun 2022
Status: this preprint is currently under review for the journal ACP.

Using Aircraft Measurements to Characterize Subgrid-Scale Variability of Aerosol Properties Near the ARM Southern Great Plains Site

Jerome D. Fast1, David Bell1,2, Jiumeng Liu1,3, Fan Mei1, Georges Saliba1,4, John E. Shilling1, Kaitlyn Suski1,5, Jason Tomlinson1, Jian Wang6, Rahul Zaveri1, and Alla Zelenyuk1 Jerome D. Fast et al.
  • 1Pacific Northwest National Laboratory, Richland, Washington, USA
  • 2Paul Scherrer Institute, Villigen, Switzerland
  • 3School of Environment, Harbin Institute of Technology, Harbin, China
  • 4California Air Resources Board, Sacramento, California, USA
  • 5Juul Labs, San Francisco, California, USA
  • 6Washington University in Saint Louis, Saint Louis, Missouri, USA

Abstract. Complex distributions of aerosol properties evolve in space and time as a function of emissions, new particle formation, coagulation, condensational growth, chemical transformation, phase changes, turbulent mixing and transport, removal processes, and ambient meteorological conditions. The ability of chemical transport models to represent the multi-scale processes affecting the lifecycle of aerosols depends on their spatial resolution since aerosol properties are assumed to be constant within a grid cell. Subgrid-scale-dependent processes that affect aerosol populations could have a significant impact on the formation of particles, their growth to cloud condensation nuclei (CCN) sizes, aerosol-cloud interactions, dry deposition and rainout, and hence their burdens, lifetimes, and radiative forcing. To address this issue, we characterize subgrid-scale variability in terms of measured aerosol number, size, composition, and CCN concentrations made by repeated aircraft flight paths over the Atmospheric Radiation Measurement (ARM) program’s Southern Great Plains (SGP) site during the Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystem (HI-SCALE) campaign. Subgrid variability is quantified in terms of both normalized frequency distributions and percentage difference percentiles using grid spacings of 3, 9, 27, and 81 km that represent those typically used by cloud-system resolving models as well as the current and next generation climate models. Even though the SGP site is a rural location, surprisingly large horizontal gradients in aerosol properties were frequently observed. For example, 90 % of the 3, 9, and 27 km cell mean organic matter concentrations differed from the 81 km cell around the SGP site by as much as ~46 %, large spatial variability in aerosol number concentrations and size distributions were found during new particle formation events, and consequently 90 % of the 3, 9, and 27 km cell mean CCN number concentrations differed from the 81-km cell mean by as much as ~38 %. The spatial variability varied seasonally for some aerosol properties, with some having larger spatial variability during the spring and others having larger variability during the late summer. While measurements at a single surface site cannot reflect the surrounding variability of aerosol properties at a given time, aircraft measurements that are averaged within an 81-km cell were found to be similar to many, but not all, aerosol properties measured at the ground SGP site. This analysis suggests that it is reasonable to directly compare most ground SGP site aerosol measurements with coarse global climate model predictions. In addition, the variability quantified by the aircraft can be used as an uncertainty range when comparing the surface point measurements to model predictions that use coarse grid spacings.

Jerome D. Fast et al.

Status: open (until 02 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-384', Anonymous Referee #1, 23 Jun 2022 reply

Jerome D. Fast et al.

Jerome D. Fast et al.


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Short summary
Recent aircraft measurements from the HI-SCALE campaign conducted over the Southern Great Plains (SGP) site in Oklahoma are used to quantify spatial variability of aerosol properties in terms of grid spacings typically used by weather and climate models. Surprisingly large horizontal gradients in aerosol properties were frequently observed in this rural area. This spatial variability can be used as an uncertainty range when comparing surface point measurements to model predictions.