Breakout Summary Report

ARM/ASR User and PI Meeting

Breakout Description

The ASR Aerosol Working Group and ARM Aerosol Measurement Science Group have had sustained discussions with the PI teams over several years as to what the priority science directions are in aerosol science that meet the EESSD mission and how to best meet that science with ARM measurements that are accessible to the user community. While much attention has focused on the instrumentation suite deployed during campaigns, choices in sampling are equally important for producing observations that can advance our scientific understanding of key aerosol processes and target the most current knowledge gaps. This session will focus on three aspects of aerosol sampling: 1) single-point versus distributed sampling, 2) continuous operation versus intensive operation periods, and 3) bulk versus single-particle analysis. Discussions around the contrasts between different modes of these aspects of sampling will clarify the benefits and logistical challenges in implementing new approaches in each of these areas and how combinations of different approaches might optimize scientific applications.

Main Discussion

The ASR Aerosol Working Group and ARM Aerosol Measurement Science Group have had sustained discussions with the PI teams over several years as to what the priority science directions are in aerosol science that meet the EESSD mission and how to best meet that science with ARM measurements that are accessible to the user community. While much attention has focused on the instrumentation suite deployed during campaigns, choices in sampling are equally important for producing observations that can advance our scientific understanding of key aerosol processes and target the most current knowledge gaps. Discussions around the contrasts between different sampling modes will clarify the benefits and logistical challenges in implementing new approaches in each of these areas and how combinations of different approaches might optimize scientific applications.

The session was organized to provide the PI team information on recent activities of the ARM constituent Aerosol Measurement Science Group (AMSG) and to solicit feedback on how advancing design and methods of aerosol sampling might promote data use and applicability to current science drivers. The leads of the AMSG technical sub-groups first presented overviews on discussions that the AMSG has had on approaching measurement techniques, quality, modeling, and sampling. Each of these generated further discussion

Key Findings

Discussion during the first block reviewing and soliciting input on ongoing AMSG activities resulted in some input on data quality, missing measurements, and products for interfacing with models.

Quality: A need to do long-term reanalysis of filter measurements of aerosol absorption was expressed as we expect to move on to new methods for absorption measurements.  (see Kumar et al. Atmos. Meas. Tech., 15, 4569–4583, 2022, https://doi.org/10.5194/amt-15-4569-2022 for the new technique.)

Measurements: Desire to have expanded measurements at the NSA sites and to have easy access to NOAA and ARM data together. While there was a strong desire to continue routine measurements, VOC and NOx measurements are still also desired. There is acknowledgement that these can be more intensive measurements to make, however some newer methods are simpler and should be considered, including cavity ringdown (Aerodyne).

Modeling: Discussion on the need to reconcile single particle analyses and modeling with mixing state in coarser-scale models. Would be good to target progress in the next 3-5 years. Two things are needed – one is much more spatially widespread single particle observations and the other is developing and approach to relating these data to the quantities that coarser-scale models represent. The latter is a particularly challenging problem that is currently being worked on. We also need to consider building modeling best estimate products and also potentially bundles for evaluation.

Discussions during the second block showed support for expanding concepts of aerosol sampling and continuing in some particular directions within the three proposed sampling modes:

IOPs: There was wide support for the general concept of developing some kind of intensive observation periods for aerosol measurements at fixed sites and potentially even within mobile deployments. SGP was used as a target for exploring how it might work and some ideas were put forth including using upcoming Arctic Shark flights to rally around or developing research themes that would include a preponderance of instrumentation allowing for more detailed characterization of aerosol properties and more impactful science questions answered. There was clarification that this concept would go beyond what exists with small ARM campaigns that supplement fixed sites or AMF deployments by providing organization around a particular research theme, site, and time period to broaden participation by the larger community and bring in more state-of-the-art instrumentation simultaneously to one place. Jeff Stehr raised the issue of whether support for more complex, typically PI-run instrumentation should continue through ASR or whether other potential solutions to having these expanded measurements available during ARM deployments could be explored, acknowledging that research resources are limited.

Distributed sampling: There was general support for implementing distributed sampling for the useful information it would provide. Discussion around the cost of sensors came up and that new, lower-cost and mid-range quality instruments can now provide a great baseline for some properties. But it was also noted that spatial information from advanced measurements are still needed and so making sure that more complex instrument suites made of guest instrumentation or mobile labs owned/operated by external organizations can be particularly valuable. The subject of Observing System Simulation Experiments (OSSE) came up with respect to developing sampling designs, potentially tapping into long-term/historical air quality forecasts or even LASSO as a way to implement design. It was commented that they would be particularly helpful in understanding what type and frequency of filter sampling would be the best investment to complement what we have with IMPROVE and our on-line measurements such as ACSM and SP2. There were questions as to how these design activities should be supported and how to ensure that they are done with consideration of the primary science objectives of ARM and ASR.

Single-Particle: This discussion was kicked off with an example of different model mixing-state representations and the notion that there is no path that currently exists to evaluate the very different results. Single-particle data are not widely used due to the disconnect between the information they provide and the related information that models use and produce but that is in a very different form. There is on-going work within our ranks to make this connection and there was strong sentiment that the payoff would be large and that we should stay this course. Beyond mapping information between models and measurements, there also needs to be mapping between different aerosol mass spectrometers, that can all produce information with different meaning. There was acknowledgement that the instrument-to-instrument and instrument-to-model mapping discussed here represents a long road but that aerosol mixing state is a key property that must be resolved and so this work requires that investment. There was a suggestion to connect with AeroCom for whom mixing state is not a priority just yet but they are moving in this direction and would benefit from more communication with experimentalists and single-particle modelers.

The Padlet app was used to collect input from breakout participants – a screenshot of the input is below:

Issues

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Needs

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Decisions

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Future Plans

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Action Items

The input received during the breakout will be reviewed by the AMSG and actions on specific topics will be prioritized.