Breakout Summary Report

ARM/ASR User and PI Meeting

19 - 23 March 2018

Session Title: ARM Aerosol Measurement Strategy and ASR Measurement Needs
Session Date: 21 March 2018
Session Time: 10:30 AM - 12:30 PM
Number of Attendees: 77
Summary Authors: Jim Mather, Allison McComiskey, Doug Sisterson, Nicole Riemer, Jim Smith

Breakout Description

The goal of this session was to continue an ongoing effort to improve the degree to which ARM is providing measurements and data products that meet the needs of the ARM aerosol science user community. The session was focused on measurements from the ground-based Aerosol Observing Systems (AOS).

Jim Mather opened the session by providing an overview of the motivation for the session. The key issue is that there appears to be an underutilization of ground-based aerosol measurements based on file download statistics and publications. This issue, coupled with anecdotal reports of concerns about finding or using ARM aerosol measurements, led to the convening of a workshop in February 2017 by the Aerosol Measurement and Science Group (AMSG). Allison McComiskey, the science user co-chair of the AMSG, provided a summary of the 2017 AMSG workshop including recommendations for ARM to take to improve aerosol measurements. That report is available from the AMSG web page: https://www.arm.gov/about/constituent-groups/amsg.

Jim Mather followed Allison’s talk with an overview of the steps ARM is planning to take to address the issues raised at the AMSG workshop. These steps are captured in more detail in a measurement plan that will be made available soon. This plan is meant to be a living document and the expectation is that feedback from the community will be used to update the plan on a periodic basis.

There did not appear to be concern about any of the proposed activities except for the creation of a unified size distribution from three ARM instruments: the SMPS, UHSAS, and APS. There were concerns that combining the output from these instruments could be misleading: they measure size differently, we would need to ensure that we were within the counting range of each instrument, and we should properly account for inlet losses, especially for large particles. However, the consensus seemed to be that there is a need for a unified size distribution and that it would be better for experts within the ARM/ASR community to construct the distribution than to force individual scientists to do this.

These talks on the work of the AMSG and plans by ARM were followed by a pair of talks by Jim Smith and Mark Flanner that provided perspectives on the aerosol measurement needs of the ASR Aerosol Processes Working Group and the climate modeling community respectively.

Jim broke down the measurement needs of the Aerosol Processes Working Group by listing specific measurement needs for each of four sub-groups: New Particle Formation, Aerosol Life Cycle and Properties, Radiative Properties of Absorbing and Carbonaceous Aerosols, and properties and processes associated with Secondary Organic Aerosols.

Mark Flanner followed with the large-scale modeling perspective. He noted that important characteristics of measurements for modelers include that they have good spatial coverage, have good temporal coverage, or assist with process understanding. It is also important that data have quality labels to understand how the data should be used and that they be packaged in a convenient way. Finally, it would be helpful for data products to be constructed in such a way that they constrain parametric relationships.

Main Discussion

Following the presentations, there was quite a bit of discussion. In addition to concerns about constructing a unified size distribution mentioned above, topics discussed included:

• A suggestion that ARM would benefit by setting up a science project associated with one or more sites that focused research attention on those sites.
• Options for obtaining vertical profiles including remote sensing (especially lidar and passive radiometry), Unmanned Aerial Systems, and towers. Generally, there seemed to be a lot of interest for obtaining vertical profiles (including absorption), but there was not a clear path for doing so (though it seemed clear we should be making better use of our lidars).
• Interest was expressed in the full size distribution for study of Ice Nucleating Particles and in the HT-DMA because of its potential to provide information about hygroscopicity, CCN propensity, and species identification.
• There was interest in using filter measurements as a way of providing composition information. There seemed to be support for partnering with the IMPROVE network as well as for establishing our own filter-sampling protocol.
• The need to do a better job communicating capabilities and protocols (e.g., calibration).

Action Items

• Follow up with notes and questionnaire to meeting participants .
• Publish ARM aerosol measurement plan.
• Provide a unified description of ARM aerosol measurements that span both in situ and remote-sensing capabilities.
• Reach out to European aerosol measurement community to get ideas for best practices, for example, with regard to synthesizing unified size distributions.
• Reach out to the global aerosol modeling community (e.g., E3SM and AEROCOM).
• Plan a follow-up workshop (could be virtual) with the AMSG and other scientists in FY2019 to continue moving forward this community discussion.