Breakout Summary Report


ARM/ASR User and PI Meeting

TRacking Aerosol Convection interactions ExpeRiment (TRACER)
24 October 2022
1:30 PM - 3:30 PM
Michael Jensen, Chongai Kuang, Heath Powers, Nathan Wales, Pavlos Kollias, Olga Mayol-Bracero, Maria Zawadowicz, Jiwen Fan

Breakout Description

During the ARM TRacking Aerosol Convection interactions Experiment (TRACER) a comprehensive data set of aerosol, cloud, precipitation, thermodynamics, and radiation was collected in an urban-coastal environment to improve our understanding of aerosol and cloud life cycle, the interaction of aerosol and convective clouds, and the influence of coastal and urban circulations on these processes. The breakout session focused on summarizing the diverse and unique data sets collected during the campaign and a community model intercomparison plan, followed by a discussion of collaborative research.

The session included several short, invited presentations summarizing some of the data sets collected during the TRACER campaign with a focus on defining opportunities and needs for research activities.

1:30–1:50 Michael Jensen/Chongai Kuang – “An overview of TRACER (+) Science and Operations”

A brief overview of the campaign’s cross-cutting motivations and high-level science questions, the TRACER measurement siting, partner agency campaigns, and the daily TRACER operations during the intensive operational period were presented. This was followed by 26 single-slide research and measurement summaries from the extended TRACER science team. More than 30 TRACER-related posters will be presented during the meeting.

1:50–2:10 Pavlos Kollias – “Preliminary analysis of CSAPR2 convective cell tracking observations during TRACER”

The motivation for the use of automated radar cell-tracking, a description of the algorithm implemented during the TRACER campaign, and some preliminary analysis of the statistics of cell-tracking operations (e.g., scans performed, number of cell samples, locations and diurnal cycle of cell sampling, cell sampling durations). Some examples of the characteristics of individual cell tracks were presented. 

2:10–2:30 Olga Mayol-Bracero/Maria Zawadowicz/ Chongai Kuang – “ARM AOS Aerosol Observations during TRACER”

An overview of the ARM Aerosol Observing System (AOS) and the AOS mentor team was shared followed by an overview of ongoing research activities using AOS observations of aerosol composition collected during TRACER. In addition, a preliminary analysis of observations highlighting new-particle formation events was shared.

2:30–2:50 Jiwen Fan – “Planned TRACER modeling activities”

Plans for a model intercomparison project (MIP) focused on a couple of well-observed case from TRACER were presented. This will follow on and improve the recently published, motivational MIP from the Aerosol, Clouds, Precipitation and Climate (ACPC) working group. A proposed approach and model setup was presented along with a discussion of the criteria for choosing golden cases to focus on, simulation types, model output, and evaluation using observations.

Main Discussion

While there was not a lot of time for discussion, the main questions that came up were related to timelines for value-added products and PI products especially from the cell-tracking results, the aerosol analyses and a few of the higher-order value-added products, and an integrated product with meteorology, cloud/precipitation, and aerosols. The discussion of modeling activities also generated discussions regarding how additional investigators can participate in the MIP, and other modeling activities and approaches of interest of the larger TRACER science team.

Key Findings

Thanks to the efforts of the extended ARM operations team, including the site operations team, ARM mentors, and software developers in addition to the TRACER science team, a very complete data set was collected over the course of the TRACER campaign. By all accounts, this should be an excellent data set to address the science questions outlined in the TRACER proposal and science plan, and several other science questions about aerosol processes, cloud processes, aerosol-cloud interactions, and how each of these is impacted by the coastal-urban environment. In addition to the interest in the radar and aerosol data sets that were presented, there was interest in results from efforts to quantify the synoptic, mesoscale (sea-breeze), and aerosol regimes to provide context for the detailed ARM and ASR measurements.


Just a few weeks after the end of the data collection period, there were not many issues identified. For investigators using radiosonde measurements for quantitative studies, caution was urged when using different radiosonde types. At least three different types of radiosondes were used across the TRACER science team and there are some differences among them. There was some discussion of a radiosonde homogenization exercise to help alleviate these issues.


Some investigators will require high-order VAPS, PI products, and data from guest instruments (which will be due to the ARM Data Center at the end of March). There is also a need for new products (likely from PIs) integrating meteorological, cloud/precipitation and aerosols particularly aligned with convective cells. To address some of the TRACER science questions, coordinated modeling efforts will need to be undertaken with appropriate funding.


No new decisions were made during the breakout session.

Future Plans

The TRACER modeling group plans to organize the TRACER MIP if funding allows. Plans were mentioned for a spring TRACER Science and Operations workshop, a campaign overview manuscript for submission to BAMS sometime in the first half of 2023, and a MIP focused on one or more TRACER cases.

Action Items

No new action items were identified during the breakout session.