Breakout Summary Report

ARM/ASR User and PI Meeting

19 - 23 March 2018

Session Title: Secondary organic aerosols - forging connections between process observers and process modelers
Session Date: 19 March 2018
Session Time: 1:30 PM - 3:30 PM
Number of Attendees: 39
Summary Authors: Riemer, Fast, Thornton

Breakout Description

The ASR community has made great progress in experimental studies of detailed processes relating to SOA formation and evolution. However, quantifying the impact of such processes under atmospherically relevant conditions within an appropriate modeling framework remains difficult and time-consuming. A concerted effort to provide “test beds” for modeling that would facilitate testing the impact of experimental process-level results would therefore be very useful. The goal of this breakout session is to bring together modelers and experimentalists to work towards creating a modeling test bed that can be used to 1) quantify and demonstrate impacts of (SOA-related) processes measured in the lab or field and 2) quantify and understand the differences among various approaches in representing SOA-related processes. 


Main Discussion

We had invited short presentations by experimentalists (Joel Thornton, Lindsay Yee, Jose Jimenez) and modelers (Camille Mouchel-Vallon, Manabu Shiraiwa, Manish Shrivastava) 
on their vision of a modeling test bed, and a report on already existing test bed concepts at PNNL by Jerome Fast and Rahul Zaveri.
After their presentations, the group discussed if it is feasible and/or desirable to have a test bed capability that would facilitate testing the impact of experimental process-level results. Right now the existing codes are not as “user friendly” as one might hope, and sometimes not publicly available (open source, on GitHub, with version control).

Key Findings

The complexity associated with implementing new SOA processes varies widely--from changing the values of some coefficients in an existing chemistry code to making changes in many modules in a 3D modeling framework such as WRF-Chem to capture feedbacks. In does not seem practical to try and design a test bed that is suitable for all needs. Instead, a case-by-case approach seems more appropriate. Implementing processes that require a lot of new code development or adjustments of existing code will always require collaboration with an experienced modeler. However, for cases where the changes are small (e.g., changing certain parameters in existing model representations), the test bed would facilitate progress.

The PNNL MOSAIC model was proposed to serve as a test bed prototype. It exists as a box model and embedded within WRF-CHEM and treats relevant aerosol processes already, which are important because the organic chemistry is not occurring in isolation. A serious limitation at the moment is, however, that it does not exist as an open source code.

Issues

Some experimentalists expressed that it can be difficult to identify the “right” modeler (i.e., someone with a modeling tool that can accommodate the processes under investigation). Some sort of “speed dating approach” was suggested to find the right match.

Needs

N/A

Decisions

N/A

Future Plans

• An open source version of MOSAIC should be made available where end users can alter processes or parameters.
• This would aid the development of a user community within ASR and beyond to maintain ASR leadership in SOA process and property science discovery and impact assessment.

Action Items

• Identify test cases for various processes/properties and test users, hold an informal workshop with these users to practice dissemination and training
• Timeframe: within next year complete the dissemination and training to a few users currently funded by ASR
• Follow up at next ASR meeting to discuss formalizing practice for broadening to wider community.