Breakout Summary Report

ARM/ASR User and PI Meeting

13 - 17 March 2017

Session Title: CMDV-MCS
Session Date: 15 March 2017
Session Time: 1:30 PM - 3:30 PM
Number of Attendees: 30
Summary Authors: Steve Ghan

Breakout Description

The purpose of the CMDV-MCS session is to brainstorm with the ARM/ASR community about project foci and measurement data that could help with the project. We had six 15-min presentations and a 30-min discussion. The discussion was very helpful to the project. Also, a few people talked with us about collaboration after the session during the meeting period. For example, Yolande Serra from UW, Guang Zhang from UCSD, and Craig Ferguson from SUNY, Albany. Therefore, it was a successful and useful session to our project.

Main Discussion

• Could the polynomial coefficients for the representation of the hydrometeor size distribution affect reflectivity? It is a metric. We decided to use this metric in the test w/ the piggyback configuration in WRF.
• Which version of SBM is better for use in the CMDV project? Does complexity (including liquid on ice) matter for project metrics, such as precipitation intensity, integrated precipitation, propagation, storm longevity, cloud radiative forcing? Khain’s presentation shows Fast SBM with graupel option does not work well for simulating MCS convective structure and precipitation. However, the hail version does not show good results in stratiform. We need a full SBM to do well in both, but it is too expensive for GCM. So, we need to compromise with some focused features such as convective precipitation and structure, which is key to MCS propagation and maintenance.
• Use ACME in CAPT mode to test new physics.
• Initiation of ACME CAPT simulations. Need to isolate convection initiation over mountains from subsequent convection propagation eastward. To test propagation physics best to initialize with realistic convection over mountains. Reanalysis resolution (3 km) is marginal. Better to run LAM at 1.8 km for 12 hours to initiate convection. Then calculate subgrid variance of w over ACME grid cells to initialize CLUBB TKE.
• We discussed which types of MCSs we should focus on, propagating convection versus local initialized system. Since we are not developing a physical treatment for initiation, the local systems might not be generated well, so we should focus on propagating MCSs. We also discussed choosing a case or two to start with. MC3E May 20 and April 24-25, and PECAN June 27, could be the candidates, but further check on observational data is needed to make a decision.
• Errors due to poor initiation and transition from shallow to deep convection. We do not have new physics to improve local initiation or transition, so local initiated systems and transition from shallow to deep convection are not our targets.
• A few people are interested in collaborating with CMDV-MCS project in evaluating MCSs in ACME, using our LAM/LES data, etc. (such as Yolande on providing data for MCS evaluation over GoAmazon, Guang on using LAM data to analyze MCS propagation).

Key Findings

• ACME-SP-ECPP is working properly
• PECAN has more propagating systems than MC3E
• Need about 6 coefficients for the polynomial fitting of the PSD from SBM for each mode, which may not save computer time substantially.

Issues

• Need to talk to Peter Caldwell about CMDV-SW cloud microphysics focus. MG2 or P3?
• Need to decide a case to start with. Need to have observational team to check the candidate cases for data availability and then select 1-2 cases to start with.

Needs

• Computer time!
• More actively advertise the developments in both model and observational data from our projects. Many people still do not have an idea about the project.

Decisions

• Use ACME in CAPT mode to test new physics
• Focus on propagating MCSs only. Select a case or two to start.
• GigaLES should focus on propagating MCSs.

Future Plans

• We will continue to organize sessions for the project in AGU and the next ARM/ASR meeting. It is useful to have more people engage with the project.

Action Items

• Steve and Vince talk to Pete Bogenschutz about his previous attempt to treat horizontal advection of CLUBB higher moments.
• Jiwen and Steve talk to Peter Caldwell about CMDV-SW cloud microphysics focus.
• Observation team decide a case or two to start with.